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-<!-- This document was created with Syntext Serna Free. --><chapter xmlns="http://docbook.org/ns/docbook" xmlns:xl="http://www.w3.org/1999/xlink" version="5.0" xml:lang="en-US" xml:id="lustreproc">
+<chapter xmlns="http://docbook.org/ns/docbook" xmlns:xl="http://www.w3.org/1999/xlink" version="5.0"
+ xml:lang="en-US" xml:id="lustreproc">
<title xml:id="lustreproc.title">LustreProc</title>
- <para>The <literal>/proc</literal> file system acts as an interface to internal data structures in the kernel. The <literal>/proc</literal> variables can be used to control aspects of Lustre performance and provide information.</para>
- <para>This chapter describes Lustre /proc entries and includes the following sections:</para>
+ <para>The <literal>/proc</literal> file system acts as an interface to internal data structures in
+ the kernel. This chapter describes entries in <literal>/proc</literal> that are useful for
+ tuning and monitoring aspects of a Lustre file system. It includes these sections:</para>
<itemizedlist>
<listitem>
- <para><xref linkend="dbdoclet.50438271_90999"/></para>
- </listitem>
- <listitem>
- <para><xref linkend="dbdoclet.50438271_78950"/></para>
- </listitem>
- <listitem>
<para><xref linkend="dbdoclet.50438271_83523"/></para>
+ <para>.</para>
</listitem>
</itemizedlist>
- <section xml:id="dbdoclet.50438271_90999">
- <title><indexterm><primary>proc</primary></indexterm>Proc Entries for Lustre</title>
- <para>This section describes <literal>/proc</literal> entries for Lustre.</para>
+ <section>
+ <title>Introduction to <literal>/proc</literal></title>
+ <para>The <literal>/proc</literal> directory provides an interface to internal data structures
+ in the kernel that enables monitoring and tuning of many aspects of Lustre file system and
+ application performance These data structures include settings and metrics for components such
+ as memory, networking, file systems, and kernel housekeeping routines, which are available
+ throughout the hierarchical file layout in <literal>/proc.</literal>
+ </para>
+ <para>Typically, metrics are accessed by reading from <literal>/proc</literal> files and
+ settings are changed by writing to <literal>/proc</literal> files. Some data is server-only,
+ some data is client-only, and some data is exported from the client to the server and is thus
+ duplicated in both locations.</para>
+ <note>
+ <para>In the examples in this chapter, <literal>#</literal> indicates a command is entered as
+ root. Servers are named according to the convention
+ <literal><replaceable>fsname</replaceable>-<replaceable>MDT|OSTnumber</replaceable></literal>.
+ The standard UNIX wildcard designation (*) is used.</para>
+ </note>
+ <para>In most cases, information is accessed using the <literal>lctl get_param</literal> command
+ and settings are changed using the <literal>lctl set_param</literal> command. Some examples
+ are shown below:</para>
+ <itemizedlist>
+ <listitem>
+ <para> To obtain data from a Lustre client:</para>
+ <screen># lctl list_param osc.*
+osc.testfs-OST0000-osc-ffff881071d5cc00
+osc.testfs-OST0001-osc-ffff881071d5cc00
+osc.testfs-OST0002-osc-ffff881071d5cc00
+osc.testfs-OST0003-osc-ffff881071d5cc00
+osc.testfs-OST0004-osc-ffff881071d5cc00
+osc.testfs-OST0005-osc-ffff881071d5cc00
+osc.testfs-OST0006-osc-ffff881071d5cc00
+osc.testfs-OST0007-osc-ffff881071d5cc00
+osc.testfs-OST0008-osc-ffff881071d5cc00</screen>
+ <para>In this example, information about OST connections available on a client is displayed
+ (indicated by "osc").</para>
+ </listitem>
+ </itemizedlist>
+ <itemizedlist>
+ <listitem>
+ <para> To see multiple levels of parameters, use multiple
+ wildcards:<screen># lctl list_param osc.*.*
+osc.testfs-OST0000-osc-ffff881071d5cc00.active
+osc.testfs-OST0000-osc-ffff881071d5cc00.blocksize
+osc.testfs-OST0000-osc-ffff881071d5cc00.checksum_type
+osc.testfs-OST0000-osc-ffff881071d5cc00.checksums
+osc.testfs-OST0000-osc-ffff881071d5cc00.connect_flags
+osc.testfs-OST0000-osc-ffff881071d5cc00.contention_seconds
+osc.testfs-OST0000-osc-ffff881071d5cc00.cur_dirty_bytes
+...
+osc.testfs-OST0000-osc-ffff881071d5cc00.rpc_stats</screen></para>
+ </listitem>
+ </itemizedlist>
+ <itemizedlist>
+ <listitem>
+ <para> To view a specific file, use <literal>lctl get_param</literal>
+ :<screen># lctl get_param osc.lustre-OST0000-osc-ffff881071d5cc00.rpc_stats</screen></para>
+ </listitem>
+ </itemizedlist>
+ <para>For more information about using <literal>lctl</literal>, see <xref
+ xmlns:xlink="http://www.w3.org/1999/xlink" linkend="dbdoclet.50438194_51490"/>.</para>
+ <para>Data can also be viewed using the <literal>cat</literal> command with the full path to the
+ file. The form of the <literal>cat</literal> command is similar to that of the <literal>lctl
+ get_param</literal> command with these differences. In the <literal>cat</literal> command: </para>
+ <itemizedlist>
+ <listitem>
+ <para> Replace the dots in the path with slashes.</para>
+ </listitem>
+ <listitem>
+ <para> Prepend the path with the following as
+ appropriate:<screen>/proc/{fs,sys}/{lustre,lnet}</screen></para>
+ </listitem>
+ </itemizedlist>
+ <para>For example, an <literal>lctl get_param</literal> command may look like
+ this:<screen># lctl get_param osc.*.uuid
+osc.testfs-OST0000-osc-ffff881071d5cc00.uuid=594db456-0685-bd16-f59b-e72ee90e9819
+osc.testfs-OST0001-osc-ffff881071d5cc00.uuid=594db456-0685-bd16-f59b-e72ee90e9819
+...</screen></para>
+ <para>The equivalent <literal>cat</literal> command looks like
+ this:<screen># cat /proc/fs/lustre/osc/*/uuid
+594db456-0685-bd16-f59b-e72ee90e9819
+594db456-0685-bd16-f59b-e72ee90e9819
+...</screen></para>
+ <para>The <literal>llstat</literal> utility can be used to monitor some Lustre file system I/O
+ activity over a specified time period. For more details, see <xref
+ xmlns:xlink="http://www.w3.org/1999/xlink" linkend="dbdoclet.50438219_23232"/></para>
+ <para>Some data is imported from attached clients and is available in a directory called
+ <literal>exports</literal> located in the corresponding per-service directory on a Lustre
+ server. For
+ example:<screen># ls /proc/fs/lustre/obdfilter/testfs-OST0000/exports/192.168.124.9\@o2ib1/
+# hash ldlm_stats stats uuid</screen></para>
<section remap="h3">
- <title>Locating Lustre File Systems and Servers</title>
- <para>Use the proc files on the MGS to locate the following:</para>
+ <title>Identifying Lustre File Systems and Servers</title>
+ <para>Several <literal>/proc</literal> files on the MGS list existing Lustre file systems and
+ file system servers. The examples below are for a Lustre file system called
+ <literal>testfs</literal> with one MDT and three OSTs.</para>
<itemizedlist>
<listitem>
- <para> All known file systems</para>
- <screen>mgs# cat /proc/fs/lustre/mgs/MGS/filesystems
-spfs
-lustre</screen>
+ <para> To view all known Lustre file systems, enter:</para>
+ <screen>mgs# lctl get_param mgs.*.filesystems
+testfs</screen>
</listitem>
- </itemizedlist>
- <itemizedlist>
<listitem>
- <para> The server names participating in a file system (for each file system that has at least one server running)</para>
- <screen>mgs# cat /proc/fs/lustre/mgs/MGS/live/spfs
-fsname: spfs
-flags: 0x0 gen: 7
-spfs-MDT0000
-spfs-OST0000</screen>
+ <para> To view the names of the servers in a file system in which least one server is
+ running,
+ enter:<screen>lctl get_param mgs.*.live.<replaceable><filesystem name></replaceable></screen></para>
+ <para>For example:</para>
+ <screen>mgs# lctl get_param mgs.*.live.testfs
+fsname: testfs
+flags: 0x20 gen: 45
+testfs-MDT0000
+testfs-OST0000
+testfs-OST0001
+testfs-OST0002
+
+Secure RPC Config Rules:
+
+imperative_recovery_state:
+ state: startup
+ nonir_clients: 0
+ nidtbl_version: 6
+ notify_duration_total: 0.001000
+ notify_duation_max: 0.001000
+ notify_count: 4</screen>
</listitem>
- </itemizedlist>
- <para>All servers are named according to this convention: <literal><replaceable>fsname</replaceable>-<replaceable>MDT|OSTnumber</replaceable></literal>. This can be shown for live servers under <literal>/proc/fs/lustre/devices</literal>:</para>
- <screen>mds# cat /proc/fs/lustre/devices
+ <listitem>
+ <para>To view the names of all live servers in the file system as listed in
+ <literal>/proc/fs/lustre/devices</literal>, enter:</para>
+ <screen># lctl device_list
0 UP mgs MGS MGS 11
1 UP mgc MGC192.168.10.34@tcp 1f45bb57-d9be-2ddb-c0b0-5431a49226705
2 UP mdt MDS MDS_uuid 3
-3 UP lov lustre-mdtlov lustre-mdtlov_UUID 4
-4 UP mds lustre-MDT0000 lustre-MDT0000_UUID 7
-5 UP osc lustre-OST0000-osc lustre-mdtlov_UUID 5
-6 UP osc lustre-OST0001-osc lustre-mdtlov_UUID 5
-7 UP lov lustre-clilov-ce63ca00 08ac6584-6c4a-3536-2c6d-b36cf9cbdaa04
-8 UP mdc lustre-MDT0000-mdc-ce63ca00 08ac6584-6c4a-3536-2c6d-b36cf9cbdaa05
-9 UP osc lustre-OST0000-osc-ce63ca00 08ac6584-6c4a-3536-2c6d-b36cf9cbdaa05
-10 UP osc lustre-OST0001-osc-ce63ca00 08ac6584-6c4a-3536-2c6d-b36cf9cbdaa05</screen>
- <para>Or from the device label at any time:</para>
- <screen>mds# e2label /dev/sda
-lustre-MDT0000</screen>
+3 UP lov testfs-mdtlov testfs-mdtlov_UUID 4
+4 UP mds testfs-MDT0000 testfs-MDT0000_UUID 7
+5 UP osc testfs-OST0000-osc testfs-mdtlov_UUID 5
+6 UP osc testfs-OST0001-osc testfs-mdtlov_UUID 5
+7 UP lov testfs-clilov-ce63ca00 08ac6584-6c4a-3536-2c6d-b36cf9cbdaa04
+8 UP mdc testfs-MDT0000-mdc-ce63ca00 08ac6584-6c4a-3536-2c6d-b36cf9cbdaa05
+9 UP osc testfs-OST0000-osc-ce63ca00 08ac6584-6c4a-3536-2c6d-b36cf9cbdaa05
+10 UP osc testfs-OST0001-osc-ce63ca00 08ac6584-6c4a-3536-2c6d-b36cf9cbdaa05</screen>
+ <para>The information provided on each line includes:</para>
+ <para> - Device number</para>
+ <para> - Device status (UP, INactive, or STopping) </para>
+ <para> - Device name</para>
+ <para> - Device UUID</para>
+ <para> - Reference count (how many users this device has)</para>
+ </listitem>
+ <listitem>
+ <para>To display the name of any server, view the device
+ label:<screen>mds# e2label /dev/sda
+testfs-MDT0000</screen></para>
+ </listitem>
+ </itemizedlist>
</section>
- <section remap="h3">
- <title><indexterm><primary>proc</primary><secondary>timeouts</secondary></indexterm>Lustre Timeouts</title>
- <para>Lustre uses two types of timeouts.</para>
+ </section>
+ <section>
+ <title>Tuning Multi-Block Allocation (mballoc)</title>
+ <para>Capabilities supported by <literal>mballoc</literal> include:</para>
+ <itemizedlist>
+ <listitem>
+ <para> Pre-allocation for single files to help to reduce fragmentation.</para>
+ </listitem>
+ <listitem>
+ <para> Pre-allocation for a group of files to enable packing of small files into large,
+ contiguous chunks.</para>
+ </listitem>
+ <listitem>
+ <para> Stream allocation to help decrease the seek rate.</para>
+ </listitem>
+ </itemizedlist>
+ <para>The following <literal>mballoc</literal> tunables are available:</para>
+ <informaltable frame="all">
+ <tgroup cols="2">
+ <colspec colname="c1" colwidth="30*"/>
+ <colspec colname="c2" colwidth="70*"/>
+ <thead>
+ <row>
+ <entry>
+ <para><emphasis role="bold">Field</emphasis></para>
+ </entry>
+ <entry>
+ <para><emphasis role="bold">Description</emphasis></para>
+ </entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>
+ <para>
+ <literal>mb_max_to_scan</literal></para>
+ </entry>
+ <entry>
+ <para>Maximum number of free chunks that <literal>mballoc</literal> finds before a
+ final decision to avoid a livelock situation.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal>mb_min_to_scan</literal></para>
+ </entry>
+ <entry>
+ <para>Minimum number of free chunks that <literal>mballoc</literal> searches before
+ picking the best chunk for allocation. This is useful for small requests to reduce
+ fragmentation of big free chunks.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal>mb_order2_req</literal></para>
+ </entry>
+ <entry>
+ <para>For requests equal to 2^N, where N >= <literal>mb_order2_req</literal>, a
+ fast search is done using a base 2 buddy allocation service.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal>mb_small_req</literal></para>
+ </entry>
+ <entry morerows="1">
+ <para><literal>mb_small_req</literal> - Defines (in MB) the upper bound of "small
+ requests".</para>
+ <para><literal>mb_large_req</literal> - Defines (in MB) the lower bound of "large
+ requests".</para>
+ <para>Requests are handled differently based on size:<itemizedlist>
+ <listitem>
+ <para>< <literal>mb_small_req</literal> - Requests are packed together to
+ form large, aggregated requests.</para>
+ </listitem>
+ <listitem>
+ <para>> <literal>mb_small_req</literal> and < <literal>mb_large_req</literal>
+ - Requests are primarily allocated linearly.</para>
+ </listitem>
+ <listitem>
+ <para>> <literal>mb_large_req</literal> - Requests are allocated since hard disk
+ seek time is less of a concern in this case.</para>
+ </listitem>
+ </itemizedlist></para>
+ <para>In general, small requests are combined to create larger requests, which are
+ then placed close to one another to minimize the number of seeks required to access
+ the data.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal>mb_large_req</literal></para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal>mb_prealloc_table</literal></para>
+ </entry>
+ <entry>
+ <para>A table of values used to preallocate space when a new request is received. By
+ default, the table looks like
+ this:<screen>prealloc_table
+4 8 16 32 64 128 256 512 1024 2048 </screen></para>
+ <para>When a new request is received, space is preallocated at the next higher
+ increment specified in the table. For example, for requests of less than 4 file
+ system blocks, 4 blocks of space are preallocated; for requests between 4 and 8, 8
+ blocks are preallocated; and so forth</para>
+ <para>Although customized values can be entered in the table, the performance of
+ general usage file systems will not typically be improved by modifying the table (in
+ fact, in ext4 systems, the table values are fixed). However, for some specialized
+ workloads, tuning the <literal>prealloc_table</literal> values may result in smarter
+ preallocation decisions. </para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal>mb_group_prealloc</literal></para>
+ </entry>
+ <entry>
+ <para>The amount of space (in kilobytes) preallocated for groups of small
+ requests.</para>
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ </section>
+ <section>
+ <title>Monitoring Lustre File System I/O</title>
+ <para>A number of system utilities are provided to enable collection of data related to I/O
+ activity in a Lustre file system. In general, the data collected describes:</para>
+ <itemizedlist>
+ <listitem>
+ <para> Data transfer rates and throughput of inputs and outputs external to the Lustre file
+ system, such as network requests or disk I/O operations performed</para>
+ </listitem>
+ <listitem>
+ <para> Data about the throughput or transfer rates of internal Lustre file system data, such
+ as locks or allocations. </para>
+ </listitem>
+ </itemizedlist>
+ <note>
+ <para>It is highly recommended that you complete baseline testing for your Lustre file system
+ to determine normal I/O activity for your hardware, network, and system workloads. Baseline
+ data will allow you to easily determine when performance becomes degraded in your system.
+ Two particularly useful baseline statistics are:</para>
<itemizedlist>
<listitem>
- <para>LND timeouts that ensure point-to-point communications complete in finite time in the presence of failures. These timeouts are logged with the <literal>S_LND</literal> flag set. They may <emphasis>not</emphasis> be printed as console messages, so you should check the Lustre log for <literal>D_NETERROR</literal> messages, or enable printing of <literal>D_NETERROR</literal> messages to the console (<literal>lctl set_param printk=+neterror</literal>).</para>
+ <para><literal>brw_stats</literal> – Histogram data characterizing I/O requests to the
+ OSTs. For more details, see <xref xmlns:xlink="http://www.w3.org/1999/xlink"
+ linkend="dbdoclet.50438271_55057"/>.</para>
+ </listitem>
+ <listitem>
+ <para><literal>rpc_stats</literal> – Histogram data showing information about RPCs made by
+ clients. For more details, see <xref xmlns:xlink="http://www.w3.org/1999/xlink"
+ linkend="MonitoringClientRCPStream"/>.</para>
</listitem>
</itemizedlist>
- <para>Congested routers can be a source of spurious LND timeouts. To avoid this, increase the number of LNET router buffers to reduce back-pressure and/or increase LND timeouts on all nodes on all connected networks. You should also consider increasing the total number of LNET router nodes in the system so that the aggregate router bandwidth matches the aggregate server bandwidth.</para>
+ </note>
+ <section remap="h3" xml:id="MonitoringClientRCPStream">
+ <title><indexterm>
+ <primary>proc</primary>
+ <secondary>watching RPC</secondary>
+ </indexterm>Monitoring the Client RPC Stream</title>
+ <para>The <literal>rpc_stats</literal> file contains histogram data showing information about
+ remote procedure calls (RPCs) that have been made since this file was last cleared. The
+ histogram data can be cleared by writing any value into the <literal>rpc_stats</literal>
+ file.</para>
+ <para><emphasis role="italic"><emphasis role="bold">Example:</emphasis></emphasis></para>
+ <screen># lctl get_param osc.testfs-OST0000-osc-ffff810058d2f800.rpc_stats
+snapshot_time: 1372786692.389858 (secs.usecs)
+read RPCs in flight: 0
+write RPCs in flight: 1
+dio read RPCs in flight: 0
+dio write RPCs in flight: 0
+pending write pages: 256
+pending read pages: 0
+
+ read write
+pages per rpc rpcs % cum % | rpcs % cum %
+1: 0 0 0 | 0 0 0
+2: 0 0 0 | 1 0 0
+4: 0 0 0 | 0 0 0
+8: 0 0 0 | 0 0 0
+16: 0 0 0 | 0 0 0
+32: 0 0 0 | 2 0 0
+64: 0 0 0 | 2 0 0
+128: 0 0 0 | 5 0 0
+256: 850 100 100 | 18346 99 100
+
+ read write
+rpcs in flight rpcs % cum % | rpcs % cum %
+0: 691 81 81 | 1740 9 9
+1: 48 5 86 | 938 5 14
+2: 29 3 90 | 1059 5 20
+3: 17 2 92 | 1052 5 26
+4: 13 1 93 | 920 5 31
+5: 12 1 95 | 425 2 33
+6: 10 1 96 | 389 2 35
+7: 30 3 100 | 11373 61 97
+8: 0 0 100 | 460 2 100
+
+ read write
+offset rpcs % cum % | rpcs % cum %
+0: 850 100 100 | 18347 99 99
+1: 0 0 100 | 0 0 99
+2: 0 0 100 | 0 0 99
+4: 0 0 100 | 0 0 99
+8: 0 0 100 | 0 0 99
+16: 0 0 100 | 1 0 99
+32: 0 0 100 | 1 0 99
+64: 0 0 100 | 3 0 99
+128: 0 0 100 | 4 0 100
+
+</screen>
+ <para>The header information includes:</para>
<itemizedlist>
<listitem>
- <para>Lustre timeouts that ensure Lustre RPCs complete in finite time in the presence of failures. These timeouts should <emphasis>always</emphasis> be printed as console messages. If Lustre timeouts are not accompanied by LNET timeouts, then you need to increase the lustre timeout on both servers and clients.</para>
+ <para><literal>snapshot_time</literal> - UNIX* epoch instant the file was read.</para>
+ </listitem>
+ <listitem>
+ <para><literal>read RPCs in flight</literal> - Number of read RPCs issued by the OSC, but
+ not complete at the time of the snapshot. This value should always be less than or equal
+ to <literal>max_rpcs_in_flight</literal>.</para>
+ </listitem>
+ <listitem>
+ <para><literal>write RPCs in flight</literal> - Number of write RPCs issued by the OSC,
+ but not complete at the time of the snapshot. This value should always be less than or
+ equal to <literal>max_rpcs_in_flight</literal>.</para>
+ </listitem>
+ <listitem>
+ <para><literal>dio read RPCs in flight</literal> - Direct I/O (as opposed to block I/O)
+ read RPCs issued but not completed at the time of the snapshot.</para>
+ </listitem>
+ <listitem>
+ <para><literal>dio write RPCs in flight</literal> - Direct I/O (as opposed to block I/O)
+ write RPCs issued but not completed at the time of the snapshot.</para>
+ </listitem>
+ <listitem>
+ <para><literal>pending write pages</literal> - Number of pending write pages that have
+ been queued for I/O in the OSC.</para>
+ </listitem>
+ <listitem>
+ <para><literal>pending read pages</literal> - Number of pending read pages that have been
+ queued for I/O in the OSC.</para>
</listitem>
</itemizedlist>
- <para>Specific Lustre timeouts are described below.</para>
- <para><literal> /proc/sys/lustre/timeout </literal></para>
- <para>This is the time period that a client waits for a server to complete an RPC (default is 100s). Servers wait half of this time for a normal client RPC to complete and a quarter of this time for a single bulk request (read or write of up to 4 MB) to complete. The client pings recoverable targets (MDS and OSTs) at one quarter of the timeout, and the server waits one and a half times the timeout before evicting a client for being "stale."</para>
- <note>
- <para>Lustre sends periodic 'PING' messages to servers with which it had no communication for a specified period of time. Any network activity on the file system that triggers network traffic toward servers also works as a health check.</para>
- </note>
- <para><literal> /proc/sys/lustre/ldlm_timeout </literal></para>
- <para>This is the time period for which a server will wait for a client to reply to an initial AST (lock cancellation request) where default is 20s for an OST and 6s for an MDS. If the client replies to the AST, the server will give it a normal timeout (half of the client timeout) to flush any dirty data and release the lock.</para>
- <para><literal> /proc/sys/lustre/fail_loc </literal></para>
- <para>This is the internal debugging failure hook.</para>
- <para>See <literal>lustre/include/linux/obd_support.h</literal> for the definitions of individual failure locations. The default value is 0 (zero).</para>
- <screen>sysctl -w lustre.fail_loc=0x80000122 # drop a single reply</screen>
- <para><literal> /proc/sys/lustre/dump_on_timeout </literal></para>
- <para>This triggers dumps of the Lustre debug log when timeouts occur. The default value is 0 (zero).</para>
- <para><literal> /proc/sys/lustre/dump_on_eviction </literal></para>
- <para>This triggers dumps of the Lustre debug log when an eviction occurs. The default value is 0 (zero). By default, debug logs are dumped to the /tmp folder; this location can be changed via /proc.</para>
- </section>
- <section remap="h3">
- <title><indexterm><primary>proc</primary><secondary>adaptive timeouts</secondary></indexterm>Adaptive Timeouts</title>
- <para>Lustre offers an adaptive mechanism to set RPC timeouts. The adaptive timeouts feature (enabled, by default) causes servers to track actual RPC completion times, and to report estimated completion times for future RPCs back to clients. The clients use these estimates to set their future RPC timeout values. If server request processing slows down for any reason, the RPC completion estimates increase, and the clients allow more time for RPC completion.</para>
- <para>If RPCs queued on the server approach their timeouts, then the server sends an early reply to the client, telling the client to allow more time. In this manner, clients avoid RPC timeouts and disconnect/reconnect cycles. Conversely, as a server speeds up, RPC timeout values decrease, allowing faster detection of non-responsive servers and faster attempts to reconnect to a server's failover partner.</para>
- <para>In previous Lustre versions, the static obd_timeout (<literal>/proc/sys/lustre/timeout</literal>) value was used as the maximum completion time for all RPCs; this value also affected the client-server ping interval and initial recovery timer. Now, with adaptive timeouts, obd_timeout is only used for the ping interval and initial recovery estimate. When a client reconnects during recovery, the server uses the client's timeout value to reset the recovery wait period; i.e., the server learns how long the client had been willing to wait, and takes this into account when adjusting the recovery period.</para>
- <section remap="h4">
- <title><indexterm><primary>proc</primary><secondary>configuring adaptive timeouts</secondary></indexterm><indexterm><primary>configuring</primary><secondary>adaptive timeouts</secondary></indexterm>Configuring Adaptive Timeouts</title>
- <para>One of the goals of adaptive timeouts is to relieve users from having to tune the <literal>obd_timeout</literal> value. In general, <literal>obd_timeout</literal> should no longer need to be changed. However, there are several parameters related to adaptive timeouts that users can set. In most situations, the default values should be used.</para>
- <para>The following parameters can be set persistently system-wide using <literal>lctl conf_param</literal> on the MGS. For example, <literal>lctl conf_param work1.sys.at_max=1500</literal> sets the at_max value for all servers and clients using the work1 file system.</para>
- <note>
- <para>Nodes using multiple Lustre file systems must use the same <literal>at_*</literal> values for all file systems.)</para>
- </note>
- <informaltable frame="all">
- <tgroup cols="2">
- <colspec colname="c1" colwidth="50*"/>
- <colspec colname="c2" colwidth="50*"/>
- <thead>
- <row>
- <entry>
- <para><emphasis role="bold">Parameter</emphasis></para>
- </entry>
- <entry>
- <para><emphasis role="bold">Description</emphasis></para>
- </entry>
- </row>
- </thead>
- <tbody>
- <row>
- <entry>
- <para> <literal> at_min </literal></para>
- </entry>
- <entry>
- <para>Sets the minimum adaptive timeout (in seconds). Default value is 0. The at_min parameter is the minimum processing time that a server will report. Clients base their timeouts on this value, but they do not use this value directly. If you experience cases in which, for unknown reasons, the adaptive timeout value is too short and clients time out their RPCs (usually due to temporary network outages), then you can increase the at_min value to compensate for this. Ideally, users should leave at_min set to its default.</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> at_max </literal></para>
- </entry>
- <entry>
- <para>Sets the maximum adaptive timeout (in seconds). The <literal>at_max</literal> parameter is an upper-limit on the service time estimate, and is used as a 'failsafe' in case of rogue/bad/buggy code that would lead to never-ending estimate increases. If at_max is reached, an RPC request is considered 'broken' and should time out.</para>
- <para>Setting at_max to 0 causes adaptive timeouts to be disabled and the old fixed-timeout method (<literal>obd_timeout</literal>) to be used.</para>
- <note>
- <para>It is possible that slow hardware might validly cause the service estimate to increase beyond the default value of at_max. In this case, you should increase at_max to the maximum time you are willing to wait for an RPC completion.</para>
- </note>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> at_history </literal></para>
- </entry>
- <entry>
- <para>Sets a time period (in seconds) within which adaptive timeouts remember the slowest event that occurred. Default value is 600.</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> at_early_margin </literal></para>
- </entry>
- <entry>
- <para>Sets how far before the deadline Lustre sends an early reply. Default value is 5<footnote>
- <para>This default was chosen as a reasonable time in which to send a reply from the point at which it was sent.</para>
- </footnote>.</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> at_extra </literal></para>
- </entry>
- <entry>
- <para>Sets the incremental amount of time that a server asks for, with each early reply. The server does not know how much time the RPC will take, so it asks for a fixed value. Default value is 30<footnote>
- <para>This default was chosen as a balance between sending too many early replies for the same RPC and overestimating the actual completion time</para>
- </footnote>. When a server finds a queued request about to time out (and needs to send an early reply out), the server adds the at_extra value. If the time expires, the Lustre client enters recovery status and reconnects to restore it to normal status.</para>
- <para>If you see multiple early replies for the same RPC asking for multiple 30-second increases, change the at_extra value to a larger number to cut down on early replies sent and, therefore, network load.</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> ldlm_enqueue_min </literal></para>
- </entry>
- <entry>
- <para> Sets the minimum lock enqueue time. Default value is 100. The <literal>ldlm_enqueue</literal> time is the maximum of the measured enqueue estimate (influenced by at_min and at_max parameters), multiplied by a weighting factor, and the <literal>ldlm_enqueue_min</literal> setting. LDLM lock enqueues were based on the <literal>obd_timeout</literal> value; now they have a dedicated minimum value. Lock enqueues increase as the measured enqueue times increase (similar to adaptive timeouts).</para>
- </entry>
- </row>
- </tbody>
- </tgroup>
- </informaltable>
- <para>Adaptive timeouts are enabled, by default. To disable adaptive timeouts, at run time, set <literal>at_max</literal> to 0. On the MGS, run:</para>
- <screen>$ lctl conf_param <replaceable>fsname</replaceable>.sys.at_max=0</screen>
- <note>
- <para>Changing adaptive timeouts status at runtime may cause transient timeout, reconnect, recovery, etc.</para>
- </note>
- </section>
- <section remap="h4">
- <title><indexterm><primary>proc</primary><secondary>interpreting adaptive timeouts</secondary></indexterm>Interpreting Adaptive Timeouts Information</title>
- <para>Adaptive timeouts information can be read from <literal>/proc/fs/lustre/*/timeouts</literal> files (for each service and client) or with the lctl command.</para>
- <para>This is an example from the <literal>/proc/fs/lustre/*/timeouts</literal> files:</para>
- <screen>cfs21:~# cat /proc/fs/lustre/ost/OSS/ost_io/timeouts</screen>
- <para>This is an example using the <literal>lctl</literal> command:</para>
- <screen>$ lctl get_param -n ost.*.ost_io.timeouts</screen>
- <para>This is the sample output:</para>
- <screen>service : cur 33 worst 34 (at 1193427052, 0d0h26m40s ago) 1 1 33 2</screen>
- <para>The <literal>ost_io</literal> service on this node is currently reporting an estimate of 33 seconds. The worst RPC service time was 34 seconds, and it happened 26 minutes ago.</para>
- <para>The output also provides a history of service times. In the example, there are 4 "bins" of <literal>adaptive_timeout_history</literal>, with the maximum RPC time in each bin reported. In 0-150 seconds, the maximum RPC time was 1, with the same result in 150-300 seconds. From 300-450 seconds, the worst (maximum) RPC time was 33 seconds, and from 450-600s the worst time was 2 seconds. The current estimated service time is the maximum value of the 4 bins (33 seconds in this example).</para>
- <para>Service times (as reported by the servers) are also tracked in the client OBDs:</para>
- <screen>cfs21:# lctl get_param osc.*.timeouts
-last reply : 1193428639, 0d0h00m00s ago
-network : cur 1 worst 2 (at 1193427053, 0d0h26m26s ago) 1 1 1 1
-portal 6 : cur 33 worst 34 (at 1193427052, 0d0h26m27s ago) 33 33 33 2
-portal 28 : cur 1 worst 1 (at 1193426141, 0d0h41m38s ago) 1 1 1 1
-portal 7 : cur 1 worst 1 (at 1193426141, 0d0h41m38s ago) 1 0 1 1
-portal 17 : cur 1 worst 1 (at 1193426177, 0d0h41m02s ago) 1 0 0 1
-</screen>
- <para>In this case, RPCs to portal 6, the <literal>OST_IO_PORTAL</literal> (see <literal>lustre/include/lustre/lustre_idl.h</literal>), shows the history of what the <literal>ost_io</literal> portal has reported as the service estimate.</para>
- <para>Server statistic files also show the range of estimates in the normal min/max/sum/sumsq manner.</para>
- <screen>cfs21:~# lctl get_param mdt.*.mdt.stats
-...
-req_timeout 6 samples [sec] 1 10 15 105
-...
-</screen>
- </section>
- </section>
- <section remap="h3">
- <title><indexterm><primary>proc</primary><secondary>LNET</secondary></indexterm><indexterm><primary>LNET</primary><secondary>proc</secondary></indexterm>LNET Information</title>
- <para>This section describes<literal> /proc</literal> entries for LNET information.</para>
- <para><literal> /proc/sys/lnet/peers </literal></para>
- <para>Shows all NIDs known to this node and also gives information on the queue state.</para>
- <screen># cat /proc/sys/lnet/peers
-nid refs state max rtr min tx min queue
-0@lo 1 ~rtr 0 0 0 0 0 0
-192.168.10.35@tcp 1 ~rtr 8 8 8 8 6 0
-192.168.10.36@tcp 1 ~rtr 8 8 8 8 6 0
-192.168.10.37@tcp 1 ~rtr 8 8 8 8 6 0</screen>
- <para>The fields are explained below:</para>
+ <para>The tabular data is described in the table below. Each row in the table shows the number
+ of reads or writes (<literal>ios</literal>) occurring for the statistic, the relative
+ percentage (<literal>%</literal>) of total reads or writes, and the cumulative percentage
+ (<literal>cum %</literal>) to that point in the table for the statistic.</para>
<informaltable frame="all">
<tgroup cols="2">
- <colspec colname="c1" colwidth="50*"/>
- <colspec colname="c2" colwidth="50*"/>
+ <colspec colname="c1" colwidth="40*"/>
+ <colspec colname="c2" colwidth="60*"/>
<thead>
<row>
<entry>
<tbody>
<row>
<entry>
- <para>
- <literal>
- <replaceable>refs</replaceable>
- </literal>
- </para>
- </entry>
- <entry>
- <para>A reference count (principally used for debugging)</para>
- </entry>
- </row>
- <row>
- <entry>
- <para>
- <literal>
- <replaceable>state</replaceable>
- </literal>
- </para>
- </entry>
- <entry>
- <para>Only valid to refer to routers. Possible values:</para>
- <itemizedlist>
- <listitem>
- <para>~ rtr (indicates this node is not a router)</para>
- </listitem>
- <listitem>
- <para>up/down (indicates this node is a router)</para>
- </listitem>
- <listitem>
- <para>auto_fail must be enabled</para>
- </listitem>
- </itemizedlist>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> max </literal></para>
- </entry>
- <entry>
- <para>Maximum number of concurrent sends from this peer</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> rtr </literal></para>
- </entry>
- <entry>
- <para>Routing buffer credits.</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> min </literal></para>
- </entry>
- <entry>
- <para>Minimum routing buffer credits seen.</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> tx </literal></para>
+ <para> pages per RPC</para>
</entry>
<entry>
- <para>Send credits.</para>
+ <para>Shows cumulative RPC reads and writes organized according to the number of
+ pages in the RPC. A single page RPC increments the <literal>0:</literal>
+ row.</para>
</entry>
</row>
<row>
<entry>
- <para> <literal> min </literal></para>
+ <para> RPCs in flight</para>
</entry>
<entry>
- <para>Minimum send credits seen.</para>
+ <para> Shows the number of RPCs that are pending when an RPC is sent. When the first
+ RPC is sent, the <literal>0:</literal> row is incremented. If the first RPC is
+ sent while another RPC is pending, the <literal>1:</literal> row is incremented
+ and so on. </para>
</entry>
</row>
<row>
<entry>
- <para> <literal> queue </literal></para>
+ <para> offset</para>
</entry>
<entry>
- <para>Total bytes in active/queued sends.</para>
+ <para> The page index of the first page read from or written to the object by the
+ RPC. </para>
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
- <para>Credits work like a semaphore. At start they are initialized to allow a certain number of operations (8 in this example). LNET keeps a track of the minimum value so that you can see how congested a resource was.</para>
- <para>If <literal>rtr/tx</literal> is less than max, there are operations in progress. The number of operations is equal to <literal>rtr</literal> or <literal>tx</literal> subtracted from max.</para>
- <para>If <literal>rtr/tx</literal> is greater that max, there are operations blocking.</para>
- <para>LNET also limits concurrent sends and router buffers allocated to a single peer so that no peer can occupy all these resources.</para>
- <para><literal> /proc/sys/lnet/nis </literal></para>
- <screen># cat /proc/sys/lnet/nis
-nid refs peer max tx min
-0@lo 3 0 0 0 0
-192.168.10.34@tcp 4 8 256 256 252
-</screen>
- <para>Shows the current queue health on this node. The fields are explained below:</para>
+ <para><emphasis role="italic"><emphasis role="bold">Analysis:</emphasis></emphasis></para>
+ <para>This table provides a way to visualize the concurrency of the RPC stream. Ideally, you
+ will see a large clump around the <literal>max_rpcs_in_flight value</literal>, which shows
+ that the network is being kept busy.</para>
+ <para>For information about optimizing the client I/O RPC stream, see <xref
+ xmlns:xlink="http://www.w3.org/1999/xlink" linkend="TuningClientIORPCStream"/>.</para>
+ </section>
+ <section remap="h3">
+ <title><indexterm>
+ <primary>proc</primary>
+ <secondary>read/write survey</secondary>
+ </indexterm>Monitoring Client Read-Write Offset Statistics</title>
+ <para>The <literal>offset_stats</literal> parameter maintains statistics for occurrences of a
+ series of read or write calls from a process that did not access the next sequential
+ location. The <literal>OFFSET</literal> field is reset to 0 (zero) whenever a different file
+ is read or written.</para>
+ <para>Read/write offset statistics are "off" by default. The statistics can be activated by
+ writing anything into the <literal>offset_stats</literal> file.</para>
+ <para>The <literal>offset_stats</literal> file can be cleared by
+ entering:<screen>lctl set_param llite.*.offset_stats=0</screen></para>
+ <para><emphasis role="italic"><emphasis role="bold">Example:</emphasis></emphasis></para>
+ <screen># lctl get_param llite.testfs-f57dee0.offset_stats
+snapshot_time: 1155748884.591028 (secs.usecs)
+ RANGE RANGE SMALLEST LARGEST
+R/W PID START END EXTENT EXTENT OFFSET
+R 8385 0 128 128 128 0
+R 8385 0 224 224 224 -128
+W 8385 0 250 50 100 0
+W 8385 100 1110 10 500 -150
+W 8384 0 5233 5233 5233 0
+R 8385 500 600 100 100 -610</screen>
+ <para>In this example, <literal>snapshot_time</literal> is the UNIX epoch instant the file was
+ read. The tabular data is described in the table below.</para>
<informaltable frame="all">
<tgroup cols="2">
<colspec colname="c1" colwidth="50*"/>
<tbody>
<row>
<entry>
- <para> <literal> nid </literal></para>
- </entry>
- <entry>
- <para>Network interface</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> refs </literal></para>
+ <para>R/W</para>
</entry>
<entry>
- <para>Internal reference counter</para>
+ <para>Indicates if the non-sequential call was a read or write</para>
</entry>
</row>
<row>
<entry>
- <para> <literal> peer </literal></para>
+ <para>PID </para>
</entry>
<entry>
- <para>Number of peer-to-peer send credits on this NID. Credits are used to size buffer pools</para>
+ <para>Process ID of the process that made the read/write call.</para>
</entry>
</row>
<row>
<entry>
- <para> <literal> max </literal></para>
+ <para>RANGE START/RANGE END</para>
</entry>
<entry>
- <para>Total number of send credits on this NID.</para>
+ <para>Range in which the read/write calls were sequential.</para>
</entry>
</row>
<row>
<entry>
- <para> <literal> tx </literal></para>
+ <para>SMALLEST EXTENT </para>
</entry>
<entry>
- <para>Current number of send credits available on this NID.</para>
+ <para>Smallest single read/write in the corresponding range (in bytes).</para>
</entry>
</row>
<row>
<entry>
- <para> <literal> min </literal></para>
+ <para>LARGEST EXTENT </para>
</entry>
<entry>
- <para>Lowest number of send credits available on this NID.</para>
+ <para>Largest single read/write in the corresponding range (in bytes).</para>
</entry>
</row>
<row>
<entry>
- <para> <literal> queue </literal></para>
+ <para>OFFSET </para>
</entry>
<entry>
- <para>Total bytes in active/queued sends.</para>
+ <para>Difference between the previous range end and the current range start.</para>
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
- <para>Subtracting <literal>max</literal> - <literal>tx</literal> yields the number of sends currently active. A large or increasing number of active sends may indicate a problem.</para>
- <screen># cat /proc/sys/lnet/nis
-nid refs peer max tx min
-0@lo 2 0 0 0 0
-10.67.73.173@tcp 4 8 256 256 253
-</screen>
+ <para><emphasis role="italic"><emphasis role="bold">Analysis:</emphasis></emphasis></para>
+ <para>This data provides an indication of how contiguous or fragmented the data is. For
+ example, the fourth entry in the example above shows the writes for this RPC were sequential
+ in the range 100 to 1110 with the minimum write 10 bytes and the maximum write 500 bytes.
+ The range started with an offset of -150 from the <literal>RANGE END</literal> of the
+ previous entry in the example.</para>
</section>
- <section remap="h3">
+ <section xml:id="lustreproc.clientstats" remap="h3">
<title><indexterm>
<primary>proc</primary>
- <secondary>free space distribution</secondary>
- </indexterm>Free Space Distribution</title>
- <para>Free space is allocated using either a round-robin or a weighted algorithm. The
- allocation method is determined by the amount of free-space imbalance on the OSTs. When free
- space is relatively balanced across OSTs, the faster round-robin allocator is used, which
- maximizes network balancing. The weighted allocator is used when any two OSTs are out of
- balance by more than a specified threshold.</para>
- <para>Free space distribution can be tuned using these two <literal>/proc</literal>
- tunables:</para>
- <itemizedlist>
- <listitem>
- <para><literal>qos_threshold_rr</literal> - The threshold at which the allocation method
- switches from round-robin to weighted is set in this file. The default is to switch to
- the weighted algorithm when any two OSTs are out of balance by more than 17
- percent.</para>
- </listitem>
- <listitem>
- <para><literal>qos_prio_free</literal> - The weighting priority used by the weighted
- allocator can be adjusted in this file. Increasing the value of
- <literal>qos_prio_free</literal> puts more weighting on the amount of free space
- available on each OST and less on how stripes are distributed across OSTs. The default
- value is 91 percent. When the free space priority is set to 100, weighting is based
- entirely on free space and location is no longer used by the striping algorthm.</para>
- </listitem>
- </itemizedlist>
- <para>For more information about managing free space and setting <literal>/proc</literal>
- tunables, see <xref xmlns:xlink="http://www.w3.org/1999/xlink"
- linkend="dbdoclet.50438209_10424"/>.</para>
- </section>
- </section>
- <section xml:id="dbdoclet.50438271_78950">
- <title><indexterm><primary>proc</primary><secondary>I/O tunables</secondary></indexterm>Lustre I/O Tunables</title>
- <para>The section describes I/O tunables.</para>
- <para><literal> llite.<replaceable>fsname-instance</replaceable>/max_cache_mb</literal></para>
- <screen>client# lctl get_param llite.lustre-ce63ca00.max_cached_mb
-128</screen>
- <para>This tunable is the maximum amount of inactive data cached by the client (default is 3/4 of RAM).</para>
- <section remap="h3">
- <title><indexterm><primary>proc</primary><secondary>RPC tunables</secondary></indexterm>Client I/O RPC Stream Tunables</title>
- <para>The Lustre engine always attempts to pack an optimal amount of data into each I/O RPC and attempts to keep a consistent number of issued RPCs in progress at a time. Lustre exposes several tuning variables to adjust behavior according to network conditions and cluster size. Each OSC has its own tree of these tunables. For example:</para>
- <screen>$ ls -d /proc/fs/lustre/osc/OSC_client_ost1_MNT_client_2 /localhost
-/proc/fs/lustre/osc/OSC_uml0_ost1_MNT_localhost
-/proc/fs/lustre/osc/OSC_uml0_ost2_MNT_localhost
-/proc/fs/lustre/osc/OSC_uml0_ost3_MNT_localhost
-$ ls /proc/fs/lustre/osc/OSC_uml0_ost1_MNT_localhost
-blocksizefilesfree max_dirty_mb ost_server_uuid stats</screen>
- <para>... and so on.</para>
- <para>RPC stream tunables are described below.</para>
- <para><literal> osc.<replaceable>osc_instance</replaceable>.max_dirty_mb </literal></para>
- <para xml:id='lustreproc.maxdirtymb'>This tunable controls how many MBs of dirty data can be written and queued up in the OSC. POSIX file writes that are cached contribute to this count. When the limit is reached, additional writes stall until previously-cached writes are written to the server. This may be changed by writing a single ASCII integer to the file. Only values between 0 and 2048 or 1/4 of RAM are allowable. If 0 is given, no writes are cached. Performance suffers noticeably unless you use large writes (1 MB or more).</para>
- <para><literal> osc.<replaceable>osc_instance</replaceable>.cur_dirty_bytes </literal></para>
- <para>This tunable is a read-only value that returns the current amount of bytes written and cached on this OSC.</para>
- <para><literal> osc.<replaceable>osc_instance</replaceable>.max_pages_per_rpc </literal></para>
- <para>This tunable is the maximum number of pages that will undergo I/O in a single RPC to the OST. The minimum is a single page and the maximum for this setting is 1024 (for systems with 4kB <literal>PAGE_SIZE</literal>), with the default maximum of 1MB in the RPC. It is also possible to specify a units suffix (e.g. <literal>4M</literal>), so that the RPC size can be specified independently of the client <literal>PAGE_SIZE</literal>.</para>
- <para><literal> osc.<replaceable>osc_instance</replaceable>.max_rpcs_in_flight </literal></para>
- <para>This tunable is the maximum number of concurrent RPCs in flight from an OSC to its OST. If the OSC tries to initiate an RPC but finds that it already has the same number of RPCs outstanding, it will wait to issue further RPCs until some complete. The minimum setting is 1 and maximum setting is 256. If you are looking to improve small file I/O performance, increase the <literal>max_rpcs_in_flight</literal> value.</para>
- <para>To maximize performance, the value for <literal>max_dirty_mb</literal> is recommended to be 4 * <literal>max_pages_per_rpc</literal> * <literal>max_rpcs_in_flight</literal>.</para>
+ <secondary>client stats</secondary>
+ </indexterm>Monitoring Client Activity</title>
+ <para>The <literal>stats</literal> file maintains statistics accumulate during typical
+ operation of a client across the VFS interface of the Lustre file system. Only non-zero
+ parameters are displayed in the file. </para>
+ <para>Client statistics are enabled by default. The statistics can be cleared by echoing an
+ empty string into the <literal>stats</literal> file or by using the command:
+ <screen>lctl set_param llite.*.stats=0</screen></para>
<note>
- <para>The
- <literal>
- <replaceable>osc_instance</replaceable>
- </literal>
- is typically <literal><replaceable>fsname</replaceable>-OST<replaceable>ost_index</replaceable>-osc-<replaceable>mountpoint_instance</replaceable></literal>. The <literal><replaceable>mountpoint_instance</replaceable></literal> is a unique value per mountpoint to allow associating osc, mdc, lov, lmv, and llite parameters for the same mountpoint. For <literal><replaceable>osc_instance</replaceable></literal> examples, refer to the sample command output.</para>
+ <para>Statistics for all mounted file systems can be discovered by
+ entering:<screen>lctl get_param llite.*.stats</screen></para>
</note>
- </section>
- <section remap="h3">
- <title><indexterm><primary>proc</primary><secondary>watching RPC</secondary></indexterm>Watching the Client RPC Stream</title>
- <para>The same directory contains a <literal>rpc_stats</literal> file with a histogram showing the composition of previous RPCs. The histogram can be cleared by writing any value into the <literal>rpc_stats</literal> file.</para>
- <screen># cat /proc/fs/lustre/osc/spfs-OST0000-osc-c45f9c00/rpc_stats
-snapshot_time: 1174867307.156604 (secs.usecs)
-read RPCs in flight: 0
-write RPCs in flight: 0
-pending write pages: 0
-pending read pages: 0
- read write
-pages per rpc rpcs % cum % | rpcs % cum %
-1: 0 0 0 | 0 0 0
-
- read write
-rpcs in flight rpcs % cum % | rpcs % cum %
-0: 0 0 0 | 0 0 0
-
- read write
-offset rpcs % cum % | rpcs % cum %
-0: 0 0 0 | 0 0 0
+ <para><emphasis role="italic"><emphasis role="bold">Example:</emphasis></emphasis></para>
+ <screen>client# lctl get_param llite.*.stats
+snapshot_time 1308343279.169704 secs.usecs
+dirty_pages_hits 14819716 samples [regs]
+dirty_pages_misses 81473472 samples [regs]
+read_bytes 36502963 samples [bytes] 1 26843582 55488794
+write_bytes 22985001 samples [bytes] 0 125912 3379002
+brw_read 2279 samples [pages] 1 1 2270
+ioctl 186749 samples [regs]
+open 3304805 samples [regs]
+close 3331323 samples [regs]
+seek 48222475 samples [regs]
+fsync 963 samples [regs]
+truncate 9073 samples [regs]
+setxattr 19059 samples [regs]
+getxattr 61169 samples [regs]
</screen>
- <para>Where:</para>
+ <para>The statistics displayed are described in the table below.</para>
<informaltable frame="all">
<tgroup cols="2">
- <colspec colname="c1" colwidth="50*"/>
- <colspec colname="c2" colwidth="50*"/>
+ <colspec colname="c1" colwidth="3*"/>
+ <colspec colname="c2" colwidth="7*"/>
<thead>
<row>
<entry>
- <para><emphasis role="bold">Field</emphasis></para>
+ <para><emphasis role="bold">Entry</emphasis></para>
</entry>
<entry>
<para><emphasis role="bold">Description</emphasis></para>
<tbody>
<row>
<entry>
- <para> <emphasis role="bold">{read,write} RPCs in flight</emphasis></para>
+ <para>
+ <literal>snapshot_time</literal></para>
</entry>
<entry>
- <para>Number of read/write RPCs issued by the OSC, but not complete at the time of the snapshot. This value should always be less than or equal to max_rpcs_in_flight.</para>
+ <para>UNIX epoch instant the stats file was read.</para>
</entry>
</row>
<row>
<entry>
- <para> <emphasis role="bold">pending {read,write} pages</emphasis></para>
+ <para>
+ <literal>dirty_page_hits</literal></para>
</entry>
<entry>
- <para>Number of pending read/write pages that have been queued for I/O in the OSC.</para>
+ <para>The number of write operations that have been satisfied by the dirty page
+ cache. See <xref xmlns:xlink="http://www.w3.org/1999/xlink"
+ linkend="TuningClientIORPCStream"/> for more information about dirty cache
+ behavior in a Lustre file system.</para>
</entry>
</row>
<row>
<entry>
- <para> <emphasis role="bold">pages per RPC</emphasis></para>
+ <para>
+ <literal>dirty_page_misses</literal></para>
</entry>
<entry>
- <para>When an RPC is sent, the number of pages it consists of is recorded (in order). A single page RPC increments the 0: row.</para>
+ <para>The number of write operations that were not satisfied by the dirty page
+ cache.</para>
</entry>
</row>
<row>
<entry>
- <para> <emphasis role="bold">RPCs in flight</emphasis></para>
+ <para>
+ <literal>read_bytes</literal></para>
</entry>
<entry>
- <para>When an RPC is sent, the number of other RPCs that are pending is recorded. When the first RPC is sent, the 0: row is incremented. If the first RPC is sent while another is pending, the 1: row is incremented and so on. As each RPC *completes*, the number of pending RPCs is not tabulated.</para>
- <para>This table is a good way to visualize the concurrency of the RPC stream. Ideally, you will see a large clump around the max_rpcs_in_flight value, which shows that the network is being kept busy.</para>
+ <para>The number of read operations that have occurred. Three additional parameters
+ are displayed:</para>
+ <variablelist>
+ <varlistentry>
+ <term>min</term>
+ <listitem>
+ <para>The minimum number of bytes read in a single request since the counter
+ was reset.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>max</term>
+ <listitem>
+ <para>The maximum number of bytes read in a single request since the counter
+ was reset.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>sum</term>
+ <listitem>
+ <para>The accumulated sum of bytes of all read requests since the counter was
+ reset.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
</entry>
</row>
<row>
<entry>
- <para> <emphasis role="bold">offset</emphasis></para>
+ <para>
+ <literal>write_bytes</literal></para>
</entry>
<entry>
- <para> </para>
+ <para>The number of write operations that have occurred. Three additional parameters
+ are displayed:</para>
+ <variablelist>
+ <varlistentry>
+ <term>min</term>
+ <listitem>
+ <para>The minimum number of bytes written in a single request since the
+ counter was reset.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>max</term>
+ <listitem>
+ <para>The maximum number of bytes written in a single request since the
+ counter was reset.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>sum</term>
+ <listitem>
+ <para>The accumulated sum of bytes of all write requests since the counter was
+ reset.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
</entry>
</row>
- </tbody>
- </tgroup>
- </informaltable>
- </section>
- <section remap="h3">
- <title><indexterm><primary>proc</primary><secondary>read/write survey</secondary></indexterm>Client Read-Write Offset Survey</title>
- <para>The offset_stats parameter maintains statistics for occurrences where a series of read or write calls from a process did not access the next sequential location. The offset field is reset to 0 (zero) whenever a different file is read/written.</para>
- <para>Read/write offset statistics are off, by default. The statistics can be activated by writing anything into the <literal>offset_stats</literal> file.</para>
- <para>Example:</para>
- <screen># cat /proc/fs/lustre/llite/lustre-f57dee00/rw_offset_stats
-snapshot_time: 1155748884.591028 (secs.usecs)
-R/W PID RANGE START RANGE END SMALLEST EXTENT LARGEST EXTENT OFFSET
-R 8385 0 128 128 128 0
-R 8385 0 224 224 224 -128
-W 8385 0 250 50 100 0
-W 8385 100 1110 10 500 -150
-W 8384 0 5233 5233 5233 0
-R 8385 500 600 100 100 -610</screen>
- <para>Where:</para>
- <informaltable frame="all">
- <tgroup cols="2">
- <colspec colname="c1" colwidth="50*"/>
- <colspec colname="c2" colwidth="50*"/>
- <thead>
<row>
<entry>
- <para><emphasis role="bold">Field</emphasis></para>
+ <para>
+ <literal>brw_read</literal></para>
</entry>
<entry>
- <para><emphasis role="bold">Description</emphasis></para>
+ <para>The number of pages that have been read. Three additional parameters are
+ displayed:</para>
+ <variablelist>
+ <varlistentry>
+ <term>min</term>
+ <listitem>
+ <para>The minimum number of bytes read in a single block read/write
+ (<literal>brw</literal>) read request since the counter was reset.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>max</term>
+ <listitem>
+ <para>The maximum number of bytes read in a single <literal>brw</literal> read
+ requests since the counter was reset.</para>
+ </listitem>
+ </varlistentry>
+ <varlistentry>
+ <term>sum</term>
+ <listitem>
+ <para>The accumulated sum of bytes of all <literal>brw</literal> read requests
+ since the counter was reset.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
</entry>
</row>
- </thead>
- <tbody>
<row>
<entry>
- <para> <literal> R/W </literal></para>
+ <para>
+ <literal>ioctl</literal></para>
</entry>
<entry>
- <para>Whether the non-sequential call was a read or write</para>
+ <para>The number of combined file and directory <literal>ioctl</literal>
+ operations.</para>
</entry>
</row>
<row>
<entry>
- <para> <literal> PID </literal></para>
+ <para>
+ <literal>open</literal></para>
</entry>
<entry>
- <para>Process ID which made the read/write call.</para>
+ <para>The number of open operations that have succeeded.</para>
</entry>
</row>
<row>
<entry>
- <para> <literal> Range Start/Range End </literal></para>
+ <para>
+ <literal>close</literal></para>
</entry>
<entry>
- <para>Range in which the read/write calls were sequential.</para>
+ <para>The number of close operations that have succeeded.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal>seek</literal></para>
+ </entry>
+ <entry>
+ <para>The number of times <literal>seek</literal> has been called.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal>fsync</literal></para>
+ </entry>
+ <entry>
+ <para>The number of times <literal>fsync</literal> has been called.</para>
</entry>
</row>
<row>
<entry>
- <para> <literal> Smallest Extent </literal></para>
+ <para>
+ <literal>truncate</literal></para>
</entry>
<entry>
- <para>Smallest extent (single read/write) in the corresponding range.</para>
+ <para>The total number of calls to both locked and lockless
+ <literal>truncate</literal>.</para>
</entry>
</row>
<row>
<entry>
- <para> <literal> Largest Extent </literal></para>
+ <para>
+ <literal>setxattr</literal></para>
</entry>
<entry>
- <para>Largest extent (single read/write) in the corresponding range.</para>
+ <para>The number of times extended attributes have been set. </para>
</entry>
</row>
<row>
<entry>
- <para> <literal> Offset </literal></para>
+ <para>
+ <literal>getxattr</literal></para>
</entry>
<entry>
- <para>Difference from the previous range end to the current range start.</para>
- <para>For example, Smallest-Extent indicates that the writes in the range 100 to 1110 were sequential, with a minimum write of 10 and a maximum write of 500. This range was started with an offset of -150. That means this is the difference between the last entry's range-end and this entry's range-start for the same file.</para>
- <para>The <literal>rw_offset_stats</literal> file can be cleared by writing to it:</para>
- <screen>lctl set_param llite.*.rw_offset_stats=0</screen>
+ <para>The number of times value(s) of extended attributes have been fetched.</para>
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
+ <para><emphasis role="italic"><emphasis role="bold">Analysis:</emphasis></emphasis></para>
+ <para>Information is provided about the amount and type of I/O activity is taking place on the
+ client.</para>
</section>
- <section xml:id="lustreproc.clientstats" remap="h3">
- <title><indexterm><primary>proc</primary><secondary>client stats</secondary></indexterm>Client stats</title>
- <para>The stats parameter maintains statistics of activity across the VFS interface of the Lustre file system. Only non-zero parameters are displayed in the file. This section of the manual covers the statistics that will accumulate during typical operation of a client.</para>
- <para>Client statistics are enabled by default. The statistics can be cleared by echoing an empty string into the <literal>stats</literal> file or with the command: <literal>lctl set_param llite.*.stats=0</literal>. Statistics for an individual file system can be displayed, for example:</para>
- <screen>client# lctl get_param llite.*.stats
-snapshot_time 1308343279.169704 secs.usecs
-dirty_pages_hits 14819716 samples [regs]
-dirty_pages_misses 81473472 samples [regs]
-read_bytes 36502963 samples [bytes] 1 26843582 55488794
-write_bytes 22985001 samples [bytes] 0 125912 3379002
-brw_read 2279 samples [pages] 1 1 2270
-ioctl 186749 samples [regs]
-open 3304805 samples [regs]
-close 3331323 samples [regs]
-seek 48222475 samples [regs]
-fsync 963 samples [regs]
-truncate 9073 samples [regs]
-setxattr 19059 samples [regs]
-getxattr 61169 samples [regs]
+ <section remap="h3">
+ <title><indexterm>
+ <primary>proc</primary>
+ <secondary>read/write survey</secondary>
+ </indexterm>Monitoring Client Read-Write Extent Statistics</title>
+ <para>For in-depth troubleshooting, client read-write extent statistics can be accessed to
+ obtain more detail about read/write I/O extents for the file system or for a particular
+ process.</para>
+ <section remap="h3">
+ <title>Client-Based I/O Extent Size Survey</title>
+ <para>The <literal>rw_extent_stats</literal> histogram in the <literal>llite</literal>
+ directory shows the statistics for the sizes of the read?write I/O extents. This file does
+ not maintain the per-process statistics. The file can be cleared by issuing the following
+ command:<screen># lctl set_param llite.testfs-*.extents_stats=0</screen></para>
+ <para><emphasis role="italic"><emphasis role="bold">Example:</emphasis></emphasis></para>
+ <screen># lctl get_param llite.testfs-*.extents_stats
+snapshot_time: 1213828728.348516 (secs.usecs)
+ read | write
+extents calls % cum% | calls % cum%
+
+0K - 4K : 0 0 0 | 2 2 2
+4K - 8K : 0 0 0 | 0 0 2
+8K - 16K : 0 0 0 | 0 0 2
+16K - 32K : 0 0 0 | 20 23 26
+32K - 64K : 0 0 0 | 0 0 26
+64K - 128K : 0 0 0 | 51 60 86
+128K - 256K : 0 0 0 | 0 0 86
+256K - 512K : 0 0 0 | 0 0 86
+512K - 1024K : 0 0 0 | 0 0 86
+1M - 2M : 0 0 0 | 11 13 100</screen>
+ <para>In this example, <literal>snapshot_time</literal> is the UNIX epoch instant the file
+ was read. The table shows cumulative extents organized according to size with statistics
+ provided separately for reads and writes. Each row in the table shows the number of RPCs
+ for reads and writes respectively (<literal>calls</literal>), the relative percentage of
+ total calls (<literal>%</literal>), and the cumulative percentage to that point in the
+ table of calls (<literal>cum %</literal>). </para>
+ </section>
+ <section>
+ <title>Per-Process Client I/O Statistics</title>
+ <para>The <literal>extents_stats_per_process</literal> file maintains the I/O extent size
+ statistics on a per-process basis.</para>
+ <para><emphasis role="italic"><emphasis role="bold">Example:</emphasis></emphasis></para>
+ <screen># lctl get_param llite.testfs-*.extents_stats_per_process
+snapshot_time: 1213828762.204440 (secs.usecs)
+ read | write
+extents calls % cum% | calls % cum%
+
+PID: 11488
+ 0K - 4K : 0 0 0 | 0 0 0
+ 4K - 8K : 0 0 0 | 0 0 0
+ 8K - 16K : 0 0 0 | 0 0 0
+ 16K - 32K : 0 0 0 | 0 0 0
+ 32K - 64K : 0 0 0 | 0 0 0
+ 64K - 128K : 0 0 0 | 0 0 0
+ 128K - 256K : 0 0 0 | 0 0 0
+ 256K - 512K : 0 0 0 | 0 0 0
+ 512K - 1024K : 0 0 0 | 0 0 0
+ 1M - 2M : 0 0 0 | 10 100 100
+
+PID: 11491
+ 0K - 4K : 0 0 0 | 0 0 0
+ 4K - 8K : 0 0 0 | 0 0 0
+ 8K - 16K : 0 0 0 | 0 0 0
+ 16K - 32K : 0 0 0 | 20 100 100
+
+PID: 11424
+ 0K - 4K : 0 0 0 | 0 0 0
+ 4K - 8K : 0 0 0 | 0 0 0
+ 8K - 16K : 0 0 0 | 0 0 0
+ 16K - 32K : 0 0 0 | 0 0 0
+ 32K - 64K : 0 0 0 | 0 0 0
+ 64K - 128K : 0 0 0 | 16 100 100
+
+PID: 11426
+ 0K - 4K : 0 0 0 | 1 100 100
+
+PID: 11429
+ 0K - 4K : 0 0 0 | 1 100 100
+
+</screen>
+ <para>This table shows cumulative extents organized according to size for each process ID
+ (PID) with statistics provided separately for reads and writes. Each row in the table
+ shows the number of RPCs for reads and writes respectively (<literal>calls</literal>), the
+ relative percentage of total calls (<literal>%</literal>), and the cumulative percentage
+ to that point in the table of calls (<literal>cum %</literal>). </para>
+ </section>
+ </section>
+ <section xml:id="dbdoclet.50438271_55057">
+ <title><indexterm>
+ <primary>proc</primary>
+ <secondary>block I/O</secondary>
+ </indexterm>Monitoring the OST Block I/O Stream</title>
+ <para>The <literal>brw_stats</literal> file in the <literal>obdfilter</literal> directory
+ contains histogram data showing statistics for number of I/O requests sent to the disk,
+ their size, and whether they are contiguous on the disk or not.</para>
+ <para><emphasis role="italic"><emphasis role="bold">Example:</emphasis></emphasis></para>
+ <para>Enter on the OSS:</para>
+ <screen># lctl get_param obdfilter.testfs-OST0000.brw_stats
+snapshot_time: 1372775039.769045 (secs.usecs)
+ read | write
+pages per bulk r/w rpcs % cum % | rpcs % cum %
+1: 108 100 100 | 39 0 0
+2: 0 0 100 | 6 0 0
+4: 0 0 100 | 1 0 0
+8: 0 0 100 | 0 0 0
+16: 0 0 100 | 4 0 0
+32: 0 0 100 | 17 0 0
+64: 0 0 100 | 12 0 0
+128: 0 0 100 | 24 0 0
+256: 0 0 100 | 23142 99 100
+
+ read | write
+discontiguous pages rpcs % cum % | rpcs % cum %
+0: 108 100 100 | 23245 100 100
+
+ read | write
+discontiguous blocks rpcs % cum % | rpcs % cum %
+0: 108 100 100 | 23243 99 99
+1: 0 0 100 | 2 0 100
+
+ read | write
+disk fragmented I/Os ios % cum % | ios % cum %
+0: 94 87 87 | 0 0 0
+1: 14 12 100 | 23243 99 99
+2: 0 0 100 | 2 0 100
+
+ read | write
+disk I/Os in flight ios % cum % | ios % cum %
+1: 14 100 100 | 20896 89 89
+2: 0 0 100 | 1071 4 94
+3: 0 0 100 | 573 2 96
+4: 0 0 100 | 300 1 98
+5: 0 0 100 | 166 0 98
+6: 0 0 100 | 108 0 99
+7: 0 0 100 | 81 0 99
+8: 0 0 100 | 47 0 99
+9: 0 0 100 | 5 0 100
+
+ read | write
+I/O time (1/1000s) ios % cum % | ios % cum %
+1: 94 87 87 | 0 0 0
+2: 0 0 87 | 7 0 0
+4: 14 12 100 | 27 0 0
+8: 0 0 100 | 14 0 0
+16: 0 0 100 | 31 0 0
+32: 0 0 100 | 38 0 0
+64: 0 0 100 | 18979 81 82
+128: 0 0 100 | 943 4 86
+256: 0 0 100 | 1233 5 91
+512: 0 0 100 | 1825 7 99
+1K: 0 0 100 | 99 0 99
+2K: 0 0 100 | 0 0 99
+4K: 0 0 100 | 0 0 99
+8K: 0 0 100 | 49 0 100
+
+ read | write
+disk I/O size ios % cum % | ios % cum %
+4K: 14 100 100 | 41 0 0
+8K: 0 0 100 | 6 0 0
+16K: 0 0 100 | 1 0 0
+32K: 0 0 100 | 0 0 0
+64K: 0 0 100 | 4 0 0
+128K: 0 0 100 | 17 0 0
+256K: 0 0 100 | 12 0 0
+512K: 0 0 100 | 24 0 0
+1M: 0 0 100 | 23142 99 100
</screen>
-<note><para>Statistics for all mounted file systems can be discovered by issuing the lctl command: <literal>lctl get_param llite.*.stats</literal></para></note>
+ <para>The tabular data is described in the table below. Each row in the table shows the number
+ of reads and writes occurring for the statistic (<literal>ios</literal>), the relative
+ percentage of total reads or writes (<literal>%</literal>), and the cumulative percentage to
+ that point in the table for the statistic (<literal>cum %</literal>). </para>
<informaltable frame="all">
<tgroup cols="2">
- <colspec colname="c1" colwidth="3*"/>
- <colspec colname="c2" colwidth="7*"/>
+ <colspec colname="c1" colwidth="40*"/>
+ <colspec colname="c2" colwidth="60*"/>
<thead>
<row>
<entry>
<tbody>
<row>
<entry>
- <para> <literal>snapshot_time</literal></para>
- </entry>
- <entry>
- <para>Unix epoch instant the stats file was read.</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal>dirty_page_hits</literal></para>
+ <para>
+ <literal>pages per bulk r/w</literal></para>
</entry>
<entry>
- <para>A count of the number of write operations that have been satisfied by the dirty page cache. See <xref linkend='lustreproc.maxdirtymb'/> for dirty cache behavior in Lustre.</para>
+ <para>Number of pages per RPC request, which should match aggregate client
+ <literal>rpc_stats</literal> (see <xref
+ xmlns:xlink="http://www.w3.org/1999/xlink" linkend="MonitoringClientRCPStream"
+ />).</para>
</entry>
</row>
<row>
<entry>
- <para> <literal>dirty_page_misses</literal></para>
- </entry>
- <entry>
- <para>A count of the number of write operations that were not satisfied by the dirty page cache.</para>
+ <para>
+ <literal>discontiguous pages</literal></para>
</entry>
- </row>
- <row>
<entry>
- <para> <literal>read_bytes</literal></para>
- </entry>
- <entry>
- <para>A count of the number of read operations that have occurred (samples). Three additional parameters are given:</para>
- <variablelist>
- <varlistentry>
- <term>min</term>
- <listitem><para>The minimum number of bytes read in a single request since the counter was reset.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>max</term>
- <listitem><para>The maximum number of bytes read in a single request since the counter was reset.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>sum</term>
- <listitem><para>The accumulated sum of bytes of all read requests since the counter was reset.</para>
- </listitem>
- </varlistentry>
- </variablelist>
+ <para>Number of discontinuities in the logical file offset of each page in a single
+ RPC.</para>
</entry>
</row>
<row>
<entry>
- <para> <literal>write_bytes</literal></para>
- </entry>
- <entry>
- <para>A count of the number of write operations that have occurred (samples). Three additional parameters are given:</para>
- <variablelist>
- <varlistentry>
- <term>min</term>
- <listitem><para>The minimum number of bytes written in a single request since the counter was reset.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>max</term>
- <listitem><para>The maximum number of bytes written in a single request since the counter was reset.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>sum</term>
- <listitem><para>The accumulated sum of bytes of all write requests since the counter was reset.</para>
- </listitem>
- </varlistentry>
- </variablelist>
+ <para>
+ <literal>discontiguous blocks</literal></para>
</entry>
- </row>
- <row>
<entry>
- <para> <literal>brw_read</literal></para>
- </entry>
- <entry>
- <para>A count of the number of pages that have been read.</para> <warning><para><literal>brw_</literal> stats are only tallied when the lloop device driver is present. lloop device is not currently supported.</para></warning><para>Three additional parameters are given:</para>
- <variablelist>
- <varlistentry>
- <term>min</term>
- <listitem><para>The minimum number of bytes read in a single brw read requests since the counter was reset.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>max</term>
- <listitem><para>The maximum number of bytes read in a single brw read requests since the counter was reset.</para>
- </listitem>
- </varlistentry>
- <varlistentry>
- <term>sum</term>
- <listitem><para>The accumulated sum of bytes of all brw read requests since the counter was reset.</para>
- </listitem>
- </varlistentry>
- </variablelist>
+ <para>Number of discontinuities in the physical block allocation in the file system
+ for a single RPC.</para>
</entry>
</row>
<row>
<entry>
- <para> <literal>ioctl</literal></para>
+ <para><literal>disk fragmented I/Os</literal></para>
</entry>
<entry>
- <para>A count of the number of the combined file and directory ioctl operations.</para>
+ <para>Number of I/Os that were not written entirely sequentially.</para>
</entry>
</row>
<row>
<entry>
- <para> <literal>open</literal></para>
+ <para><literal>disk I/Os in flight</literal></para>
</entry>
<entry>
- <para>A count of the number of open operations that have succeeded.</para>
+ <para>Number of disk I/Os currently pending.</para>
</entry>
</row>
<row>
<entry>
- <para> <literal>close</literal></para>
+ <para><literal>I/O time (1/1000s)</literal></para>
</entry>
<entry>
- <para>A count of the number of close operations that have succeeded.</para>
+ <para>Amount of time for each I/O operation to complete.</para>
</entry>
</row>
<row>
<entry>
- <para> <literal>seek</literal></para>
+ <para><literal>disk I/O size</literal></para>
</entry>
<entry>
- <para>A count of the number of times <literal>seek</literal> has been called.</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal>fsync</literal></para>
- </entry>
- <entry>
- <para>A count of the number of times <literal>fsync</literal> has been called.</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal>truncate</literal></para>
- </entry>
- <entry>
- <para>A count of the total number of calls to both locked and lockless truncate.</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal>setxattr</literal></para>
- </entry>
- <entry>
- <para>A count of the number of times <literal>ll_setxattr</literal> has been called.</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal>getxattr</literal></para>
- </entry>
- <entry>
- <para>A count of the number of times <literal>ll_getxattr</literal> has been called.</para>
+ <para>Size of each I/O operation.</para>
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
+ <para><emphasis role="italic"><emphasis role="bold">Analysis:</emphasis></emphasis></para>
+ <para>This data provides an indication of extent size and distribution in the file
+ system.</para>
</section>
- <section remap="h3">
- <title><indexterm><primary>proc</primary><secondary>read/write survey</secondary></indexterm>Client Read-Write Extents Survey</title>
- <para><emphasis role="bold">Client-Based I/O Extent Size Survey</emphasis></para>
- <para>The <literal>rw_extent_stats</literal> histogram in the <literal>llite</literal> directory shows you the statistics for the sizes of the read-write I/O extents. This file does not maintain the per-process statistics.</para>
- <para>Example:</para>
- <screen>client# lctl get_param llite.testfs-*.extents_stats
-snapshot_time: 1213828728.348516 (secs.usecs)
- read | write
-extents calls % cum% | calls % cum%
-
-0K - 4K : 0 0 0 | 2 2 2
-4K - 8K : 0 0 0 | 0 0 2
-8K - 16K : 0 0 0 | 0 0 2
-16K - 32K : 0 0 0 | 20 23 26
-32K - 64K : 0 0 0 | 0 0 26
-64K - 128K : 0 0 0 | 51 60 86
-128K - 256K : 0 0 0 | 0 0 86
-256K - 512K : 0 0 0 | 0 0 86
-512K - 1024K : 0 0 0 | 0 0 86
-1M - 2M : 0 0 0 | 11 13 100</screen>
- <para>The file can be cleared by issuing the following command:</para>
- <screen>client# lctl set_param llite.testfs-*.extents_stats=0</screen>
- <para><emphasis role="bold">Per-Process Client I/O Statistics</emphasis></para>
- <para>The <literal>extents_stats_per_process</literal> file maintains the I/O extent size statistics on a per-process basis. So you can track the per-process statistics for the last <literal>MAX_PER_PROCESS_HIST</literal> processes.</para>
- <para>Example:</para>
- <screen>lctl get_param llite.testfs-*.extents_stats_per_process
-snapshot_time: 1213828762.204440 (secs.usecs)
- read | write
-extents calls % cum% | calls % cum%
-
-PID: 11488
- 0K - 4K : 0 0 0 | 0 0 0
- 4K - 8K : 0 0 0 | 0 0 0
- 8K - 16K : 0 0 0 | 0 0 0
- 16K - 32K : 0 0 0 | 0 0 0
- 32K - 64K : 0 0 0 | 0 0 0
- 64K - 128K : 0 0 0 | 0 0 0
- 128K - 256K : 0 0 0 | 0 0 0
- 256K - 512K : 0 0 0 | 0 0 0
- 512K - 1024K : 0 0 0 | 0 0 0
- 1M - 2M : 0 0 0 | 10 100 100
-
-PID: 11491
- 0K - 4K : 0 0 0 | 0 0 0
- 4K - 8K : 0 0 0 | 0 0 0
- 8K - 16K : 0 0 0 | 0 0 0
- 16K - 32K : 0 0 0 | 20 100 100
-
-PID: 11424
- 0K - 4K : 0 0 0 | 0 0 0
- 4K - 8K : 0 0 0 | 0 0 0
- 8K - 16K : 0 0 0 | 0 0 0
- 16K - 32K : 0 0 0 | 0 0 0
- 32K - 64K : 0 0 0 | 0 0 0
- 64K - 128K : 0 0 0 | 16 100 100
-
-PID: 11426
- 0K - 4K : 0 0 0 | 1 100 100
-
-PID: 11429
- 0K - 4K : 0 0 0 | 1 100 100
-
-</screen>
- </section>
- <section xml:id="dbdoclet.50438271_55057">
- <title><indexterm><primary>proc</primary><secondary>block I/O</secondary></indexterm>Watching the OST Block I/O Stream</title>
- <para>Similarly, there is a <literal>brw_stats</literal> histogram in the obdfilter directory which shows you the statistics for number of I/O requests sent to the disk, their size and whether they are contiguous on the disk or not.</para>
- <screen>oss# lctl get_param obdfilter.testfs-OST0000.brw_stats
-snapshot_time: 1174875636.764630 (secs:usecs)
- read write
-pages per brw brws % cum % | rpcs % cum %
-1: 0 0 0 | 0 0 0
- read write
-discont pages rpcs % cum % | rpcs % cum %
-1: 0 0 0 | 0 0 0
- read write
-discont blocks rpcs % cum % | rpcs % cum %
-1: 0 0 0 | 0 0 0
- read write
-dio frags rpcs % cum % | rpcs % cum %
-1: 0 0 0 | 0 0 0
- read write
-disk ios in flight rpcs % cum % | rpcs % cum %
-1: 0 0 0 | 0 0 0
- read write
-io time (1/1000s) rpcs % cum % | rpcs % cum %
-1: 0 0 0 | 0 0 0
- read write
-disk io size rpcs % cum % | rpcs % cum %
-1: 0 0 0 | 0 0 0
- read write
-</screen>
- <para>The fields are explained below:</para>
- <informaltable frame="all">
- <tgroup cols="2">
- <colspec colname="c1" colwidth="50*"/>
- <colspec colname="c2" colwidth="50*"/>
- <thead>
- <row>
- <entry>
- <para><emphasis role="bold">Field</emphasis></para>
- </entry>
- <entry>
- <para><emphasis role="bold">Description</emphasis></para>
- </entry>
- </row>
- </thead>
- <tbody>
- <row>
- <entry>
- <para> <literal> pages per brw </literal></para>
- </entry>
- <entry>
- <para>Number of pages per RPC request, which should match aggregate client <literal>rpc_stats</literal>.</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> discont pages </literal></para>
- </entry>
- <entry>
- <para>Number of discontinuities in the logical file offset of each page in a single RPC.</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> discont blocks </literal></para>
- </entry>
- <entry>
- <para>Number of discontinuities in the physical block allocation in the file system for a single RPC.</para>
- </entry>
- </row>
- </tbody>
- </tgroup>
- </informaltable>
- <para>For each Lustre service, the following information is provided:</para>
- <itemizedlist>
- <listitem>
- <para>Number of requests</para>
- </listitem>
- <listitem>
- <para>Request wait time (avg, min, max and std dev)</para>
- </listitem>
- <listitem>
- <para>Service idle time (% of elapsed time)</para>
- </listitem>
- </itemizedlist>
- <para>Additionally, data on each Lustre service is provided by service type:</para>
- <itemizedlist>
- <listitem>
- <para>Number of requests of this type</para>
- </listitem>
- <listitem>
- <para>Request service time (avg, min, max and std dev)</para>
- </listitem>
- </itemizedlist>
+ </section>
+ <section>
+ <title>Tuning Lustre File System I/O</title>
+ <para>Each OSC has its own tree of tunables. For example:</para>
+ <screen>$ ls -d /proc/fs/testfs/osc/OSC_client_ost1_MNT_client_2 /localhost
+/proc/fs/testfs/osc/OSC_uml0_ost1_MNT_localhost
+/proc/fs/testfs/osc/OSC_uml0_ost2_MNT_localhost
+/proc/fs/testfs/osc/OSC_uml0_ost3_MNT_localhost
+
+$ ls /proc/fs/testfs/osc/OSC_uml0_ost1_MNT_localhost
+blocksizefilesfree max_dirty_mb ost_server_uuid stats
+
+...</screen>
+ <para>The following sections describe some of the parameters that can be tuned in a Lustre file
+ system.</para>
+ <section remap="h3" xml:id="TuningClientIORPCStream">
+ <title><indexterm>
+ <primary>proc</primary>
+ <secondary>RPC tunables</secondary>
+ </indexterm>Tuning the Client I/O RPC Stream</title>
+ <para>Ideally, an optimal amount of data is packed into each I/O RPC and a consistent number
+ of issued RPCs are in progress at any time. To help optimize the client I/O RPC stream,
+ several tuning variables are provided to adjust behavior according to network conditions and
+ cluster size. For information about monitoring the client I/O RPC stream, see <xref
+ xmlns:xlink="http://www.w3.org/1999/xlink" linkend="MonitoringClientRCPStream"/>.</para>
+ <para>RPC stream tunables include:</para>
+ <para>
+ <itemizedlist>
+ <listitem>
+ <para><literal>osc.<replaceable>osc_instance</replaceable>.max_dirty_mb</literal> -
+ Controls how many MBs of dirty data can be written and queued up in the OSC. POSIX
+ file writes that are cached contribute to this count. When the limit is reached,
+ additional writes stall until previously-cached writes are written to the server. This
+ may be changed by writing a single ASCII integer to the file. Only values between 0
+ and 2048 or 1/4 of RAM are allowable. If 0 is specified, no writes are cached.
+ Performance suffers noticeably unless you use large writes (1 MB or more).</para>
+ <para>To maximize performance, the value for <literal>max_dirty_mb</literal> is
+ recommended to be 4 * <literal>max_pages_per_rpc </literal>*
+ <literal>max_rpcs_in_flight</literal>.</para>
+ </listitem>
+ <listitem>
+ <para><literal>osc.<replaceable>osc_instance</replaceable>.cur_dirty_bytes</literal> - A
+ read-only value that returns the current number of bytes written and cached on this
+ OSC.</para>
+ </listitem>
+ <listitem>
+ <para><literal>osc.<replaceable>osc_instance</replaceable>.max_pages_per_rpc</literal> -
+ The maximum number of pages that will undergo I/O in a single RPC to the OST. The
+ minimum setting is a single page and the maximum setting is 1024 (for systems with a
+ <literal>PAGE_SIZE</literal> of 4 KB), with the default maximum of 1 MB in the RPC.
+ It is also possible to specify a units suffix (e.g. <literal>4M</literal>), so that
+ the RPC size can be specified independently of the client
+ <literal>PAGE_SIZE</literal>.</para>
+ </listitem>
+ <listitem>
+ <para><literal>osc.<replaceable>osc_instance</replaceable>.max_rpcs_in_flight</literal>
+ - The maximum number of concurrent RPCs in flight from an OSC to its OST. If the OSC
+ tries to initiate an RPC but finds that it already has the same number of RPCs
+ outstanding, it will wait to issue further RPCs until some complete. The minimum
+ setting is 1 and maximum setting is 256. </para>
+ <para>To improve small file I/O performance, increase the
+ <literal>max_rpcs_in_flight</literal> value.</para>
+ </listitem>
+ <listitem>
+ <para><literal>llite.<replaceable>fsname-instance</replaceable>/max_cache_mb</literal> -
+ Maximum amount of inactive data cached by the client (default is 3/4 of RAM). For
+ example:</para>
+ <screen># lctl get_param llite.testfs-ce63ca00.max_cached_mb
+128</screen>
+ </listitem>
+ </itemizedlist>
+ </para>
+ <note>
+ <para>The value for <literal><replaceable>osc_instance</replaceable></literal> is typically
+ <literal><replaceable>fsname</replaceable>-OST<replaceable>ost_index</replaceable>-osc-<replaceable>mountpoint_instance</replaceable></literal>,
+ where the value for <literal><replaceable>mountpoint_instance</replaceable></literal> is
+ unique to each mount point to allow associating osc, mdc, lov, lmv, and llite parameters
+ with the same mount point. For
+ example:<screen>lctl get_param osc.testfs-OST0000-osc-ffff88107412f400.rpc_stats
+osc.testfs-OST0000-osc-ffff88107412f400.rpc_stats=
+snapshot_time: 1375743284.337839 (secs.usecs)
+read RPCs in flight: 0
+write RPCs in flight: 0
+</screen></para>
+ </note>
</section>
<section remap="h3">
- <title><indexterm><primary>proc</primary><secondary>readahead</secondary></indexterm>Using File Readahead and Directory Statahead</title>
- <para>Lustre 1.6.5.1 introduced file readahead and directory statahead functionality that read data into memory in anticipation of a process actually requesting the data. File readahead functionality reads file content data into memory. Directory statahead functionality reads metadata into memory. When readahead and/or statahead work well, a data-consuming process finds that the information it needs is available when requested, and it is unnecessary to wait for network I/O.</para>
- <para>Since Lustre 2.2.0, the directory statahead feature has been improved to enhance directory traversal performance. The improvements have concentrated on two main issues:</para>
- <orderedlist>
+ <title><indexterm>
+ <primary>proc</primary>
+ <secondary>readahead</secondary>
+ </indexterm>Tuning File Readahead and Directory Statahead</title>
+ <para>File readahead and directory statahead enable reading of data into memory before a
+ process requests the data. File readahead reads file content data into memory and directory
+ statahead reads metadata into memory. When readahead and statahead work well, a process that
+ accesses data finds that the information it needs is available immediately when requested in
+ memory without the delay of network I/O.</para>
+ <para condition="l22">In Lustre release 2.2.0, the directory statahead feature was improved to
+ enhance directory traversal performance. The improvements primarily addressed two
+ issues:</para>
+ <orderedlist condition="l22">
<listitem>
- <para>A race condition between statahead thread and other VFS operations while processing asynchronous getattr RPC replies.</para>
+ <para>A race condition existed between the statahead thread and other VFS operations while
+ processing asynchronous <literal>getattr</literal> RPC replies, causing duplicate
+ entries in dcache. This issue was resolved by using statahead local dcache. </para>
</listitem>
<listitem>
- <para>There is no file size/block attributes pre-fetching and the traversing thread has to send synchronous glimpse size RPCs to OST(s).</para>
+ <para>File size/block attributes pre-fetching was not supported, so the traversing thread
+ had to send synchronous glimpse size RPCs to OST(s). This issue was resolved by using
+ asynchronous glimpse lock (AGL) RPCs to pre-fetch file size/block attributes from
+ OST(s).</para>
</listitem>
</orderedlist>
- <para>The first issue is resolved by using statahead local dcache, and the second one is resolved by using asynchronous glimpse lock (AGL) RPCs for pre-fetching file size/block attributes from OST(s).</para>
<section remap="h4">
<title>Tuning File Readahead</title>
- <para>File readahead is triggered when two or more sequential reads by an application fail to be satisfied by the Linux buffer cache. The size of the initial readahead is 1 MB. Additional readaheads grow linearly, and increment until the readahead cache on the client is full at 40 MB.</para>
- <para><literal> llite.<replaceable>fsname-instance</replaceable>.max_read_ahead_mb </literal></para>
- <para>This tunable controls the maximum amount of data readahead on a file. Files are read ahead in RPC-sized chunks (1 MB or the size of read() call, if larger) after the second sequential read on a file descriptor. Random reads are done at the size of the read() call only (no readahead). Reads to non-contiguous regions of the file reset the readahead algorithm, and readahead is not triggered again until there are sequential reads again. To disable readahead, set this tunable to 0. The default value is 40 MB.</para>
- <para><literal> llite.<replaceable>fsname-instance</replaceable>.max_read_ahead_whole_mb </literal></para>
- <para>This tunable controls the maximum size of a file that is read in its entirety, regardless of the size of the <literal>read()</literal>.</para>
+ <para>File readahead is triggered when two or more sequential reads by an application fail
+ to be satisfied by data in the Linux buffer cache. The size of the initial readahead is 1
+ MB. Additional readaheads grow linearly and increment until the readahead cache on the
+ client is full at 40 MB.</para>
+ <para>Readahead tunables include:</para>
+ <itemizedlist>
+ <listitem>
+ <para><literal>llite.<replaceable>fsname-instance</replaceable>.max_read_ahead_mb</literal>
+ - Controls the maximum amount of data readahead on a file. Files are read ahead in
+ RPC-sized chunks (1 MB or the size of the <literal>read()</literal> call, if larger)
+ after the second sequential read on a file descriptor. Random reads are done at the
+ size of the <literal>read()</literal> call only (no readahead). Reads to
+ non-contiguous regions of the file reset the readahead algorithm, and readahead is not
+ triggered again until sequential reads take place again. </para>
+ <para>To disable readahead, set this tunable to 0. The default value is 40 MB.</para>
+ </listitem>
+ <listitem>
+ <para><literal>llite.<replaceable>fsname-instance</replaceable>.max_read_ahead_whole_mb</literal>
+ - Controls the maximum size of a file that is read in its entirety, regardless of the
+ size of the <literal>read()</literal>.</para>
+ </listitem>
+ </itemizedlist>
</section>
- <section remap="h4">
+ <section>
<title>Tuning Directory Statahead and AGL</title>
- <para>Many system commands, like <literal>ls –l</literal>, <literal>du</literal>, <literal>find</literal>, etc., will traverse directory sequentially. To make these commands run efficiently, the directory statahead and AGL (asynchronous glimpse lock) can be enabled to improve the performance of traversing.</para>
- <para><literal> /proc/fs/lustre/llite/*/statahead_max </literal></para>
- <para>This proc interface controls whether directory statahead is enabled and the maximum statahead windows size (which means how many files can be pre-fetched by the statahead thread). By default, statahead is enabled and the value of <literal>statahead_max</literal> is 32.</para>
- <para>To disable statahead, run:</para>
- <screen>lctl set_param llite.*.statahead_max=0</screen>
- <para>To set the maximum statahead windows size (n), run:</para>
- <screen>lctl set_param llite.*.statahead_max=n</screen>
- <para>The maximum value of n is 8192.</para>
- <para>The AGL can be controlled as follows:</para>
- <screen>lctl set_param llite.*.statahead_agl=n</screen>
- <para>If "n" is 0, then the AGL is disabled, else the AGL is enabled.</para>
- <para><literal> /proc/fs/lustre/llite/*/statahead_stats </literal></para>
- <para>This is a read-only interface that indicates the current statahead and AGL status.</para>
- <note>
- <para>The AGL is affected by statahead because the inodes processed by AGL are built by the statahead thread, which means the statahead thread is the input of AGL pipeline. So if statahead is disabled, then the AGL is disabled by force.</para>
- </note>
+ <para>Many system commands, such as <literal>ls –l</literal>, <literal>du</literal>, and
+ <literal>find</literal>, traverse a directory sequentially. To make these commands run
+ efficiently, the directory statahead and asynchronous glimpse lock (AGL) can be enabled to
+ improve the performance of traversing.</para>
+ <para>The statahead tunables are:</para>
+ <itemizedlist>
+ <listitem>
+ <para><literal>statahead_max</literal> - Controls whether directory statahead is enabled
+ and the maximum statahead window size (i.e., how many files can be pre-fetched by the
+ statahead thread). By default, statahead is enabled and the value of
+ <literal>statahead_max</literal> is 32.</para>
+ <para>To disable statahead, run:</para>
+ <screen>lctl set_param llite.*.statahead_max=0</screen>
+ <para>To set the maximum statahead window size (<replaceable>n</replaceable>),
+ run:</para>
+ <screen>lctl set_param llite.*.statahead_max=<replaceable>n</replaceable></screen>
+ <para>The maximum value of <replaceable>n</replaceable> is 8192.</para>
+ <para>The AGL can be controlled by entering:</para>
+ <screen>lctl set_param llite.*.statahead_agl=<replaceable>n</replaceable></screen>
+ <para>The default value for <replaceable>n</replaceable> is 1, which enables the AGL. If
+ <replaceable>n</replaceable> is 0, the AGL is disabled.</para>
+ </listitem>
+ <listitem>
+ <para><literal>statahead_stats</literal> - A read-only interface that indicates the
+ current statahead and AGL statistics, such as how many times statahead/AGL has been
+ triggered since the last mount, how many statahead/AGL failures have occurred due to
+ an incorrect prediction or other causes.</para>
+ <note>
+ <para>The AGL is affected by statahead because the inodes processed by AGL are built
+ by the statahead thread, which means the statahead thread is the input of the AGL
+ pipeline. So if statahead is disabled, then the AGL is disabled by force.</para>
+ </note>
+ </listitem>
+ </itemizedlist>
</section>
</section>
<section remap="h3">
- <title><indexterm><primary>proc</primary><secondary>read cache</secondary></indexterm>OSS Read Cache</title>
- <para>The OSS read cache feature provides read-only caching of data on an OSS. This functionality uses the regular Linux page cache to store the data. Just like caching from a regular filesystem in Linux, OSS read cache uses as much physical memory as is allocated.</para>
- <para>OSS read cache improves Lustre performance in these situations:</para>
+ <title><indexterm>
+ <primary>proc</primary>
+ <secondary>read cache</secondary>
+ </indexterm>Tuning OSS Read Cache</title>
+ <para>The OSS read cache feature provides read-only caching of data on an OSS. This
+ functionality uses the Linux page cache to store the data and uses as much physical memory
+ as is allocated.</para>
+ <para>OSS read cache improves Lustre file system performance in these situations:</para>
<itemizedlist>
<listitem>
- <para>Many clients are accessing the same data set (as in HPC applications and when diskless clients boot from Lustre)</para>
+ <para>Many clients are accessing the same data set (as in HPC applications or when
+ diskless clients boot from the Lustre file system).</para>
</listitem>
<listitem>
- <para>One client is storing data while another client is reading it (essentially exchanging data via the OST)</para>
+ <para>One client is storing data while another client is reading it (i.e., clients are
+ exchanging data via the OST).</para>
</listitem>
<listitem>
- <para>A client has very limited caching of its own</para>
+ <para>A client has very limited caching of its own.</para>
</listitem>
</itemizedlist>
<para>OSS read cache offers these benefits:</para>
<itemizedlist>
<listitem>
- <para>Allows OSTs to cache read data more frequently</para>
+ <para>Allows OSTs to cache read data more frequently.</para>
</listitem>
<listitem>
- <para>Improves repeated reads to match network speeds instead of disk speeds</para>
+ <para>Improves repeated reads to match network speeds instead of disk speeds.</para>
</listitem>
<listitem>
- <para>Provides the building blocks for OST write cache (small-write aggregation)</para>
+ <para>Provides the building blocks for OST write cache (small-write aggregation).</para>
</listitem>
</itemizedlist>
<section remap="h4">
<title>Using OSS Read Cache</title>
- <para>OSS read cache is implemented on the OSS, and does not require any special support on the client side. Since OSS read cache uses the memory available in the Linux page cache, you should use I/O patterns to determine the appropriate amount of memory for the cache; if the data is mostly reads, then more cache is required than for writes.</para>
- <para>OSS read cache is enabled, by default, and managed by the following tunables:</para>
+ <para>OSS read cache is implemented on the OSS, and does not require any special support on
+ the client side. Since OSS read cache uses the memory available in the Linux page cache,
+ the appropriate amount of memory for the cache should be determined based on I/O patterns;
+ if the data is mostly reads, then more cache is required than would be needed for mostly
+ writes.</para>
+ <para>OSS read cache is managed using the following tunables:</para>
<itemizedlist>
<listitem>
- <para><literal>read_cache_enable</literal> controls whether data read from disk during a read request is kept in memory and available for later read requests for the same data, without having to re-read it from disk. By default, read cache is enabled (<literal>read_cache_enable = 1</literal>).</para>
+ <para><literal>read_cache_enable</literal> - Controls whether data read from disk during
+ a read request is kept in memory and available for later read requests for the same
+ data, without having to re-read it from disk. By default, read cache is enabled
+ (<literal>read_cache_enable=1</literal>).</para>
+ <para>When the OSS receives a read request from a client, it reads data from disk into
+ its memory and sends the data as a reply to the request. If read cache is enabled,
+ this data stays in memory after the request from the client has been fulfilled. When
+ subsequent read requests for the same data are received, the OSS skips reading data
+ from disk and the request is fulfilled from the cached data. The read cache is managed
+ by the Linux kernel globally across all OSTs on that OSS so that the least recently
+ used cache pages are dropped from memory when the amount of free memory is running
+ low.</para>
+ <para>If read cache is disabled (<literal>read_cache_enable=0</literal>), the OSS
+ discards the data after a read request from the client is serviced and, for subsequent
+ read requests, the OSS again reads the data from disk.</para>
+ <para>To disable read cache on all the OSTs of an OSS, run:</para>
+ <screen>root@oss1# lctl set_param obdfilter.*.read_cache_enable=0</screen>
+ <para>To re-enable read cache on one OST, run:</para>
+ <screen>root@oss1# lctl set_param obdfilter.{OST_name}.read_cache_enable=1</screen>
+ <para>To check if read cache is enabled on all OSTs on an OSS, run:</para>
+ <screen>root@oss1# lctl get_param obdfilter.*.read_cache_enable</screen>
</listitem>
- </itemizedlist>
- <para>When the OSS receives a read request from a client, it reads data from disk into its memory and sends the data as a reply to the requests. If read cache is enabled, this data stays in memory after the client's request is finished, and the OSS skips reading data from disk when subsequent read requests for the same are received. The read cache is managed by the Linux kernel globally across all OSTs on that OSS, and the least recently used cache pages will be dropped from memory when the amount of free memory is running low.</para>
- <para>If read cache is disabled (<literal>read_cache_enable = 0</literal>), then the OSS will discard the data after the client's read requests are serviced and, for subsequent read requests, the OSS must read the data from disk.</para>
- <para>To disable read cache on all OSTs of an OSS, run:</para>
- <screen>root@oss1# lctl set_param obdfilter.*.read_cache_enable=0</screen>
- <para>To re-enable read cache on one OST, run:</para>
- <screen>root@oss1# lctl set_param obdfilter.{OST_name}.read_cache_enable=1</screen>
- <para>To check if read cache is enabled on all OSTs on an OSS, run:</para>
- <screen>root@oss1# lctl get_param obdfilter.*.read_cache_enable</screen>
- <itemizedlist>
<listitem>
- <para><literal>writethrough_cache_enable</literal> controls whether data sent to the OSS as a write request is kept in the read cache and available for later reads, or if it is discarded from cache when the write is completed. By default, writethrough cache is enabled (<literal>writethrough_cache_enable = 1</literal>).</para>
+ <para><literal>writethrough_cache_enable</literal> - Controls whether data sent to the
+ OSS as a write request is kept in the read cache and available for later reads, or if
+ it is discarded from cache when the write is completed. By default, the writethrough
+ cache is enabled (<literal>writethrough_cache_enable=1</literal>).</para>
+ <para>When the OSS receives write requests from a client, it receives data from the
+ client into its memory and writes the data to disk. If the writethrough cache is
+ enabled, this data stays in memory after the write request is completed, allowing the
+ OSS to skip reading this data from disk if a later read request, or partial-page write
+ request, for the same data is received.</para>
+ <para>If the writethrough cache is disabled
+ (<literal>writethrough_cache_enabled=0</literal>), the OSS discards the data after
+ the write request from the client is completed. For subsequent read requests, or
+ partial-page write requests, the OSS must re-read the data from disk.</para>
+ <para>Enabling writethrough cache is advisable if clients are doing small or unaligned
+ writes that would cause partial-page updates, or if the files written by one node are
+ immediately being accessed by other nodes. Some examples where enabling writethrough
+ cache might be useful include producer-consumer I/O models or shared-file writes with
+ a different node doing I/O not aligned on 4096-byte boundaries. </para>
+ <para>Disabling the writethrough cache is advisable when files are mostly written to the
+ file system but are not re-read within a short time period, or files are only written
+ and re-read by the same node, regardless of whether the I/O is aligned or not.</para>
+ <para>To disable the writethrough cache on all OSTs of an OSS, run:</para>
+ <screen>root@oss1# lctl set_param obdfilter.*.writethrough_cache_enable=0</screen>
+ <para>To re-enable the writethrough cache on one OST, run:</para>
+ <screen>root@oss1# lctl set_param obdfilter.{OST_name}.writethrough_cache_enable=1</screen>
+ <para>To check if the writethrough cache is enabled, run:</para>
+ <screen>root@oss1# lctl set_param obdfilter.*.writethrough_cache_enable=1</screen>
</listitem>
- </itemizedlist>
- <para>When the OSS receives write requests from a client, it receives data from the client into its memory and writes the data to disk. If writethrough cache is enabled, this data stays in memory after the write request is completed, allowing the OSS to skip reading this data from disk if a later read request, or partial-page write request, for the same data is received.</para>
- <para>If writethrough cache is disabled (<literal>writethrough_cache_enabled = 0</literal>), then the OSS discards the data after the client's write request is completed, and for subsequent read request, or partial-page write request, the OSS must re-read the data from disk.</para>
- <para>Enabling writethrough cache is advisable if clients are doing small or unaligned writes that would cause partial-page updates, or if the files written by one node are immediately being accessed by other nodes. Some examples where this might be useful include producer-consumer I/O models or shared-file writes with a different node doing I/O not aligned on 4096-byte boundaries. Disabling writethrough cache is advisable in the case where files are mostly written to the file system but are not re-read within a short time period, or files are only written and re-read by the same node, regardless of whether the I/O is aligned or not.</para>
- <para>To disable writethrough cache on all OSTs of an OSS, run:</para>
- <screen>root@oss1# lctl set_param obdfilter.*.writethrough_cache_enable=0</screen>
- <para>To re-enable writethrough cache on one OST, run:</para>
- <screen>root@oss1# lctl set_param \
-obdfilter.{OST_name}.writethrough_cache_enable=1</screen>
- <para>To check if writethrough cache is</para>
- <screen>root@oss1# lctl set_param obdfilter.*.writethrough_cache_enable=1</screen>
- <itemizedlist>
<listitem>
- <para><literal>readcache_max_filesize</literal> controls the maximum size of a file that both the read cache and writethrough cache will try to keep in memory. Files larger than <literal>readcache_max_filesize</literal> will not be kept in cache for either reads or writes.</para>
+ <para><literal>readcache_max_filesize</literal> - Controls the maximum size of a file
+ that both the read cache and writethrough cache will try to keep in memory. Files
+ larger than <literal>readcache_max_filesize</literal> will not be kept in cache for
+ either reads or writes.</para>
+ <para>Setting this tunable can be useful for workloads where relatively small files are
+ repeatedly accessed by many clients, such as job startup files, executables, log
+ files, etc., but large files are read or written only once. By not putting the larger
+ files into the cache, it is much more likely that more of the smaller files will
+ remain in cache for a longer time.</para>
+ <para>When setting <literal>readcache_max_filesize</literal>, the input value can be
+ specified in bytes, or can have a suffix to indicate other binary units such as
+ <literal>K</literal> (kilobytes), <literal>M</literal> (megabytes),
+ <literal>G</literal> (gigabytes), <literal>T</literal> (terabytes), or
+ <literal>P</literal> (petabytes).</para>
+ <para>To limit the maximum cached file size to 32 MB on all OSTs of an OSS, run:</para>
+ <screen>root@oss1# lctl set_param obdfilter.*.readcache_max_filesize=32M</screen>
+ <para>To disable the maximum cached file size on an OST, run:</para>
+ <screen>root@oss1# lctl set_param obdfilter.{OST_name}.readcache_max_filesize=-1</screen>
+ <para>To check the current maximum cached file size on all OSTs of an OSS, run:</para>
+ <screen>root@oss1# lctl get_param obdfilter.*.readcache_max_filesize</screen>
</listitem>
</itemizedlist>
- <para>This can be very useful for workloads where relatively small files are repeatedly accessed by many clients, such as job startup files, executables, log files, etc., but large files are read or written only once. By not putting the larger files into the cache, it is much more likely that more of the smaller files will remain in cache for a longer time.</para>
- <para>When setting <literal>readcache_max_filesize</literal>, the input value can be specified in bytes, or can have a suffix to indicate other binary units such as <emphasis role="bold">K</emphasis>ilobytes, <emphasis role="bold">M</emphasis>egabytes, <emphasis role="bold">G</emphasis>igabytes, <emphasis role="bold">T</emphasis>erabytes, or <emphasis role="bold">P</emphasis>etabytes.</para>
- <para>To limit the maximum cached file size to 32MB on all OSTs of an OSS, run:</para>
- <screen>root@oss1# lctl set_param obdfilter.*.readcache_max_filesize=32M</screen>
- <para>To disable the maximum cached file size on an OST, run:</para>
- <screen>root@oss1# lctl set_param \
-obdfilter.{OST_name}.readcache_max_filesize=-1</screen>
- <para>To check the current maximum cached file size on all OSTs of an OSS, run:</para>
- <screen>root@oss1# lctl get_param obdfilter.*.readcache_max_filesize</screen>
</section>
</section>
- <section remap="h3">
- <title><indexterm><primary>proc</primary><secondary>OSS journal</secondary></indexterm>OSS Asynchronous Journal Commit</title>
- <para>The OSS asynchronous journal commit feature synchronously writes data to disk without forcing a journal flush. This reduces the number of seeks and significantly improves performance on some hardware.</para>
+ <section>
+ <title><indexterm>
+ <primary>proc</primary>
+ <secondary>OSS journal</secondary>
+ </indexterm>Enabling OSS Asynchronous Journal Commit</title>
+ <para>The OSS asynchronous journal commit feature asynchronously writes data to disk without
+ forcing a journal flush. This reduces the number of seeks and significantly improves
+ performance on some hardware.</para>
<note>
- <para>Asynchronous journal commit cannot work with O_DIRECT writes, a journal flush is still forced.</para>
+ <para>Asynchronous journal commit cannot work with direct I/O-originated writes
+ (<literal>O_DIRECT</literal> flag set). In this case, a journal flush is forced. </para>
</note>
- <para>When asynchronous journal commit is enabled, client nodes keep data in the page cache (a page reference). Lustre clients monitor the last committed transaction number (transno) in messages sent from the OSS to the clients. When a client sees that the last committed transno reported by the OSS is at least the bulk write transno, it releases the reference on the corresponding pages. To avoid page references being held for too long on clients after a bulk write, a 7 second ping request is scheduled (jbd commit time is 5 seconds) after the bulk write reply is received, so the OSS has an opportunity to report the last committed transno.</para>
- <para>If the OSS crashes before the journal commit occurs, then the intermediate data is lost. However, new OSS recovery functionality (introduced in the asynchronous journal commit feature), causes clients to replay their write requests and compensate for the missing disk updates by restoring the state of the file system.</para>
- <para>To enable asynchronous journal commit, set the <literal>sync_journal parameter</literal> to zero (<literal>sync_journal=0</literal>):</para>
+ <para>When the asynchronous journal commit feature is enabled, client nodes keep data in the
+ page cache (a page reference). Lustre clients monitor the last committed transaction number
+ (<literal>transno</literal>) in messages sent from the OSS to the clients. When a client
+ sees that the last committed <literal>transno</literal> reported by the OSS is at least
+ equal to the bulk write <literal>transno</literal>, it releases the reference on the
+ corresponding pages. To avoid page references being held for too long on clients after a
+ bulk write, a 7 second ping request is scheduled (the default OSS file system commit time
+ interval is 5 seconds) after the bulk write reply is received, so the OSS has an opportunity
+ to report the last committed <literal>transno</literal>.</para>
+ <para>If the OSS crashes before the journal commit occurs, then intermediate data is lost.
+ However, OSS recovery functionality incorporated into the asynchronous journal commit
+ feature causes clients to replay their write requests and compensate for the missing disk
+ updates by restoring the state of the file system.</para>
+ <para>By default, <literal>sync_journal</literal> is enabled
+ (<literal>sync_journal=1</literal>), so that journal entries are committed synchronously.
+ To enable asynchronous journal commit, set the <literal>sync_journal</literal> parameter to
+ <literal>0</literal> by entering: </para>
<screen>$ lctl set_param obdfilter.*.sync_journal=0
obdfilter.lol-OST0001.sync_journal=0</screen>
- <para>By default, <literal>sync_journal</literal> is disabled (<literal>sync_journal=1</literal>), which forces a journal flush after every bulk write.</para>
- <para>When asynchronous journal commit is used, clients keep a page reference until the journal transaction commits. This can cause problems when a client receives a blocking callback, because pages need to be removed from the page cache, but they cannot be removed because of the extra page reference.</para>
- <para>This problem is solved by forcing a journal flush on lock cancellation. When this happens, the client is granted the metadata blocks that have hit the disk, and it can safely release the page reference before processing the blocking callback. The parameter which controls this action is <literal>sync_on_lock_cancel</literal>, which can be set to the following values:</para>
+ <para>An associated <literal>sync-on-lock-cancel</literal> feature (enabled by default)
+ addresses a data consistency issue that can result if an OSS crashes after multiple clients
+ have written data into intersecting regions of an object, and then one of the clients also
+ crashes. A condition is created in which the POSIX requirement for continuous writes is
+ violated along with a potential for corrupted data. With
+ <literal>sync-on-lock-cancel</literal> enabled, if a cancelled lock has any volatile
+ writes attached to it, the OSS synchronously writes the journal to disk on lock
+ cancellation. Disabling the <literal>sync-on-lock-cancel</literal> feature may enhance
+ performance for concurrent write workloads, but it is recommended that you not disable this
+ feature.</para>
+ <para> The <literal>sync_on_lock_cancel</literal> parameter can be set to the following
+ values:</para>
<itemizedlist>
<listitem>
- <para><literal>always</literal>: Always force a journal flush on lock cancellation</para>
+ <para><literal>always</literal> - Always force a journal flush on lock cancellation
+ (default when <literal>async_journal</literal> is enabled).</para>
</listitem>
<listitem>
- <para><literal>blocking</literal>: Force a journal flush only when the local cancellation is due to a blocking callback</para>
+ <para><literal>blocking</literal> - Force a journal flush only when the local cancellation
+ is due to a blocking callback.</para>
</listitem>
<listitem>
- <para><literal>never</literal>: Do not force any journal flush</para>
+ <para><literal>never</literal> - Do not force any journal flush (default when
+ <literal>async_journal</literal> is disabled).</para>
</listitem>
</itemizedlist>
- <para>Here is an example of <literal>sync_on_lock_cancel</literal> being set not to force a journal flush:</para>
+ <para>For example, to set <literal>sync_on_lock_cancel</literal> to not to force a journal
+ flush, use a command similar to:</para>
<screen>$ lctl get_param obdfilter.*.sync_on_lock_cancel
obdfilter.lol-OST0001.sync_on_lock_cancel=never</screen>
- <para>By default, <literal>sync_on_lock_cancel</literal> is set to never, because asynchronous journal commit is disabled by default.</para>
- <para>When asynchronous journal commit is enabled (<literal>sync_journal=0</literal>), <literal>sync_on_lock_cancel</literal> is automatically set to always, if it was previously set to never.</para>
- <para>Similarly, when asynchronous journal commit is disabled, (<literal>sync_journal=1</literal>), <literal>sync_on_lock_cancel</literal> is enforced to never.</para>
</section>
- <section remap="h3">
- <title><indexterm><primary>proc</primary><secondary>mballoc history</secondary></indexterm><literal>mballoc</literal> History</title>
- <para><literal> /proc/fs/ldiskfs/sda/mb_history </literal></para>
- <para>Multi-Block-Allocate (<literal>mballoc</literal>), enables Lustre to ask <literal>ldiskfs</literal> to allocate multiple blocks with a single request to the block allocator. Typically, an <literal>ldiskfs</literal> file system allocates only one block per time. Each <literal>mballoc</literal>-enabled partition has this file. This is sample output:</para>
- <screen>pid inode goal result found grps cr \ merge tail broken
-2838 139267 17/12288/1 17/12288/1 1 0 0 \ M 1 8192
-2838 139267 17/12289/1 17/12289/1 1 0 0 \ M 0 0
-2838 139267 17/12290/1 17/12290/1 1 0 0 \ M 1 2
-2838 24577 3/12288/1 3/12288/1 1 0 0 \ M 1 8192
-2838 24578 3/12288/1 3/771/1 1 1 1 \ 0 0
-2838 32769 4/12288/1 4/12288/1 1 0 0 \ M 1 8192
-2838 32770 4/12288/1 4/12289/1 13 1 1 \ 0 0
-2838 32771 4/12288/1 5/771/1 26 2 1 \ 0 0
-2838 32772 4/12288/1 5/896/1 31 2 1 \ 1 128
-2838 32773 4/12288/1 5/897/1 31 2 1 \ 0 0
-2828 32774 4/12288/1 5/898/1 31 2 1 \ 1 2
-2838 32775 4/12288/1 5/899/1 31 2 1 \ 0 0
-2838 32776 4/12288/1 5/900/1 31 2 1 \ 1 4
-2838 32777 4/12288/1 5/901/1 31 2 1 \ 0 0
-2838 32778 4/12288/1 5/902/1 31 2 1 \ 1 2</screen>
- <para>The parameters are described below:</para>
+ </section>
+ <section>
+ <title>Configuring Timeouts in a Lustre File System</title>
+ <para>In a Lustre file system, RPC timeouts are set using an adaptive timeouts mechanism, which
+ is enabled by default. Servers track RPC completion times and then report back to clients
+ estimates for completion times for future RPCs. Clients use these estimates to set RPC
+ timeout values. If the processing of server requests slows down for any reason, the server
+ estimates for RPC completion increase, and clients then revise RPC timeout values to allow
+ more time for RPC completion.</para>
+ <para>If the RPCs queued on the server approach the RPC timeout specified by the client, to
+ avoid RPC timeouts and disconnect/reconnect cycles, the server sends an "early reply" to the
+ client, telling the client to allow more time. Conversely, as server processing speeds up, RPC
+ timeout values decrease, resulting in faster detection if the server becomes non-responsive
+ and quicker connection to the failover partner of the server.</para>
+ <section>
+ <title><indexterm>
+ <primary>proc</primary>
+ <secondary>configuring adaptive timeouts</secondary>
+ </indexterm><indexterm>
+ <primary>configuring</primary>
+ <secondary>adaptive timeouts</secondary>
+ </indexterm><indexterm>
+ <primary>proc</primary>
+ <secondary>adaptive timeouts</secondary>
+ </indexterm>Configuring Adaptive Timeouts</title>
+ <para>The adaptive timeout parameters in the table below can be set persistently system-wide
+ using <literal>lctl conf_param</literal> on the MGS. For example, the following command sets
+ the <literal>at_max</literal> value for all servers and clients associated with the file
+ system
+ <literal>testfs</literal>:<screen>lctl conf_param testfs.sys.at_max=1500</screen></para>
+ <note>
+ <para>Clients that access multiple Lustre file systems must use the same parameter values
+ for all file systems.</para>
+ </note>
<informaltable frame="all">
<tgroup cols="2">
- <colspec colname="c1" colwidth="50*"/>
- <colspec colname="c2" colwidth="50*"/>
+ <colspec colname="c1" colwidth="30*"/>
+ <colspec colname="c2" colwidth="80*"/>
<thead>
<row>
<entry>
<tbody>
<row>
<entry>
- <para> <emphasis role="bold">
- <literal>pid</literal>
- </emphasis></para>
- </entry>
- <entry>
- <para>Process that made the allocation.</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <emphasis role="bold">
- <literal>inode</literal>
- </emphasis></para>
- </entry>
- <entry>
- <para>inode number allocated blocks</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <emphasis role="bold">
- <literal>goal</literal>
- </emphasis></para>
- </entry>
- <entry>
- <para>Initial request that came to <literal>mballoc</literal> (group/block-in-group/number-of-blocks)</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <emphasis role="bold">
- <literal>result</literal>
- </emphasis></para>
- </entry>
- <entry>
- <para>What <literal>mballoc</literal> actually found for this request.</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <emphasis role="bold">
- <literal>found</literal>
- </emphasis></para>
- </entry>
- <entry>
- <para>Number of free chunks <literal>mballoc</literal> found and measured before the final decision.</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <emphasis role="bold">
- <literal>grps</literal>
- </emphasis></para>
+ <para>
+ <literal> at_min </literal></para>
</entry>
<entry>
- <para>Number of groups <literal>mballoc</literal> scanned to satisfy the request.</para>
+ <para>Minimum adaptive timeout (in seconds). The default value is 0. The
+ <literal>at_min</literal> parameter is the minimum processing time that a server
+ will report. Ideally, <literal>at_min</literal> should be set to its default
+ value. Clients base their timeouts on this value, but they do not use this value
+ directly. </para>
+ <para>If, for unknown reasons (usually due to temporary network outages), the
+ adaptive timeout value is too short and clients time out their RPCs, you can
+ increase the <literal>at_min</literal> value to compensate for this.</para>
</entry>
</row>
<row>
<entry>
- <para> <emphasis role="bold">
- <literal>cr</literal>
- </emphasis></para>
+ <para>
+ <literal> at_max </literal></para>
</entry>
<entry>
- <para>Stage at which <literal>mballoc</literal> found the result:</para>
- <para><emphasis role="bold">0</emphasis> - best in terms of resource allocation. The request was 1MB or larger and was satisfied directly via the kernel buddy allocator.</para>
- <para><emphasis role="bold">1</emphasis> - regular stage (good at resource consumption)</para>
- <para><emphasis role="bold">2</emphasis> - fs is quite fragmented (not that bad at resource consumption)</para>
- <para><emphasis role="bold">3</emphasis> - fs is very fragmented (worst at resource consumption)</para>
+ <para>Maximum adaptive timeout (in seconds). The <literal>at_max</literal> parameter
+ is an upper-limit on the service time estimate. If <literal>at_max</literal> is
+ reached, an RPC request times out.</para>
+ <para>Setting <literal>at_max</literal> to 0 causes adaptive timeouts to be disabled
+ and a fixed timeout method to be used instead (see <xref
+ xmlns:xlink="http://www.w3.org/1999/xlink" linkend="section_c24_nt5_dl"/></para>
+ <note>
+ <para>If slow hardware causes the service estimate to increase beyond the default
+ value of <literal>at_max</literal>, increase <literal>at_max</literal> to the
+ maximum time you are willing to wait for an RPC completion.</para>
+ </note>
</entry>
</row>
<row>
<entry>
- <para> <emphasis role="bold">
- <literal>queue</literal>
- </emphasis></para>
+ <para>
+ <literal> at_history </literal></para>
</entry>
<entry>
- <para>Total bytes in active/queued sends.</para>
+ <para>Time period (in seconds) within which adaptive timeouts remember the slowest
+ event that occurred. The default is 600.</para>
</entry>
</row>
<row>
<entry>
- <para> <emphasis role="bold">
- <literal>merge</literal>
- </emphasis></para>
+ <para>
+ <literal> at_early_margin </literal></para>
</entry>
<entry>
- <para>Whether the request hit the goal. This is good as extents code can now merge new blocks to existing extent, eliminating the need for extents tree growth.</para>
+ <para>Amount of time before the Lustre server sends an early reply (in seconds).
+ Default is 5.</para>
</entry>
</row>
<row>
<entry>
- <para> <emphasis role="bold">
- <literal>tail</literal>
- </emphasis></para>
+ <para>
+ <literal> at_extra </literal></para>
</entry>
<entry>
- <para>Number of blocks left free after the allocation breaks large free chunks.</para>
+ <para>Incremental amount of time that a server requests with each early reply (in
+ seconds). The server does not know how much time the RPC will take, so it asks for
+ a fixed value. The default is 30, which provides a balance between sending too
+ many early replies for the same RPC and overestimating the actual completion
+ time.</para>
+ <para>When a server finds a queued request about to time out and needs to send an
+ early reply out, the server adds the <literal>at_extra</literal> value. If the
+ time expires, the Lustre server drops the request, and the client enters recovery
+ status and reconnects to restore the connection to normal status.</para>
+ <para>If you see multiple early replies for the same RPC asking for 30-second
+ increases, change the <literal>at_extra</literal> value to a larger number to cut
+ down on early replies sent and, therefore, network load.</para>
</entry>
</row>
<row>
<entry>
- <para> <emphasis role="bold">
- <literal>broken</literal>
- </emphasis></para>
+ <para>
+ <literal> ldlm_enqueue_min </literal></para>
</entry>
<entry>
- <para>How large the broken chunk was.</para>
+ <para>Minimum lock enqueue time (in seconds). The default is 100. The time it takes
+ to enqueue a lock, <literal>ldlm_enqueue</literal>, is the maximum of the measured
+ enqueue estimate (influenced by <literal>at_min</literal> and
+ <literal>at_max</literal> parameters), multiplied by a weighting factor and the
+ value of <literal>ldlm_enqueue_min</literal>. </para>
+ <para>Lustre Distributed Lock Manager (LDLM) lock enqueues have a dedicated minimum
+ value for <literal>ldlm_enqueue_min</literal>. Lock enqueue timeouts increase as
+ the measured enqueue times increase (similar to adaptive timeouts).</para>
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
- <para>Most users are probably interested in found/cr. If cr is 0 1 and found is less than 100, then <literal>mballoc</literal> is doing quite well.</para>
- <para>Also, number-of-blocks-in-request (third number in the goal triple) can tell the number of blocks requested by the <literal>obdfilter</literal>. If the <literal>obdfilter</literal> is doing a lot of small requests (just few blocks), then either the client is processing input/output to a lot of small files, or something may be wrong with the client (because it is better if client sends large input/output requests). This can be investigated with the OSC <literal>rpc_stats</literal> or OST <literal>brw_stats</literal> mentioned above.</para>
- <para>Number of groups scanned (<literal>grps</literal> column) should be small. If it reaches a few dozen often, then either your disk file system is pretty fragmented or <literal>mballoc</literal> is doing something wrong in the group selection part.</para>
+ <section>
+ <title>Interpreting Adaptive Timeout Information</title>
+ <para>Adaptive timeout information can be obtained from the <literal>timeouts</literal>
+ files in <literal>/proc/fs/lustre/*/</literal> on each server and client using the
+ <literal>lctl</literal> command. To read information from a <literal>timeouts</literal>
+ file, enter a command similar to:</para>
+ <screen># lctl get_param -n ost.*.ost_io.timeouts
+service : cur 33 worst 34 (at 1193427052, 0d0h26m40s ago) 1 1 33 2</screen>
+ <para>In this example, the <literal>ost_io</literal> service on this node is currently
+ reporting an estimated RPC service time of 33 seconds. The worst RPC service time was 34
+ seconds, which occurred 26 minutes ago.</para>
+ <para>The output also provides a history of service times. Four "bins" of adaptive
+ timeout history are shown, with the maximum RPC time in each bin reported. In both the
+ 0-150s bin and the 150-300s bin, the maximum RPC time was 1. The 300-450s bin shows the
+ worst (maximum) RPC time at 33 seconds, and the 450-600s bin shows a maximum of RPC time
+ of 2 seconds. The estimated service time is the maximum value across the four bins (33
+ seconds in this example).</para>
+ <para>Service times (as reported by the servers) are also tracked in the client OBDs, as
+ shown in this example:</para>
+ <screen># lctl get_param osc.*.timeouts
+last reply : 1193428639, 0d0h00m00s ago
+network : cur 1 worst 2 (at 1193427053, 0d0h26m26s ago) 1 1 1 1
+portal 6 : cur 33 worst 34 (at 1193427052, 0d0h26m27s ago) 33 33 33 2
+portal 28 : cur 1 worst 1 (at 1193426141, 0d0h41m38s ago) 1 1 1 1
+portal 7 : cur 1 worst 1 (at 1193426141, 0d0h41m38s ago) 1 0 1 1
+portal 17 : cur 1 worst 1 (at 1193426177, 0d0h41m02s ago) 1 0 0 1
+</screen>
+ <para>In this example, portal 6, the <literal>ost_io</literal> service portal, shows the
+ history of service estimates reported by the portal.</para>
+ <para>Server statistic files also show the range of estimates including min, max, sum, and
+ sumsq. For example:</para>
+ <screen># lctl get_param mdt.*.mdt.stats
+...
+req_timeout 6 samples [sec] 1 10 15 105
+...
+</screen>
+ </section>
</section>
- <section remap="h3">
- <title><indexterm><primary>proc</primary><secondary>mballoc tunables</secondary></indexterm><literal>mballoc</literal> Tunables</title>
- <para>Lustre ldiskfs includes a multi-block allocation for ldiskfs to improve the efficiency of space allocation in the OST storage. Multi-block allocation adds the following features:</para>
- <itemizedlist>
+ <section xml:id="section_c24_nt5_dl">
+ <title>Setting Static Timeouts<indexterm>
+ <primary>proc</primary>
+ <secondary>static timeouts</secondary>
+ </indexterm></title>
+ <para>The Lustre software provides two sets of static (fixed) timeouts, LND timeouts and
+ Lustre timeouts, which are used when adaptive timeouts are not enabled.</para>
+ <para>
+ <itemizedlist>
+ <listitem>
+ <para><emphasis role="italic"><emphasis role="bold">LND timeouts</emphasis></emphasis> -
+ LND timeouts ensure that point-to-point communications across a network complete in a
+ finite time in the presence of failures, such as packages lost or broken connections.
+ LND timeout parameters are set for each individual LND.</para>
+ <para>LND timeouts are logged with the <literal>S_LND</literal> flag set. They are not
+ printed as console messages, so check the Lustre log for <literal>D_NETERROR</literal>
+ messages or enable printing of <literal>D_NETERROR</literal> messages to the console
+ using:<screen>lctl set_param printk=+neterror</screen></para>
+ <para>Congested routers can be a source of spurious LND timeouts. To avoid this
+ situation, increase the number of LNET router buffers to reduce back-pressure and/or
+ increase LND timeouts on all nodes on all connected networks. Also consider increasing
+ the total number of LNET router nodes in the system so that the aggregate router
+ bandwidth matches the aggregate server bandwidth.</para>
+ </listitem>
+ <listitem>
+ <para><emphasis role="italic"><emphasis role="bold">Lustre timeouts
+ </emphasis></emphasis>- Lustre timeouts ensure that Lustre RPCs complete in a finite
+ time in the presence of failures when adaptive timeouts are not enabled. Adaptive
+ timeouts are enabled by default. To disable adaptive timeouts at run time, set
+ <literal>at_max</literal> to 0 by running on the
+ MGS:<screen># lctl conf_param <replaceable>fsname</replaceable>.sys.at_max=0</screen></para>
+ <note>
+ <para>Changing the status of adaptive timeouts at runtime may cause a transient client
+ timeout, recovery, and reconnection.</para>
+ </note>
+ <para>Lustre timeouts are always printed as console messages. </para>
+ <para>If Lustre timeouts are not accompanied by LND timeouts, increase the Lustre
+ timeout on both servers and clients. Lustre timeouts are set using a command such as
+ the following:<screen># lctl set_param timeout=30</screen></para>
+ <para>Lustre timeout parameters are described in the table below.</para>
+ </listitem>
+ </itemizedlist>
+ <informaltable frame="all">
+ <tgroup cols="2">
+ <colspec colname="c1" colnum="1" colwidth="30*"/>
+ <colspec colname="c2" colnum="2" colwidth="70*"/>
+ <thead>
+ <row>
+ <entry>Parameter</entry>
+ <entry>Description</entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry><literal>timeout</literal></entry>
+ <entry>
+ <para>The time that a client waits for a server to complete an RPC (default 100s).
+ Servers wait half this time for a normal client RPC to complete and a quarter of
+ this time for a single bulk request (read or write of up to 4 MB) to complete.
+ The client pings recoverable targets (MDS and OSTs) at one quarter of the
+ timeout, and the server waits one and a half times the timeout before evicting a
+ client for being "stale."</para>
+ <para>Lustre client sends periodic 'ping' messages to servers with which
+ it has had no communication for the specified period of time. Any network
+ activity between a client and a server in the file system also serves as a
+ ping.</para>
+ </entry>
+ </row>
+ <row>
+ <entry><literal>ldlm_timeout</literal></entry>
+ <entry>
+ <para>The time that a server waits for a client to reply to an initial AST (lock
+ cancellation request). The default is 20s for an OST and 6s for an MDS. If the
+ client replies to the AST, the server will give it a normal timeout (half the
+ client timeout) to flush any dirty data and release the lock.</para>
+ </entry>
+ </row>
+ <row>
+ <entry><literal>fail_loc</literal></entry>
+ <entry>
+ <para>An internal debugging failure hook. The default value of
+ <literal>0</literal> means that no failure will be triggered or
+ injected.</para>
+ </entry>
+ </row>
+ <row>
+ <entry><literal>dump_on_timeout</literal></entry>
+ <entry>
+ <para>Triggers a dump of the Lustre debug log when a timeout occurs. The default
+ value of <literal>0</literal> (zero) means a dump of the Lustre debug log will
+ not be triggered.</para>
+ </entry>
+ </row>
+ <row>
+ <entry><literal>dump_on_eviction</literal></entry>
+ <entry>
+ <para>Triggers a dump of the Lustre debug log when an eviction occurs. The default
+ value of <literal>0</literal> (zero) means a dump of the Lustre debug log will
+ not be triggered. </para>
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ </para>
+ </section>
+ </section>
+ <section remap="h3">
+ <title><indexterm>
+ <primary>proc</primary>
+ <secondary>LNET</secondary>
+ </indexterm><indexterm>
+ <primary>LNET</primary>
+ <secondary>proc</secondary>
+ </indexterm>Monitoring LNET</title>
+ <para>LNET information is located in <literal>/proc/sys/lnet</literal> in these files:<itemizedlist>
<listitem>
- <para> Pre-allocation for single files (helps to resist fragmentation)</para>
+ <para><literal>peers</literal> - Shows all NIDs known to this node and provides
+ information on the queue state.</para>
+ <para>Example:</para>
+ <screen># lctl get_param peers
+nid refs state max rtr min tx min queue
+0@lo 1 ~rtr 0 0 0 0 0 0
+192.168.10.35@tcp 1 ~rtr 8 8 8 8 6 0
+192.168.10.36@tcp 1 ~rtr 8 8 8 8 6 0
+192.168.10.37@tcp 1 ~rtr 8 8 8 8 6 0</screen>
+ <para>The fields are explained in the table below:</para>
+ <informaltable frame="all">
+ <tgroup cols="2">
+ <colspec colname="c1" colwidth="30*"/>
+ <colspec colname="c2" colwidth="80*"/>
+ <thead>
+ <row>
+ <entry>
+ <para><emphasis role="bold">Field</emphasis></para>
+ </entry>
+ <entry>
+ <para><emphasis role="bold">Description</emphasis></para>
+ </entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>
+ <para>
+ <literal>refs</literal>
+ </para>
+ </entry>
+ <entry>
+ <para>A reference count. </para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal>state</literal>
+ </para>
+ </entry>
+ <entry>
+ <para>If the node is a router, indicates the state of the router. Possible
+ values are:</para>
+ <itemizedlist>
+ <listitem>
+ <para><literal>NA</literal> - Indicates the node is not a router.</para>
+ </listitem>
+ <listitem>
+ <para><literal>up/down</literal>- Indicates if the node (router) is up or
+ down.</para>
+ </listitem>
+ </itemizedlist>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal>max </literal></para>
+ </entry>
+ <entry>
+ <para>Maximum number of concurrent sends from this peer.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal>rtr </literal></para>
+ </entry>
+ <entry>
+ <para>Number of routing buffer credits.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal>min </literal></para>
+ </entry>
+ <entry>
+ <para>Minimum number of routing buffer credits seen.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal>tx </literal></para>
+ </entry>
+ <entry>
+ <para>Number of send credits.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal>min </literal></para>
+ </entry>
+ <entry>
+ <para>Minimum number of send credits seen.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal>queue </literal></para>
+ </entry>
+ <entry>
+ <para>Total bytes in active/queued sends.</para>
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ <para>Credits are initialized to allow a certain number of operations (in the example
+ above the table, eight as shown in the <literal>max</literal> column. LNET keeps track
+ of the minimum number of credits ever seen over time showing the peak congestion that
+ has occurred during the time monitored. Fewer available credits indicates a more
+ congested resource. </para>
+ <para>The number of credits currently in flight (number of transmit credits) is shown in
+ the <literal>tx</literal> column. The maximum number of send credits available is shown
+ in the <literal>max</literal> column and never changes. The number of router buffers
+ available for consumption by a peer is shown in the <literal>rtr</literal>
+ column.</para>
+ <para>Therefore, <literal>rtr</literal> – <literal>tx</literal> is the number of transmits
+ in flight. Typically, <literal>rtr == max</literal>, although a configuration can be set
+ such that <literal>max >= rtr</literal>. The ratio of routing buffer credits to send
+ credits (<literal>rtr/tx</literal>) that is less than <literal>max</literal> indicates
+ operations are in progress. If the ratio <literal>rtr/tx</literal> is greater than
+ <literal>max</literal>, operations are blocking.</para>
+ <para>LNET also limits concurrent sends and number of router buffers allocated to a single
+ peer so that no peer can occupy all these resources.</para>
</listitem>
<listitem>
- <para> Pre-allocation for a group of files (helps to pack small files into large, contiguous chunks)</para>
+ <para><literal>nis</literal> - Shows the current queue health on this node.</para>
+ <para>Example:</para>
+ <screen># lctl get_param nis
+nid refs peer max tx min
+0@lo 3 0 0 0 0
+192.168.10.34@tcp 4 8 256 256 252
+</screen>
+ <para> The fields are explained in the table below.</para>
+ <informaltable frame="all">
+ <tgroup cols="2">
+ <colspec colname="c1" colwidth="30*"/>
+ <colspec colname="c2" colwidth="80*"/>
+ <thead>
+ <row>
+ <entry>
+ <para><emphasis role="bold">Field</emphasis></para>
+ </entry>
+ <entry>
+ <para><emphasis role="bold">Description</emphasis></para>
+ </entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>
+ <para>
+ <literal> nid </literal></para>
+ </entry>
+ <entry>
+ <para>Network interface.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal> refs </literal></para>
+ </entry>
+ <entry>
+ <para>Internal reference counter.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal> peer </literal></para>
+ </entry>
+ <entry>
+ <para>Number of peer-to-peer send credits on this NID. Credits are used to size
+ buffer pools.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal> max </literal></para>
+ </entry>
+ <entry>
+ <para>Total number of send credits on this NID.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal> tx </literal></para>
+ </entry>
+ <entry>
+ <para>Current number of send credits available on this NID.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal> min </literal></para>
+ </entry>
+ <entry>
+ <para>Lowest number of send credits available on this NID.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal> queue </literal></para>
+ </entry>
+ <entry>
+ <para>Total bytes in active/queued sends.</para>
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ <para><emphasis role="bold"><emphasis role="italic">Analysis:</emphasis></emphasis></para>
+ <para>Subtracting <literal>max</literal> from <literal>tx</literal>
+ (<literal>max</literal> - <literal>tx</literal>) yields the number of sends currently
+ active. A large or increasing number of active sends may indicate a problem.</para>
</listitem>
+ </itemizedlist></para>
+ </section>
+ <section remap="h3">
+ <title><indexterm>
+ <primary>proc</primary>
+ <secondary>free space</secondary>
+ </indexterm>Allocating Free Space on OSTs</title>
+ <para>Free space is allocated using either a round-robin or a weighted algorithm. The allocation
+ method is determined by the maximum amount of free-space imbalance between the OSTs. When free
+ space is relatively balanced across OSTs, the faster round-robin allocator is used, which
+ maximizes network balancing. The weighted allocator is used when any two OSTs are out of
+ balance by more than a specified threshold.</para>
+ <para>Free space distribution can be tuned using these two <literal>/proc</literal>
+ tunables:</para>
+ <itemizedlist>
+ <listitem>
+ <para><literal>qos_threshold_rr</literal> - The threshold at which the allocation method
+ switches from round-robin to weighted is set in this file. The default is to switch to the
+ weighted algorithm when any two OSTs are out of balance by more than 17 percent.</para>
+ </listitem>
+ <listitem>
+ <para><literal>qos_prio_free</literal> - The weighting priority used by the weighted
+ allocator can be adjusted in this file. Increasing the value of
+ <literal>qos_prio_free</literal> puts more weighting on the amount of free space
+ available on each OST and less on how stripes are distributed across OSTs. The default
+ value is 91 percent. When the free space priority is set to 100, weighting is based
+ entirely on free space and location is no longer used by the striping algorthm.</para>
+ </listitem>
+ </itemizedlist>
+ <para>For more information about monitoring and managing free space, see <xref
+ xmlns:xlink="http://www.w3.org/1999/xlink" linkend="dbdoclet.50438209_10424"/>.</para>
+ </section>
+ <section remap="h3">
+ <title><indexterm>
+ <primary>proc</primary>
+ <secondary>locking</secondary>
+ </indexterm>Configuring Locking</title>
+ <para>The <literal>lru_size</literal> parameter is used to control the number of client-side
+ locks in an LRU cached locks queue. LRU size is dynamic, based on load to optimize the number
+ of locks available to nodes that have different workloads (e.g., login/build nodes vs. compute
+ nodes vs. backup nodes).</para>
+ <para>The total number of locks available is a function of the server RAM. The default limit is
+ 50 locks/1 MB of RAM. If memory pressure is too high, the LRU size is shrunk. The number of
+ locks on the server is limited to <emphasis role="italic">the number of OSTs per
+ server</emphasis> * <emphasis role="italic">the number of clients</emphasis> * <emphasis
+ role="italic">the value of the</emphasis>
+ <literal>lru_size</literal>
+ <emphasis role="italic">setting on the client</emphasis> as follows: </para>
+ <itemizedlist>
+ <listitem>
+ <para>To enable automatic LRU sizing, set the <literal>lru_size</literal> parameter to 0. In
+ this case, the <literal>lru_size</literal> parameter shows the current number of locks
+ being used on the export. LRU sizing is enabled by default.</para>
+ </listitem>
+ <listitem>
+ <para>To specify a maximum number of locks, set the <literal>lru_size</literal> parameter to
+ a value other than zero but, normally, less than 100 * <emphasis role="italic">number of
+ CPUs in client</emphasis>. It is recommended that you only increase the LRU size on a
+ few login nodes where users access the file system interactively.</para>
+ </listitem>
+ </itemizedlist>
+ <para>To clear the LRU on a single client, and, as a result, flush client cache without changing
+ the <literal>lru_size</literal> value, run:</para>
+ <screen>$ lctl set_param ldlm.namespaces.<replaceable>osc_name|mdc_name</replaceable>.lru_size=clear</screen>
+ <para>If the LRU size is set to be less than the number of existing unused locks, the unused
+ locks are canceled immediately. Use <literal>echo clear</literal> to cancel all locks without
+ changing the value.</para>
+ <note>
+ <para>The <literal>lru_size</literal> parameter can only be set temporarily using
+ <literal>lctl set_param</literal>; it cannot be set permanently.</para>
+ </note>
+ <para>To disable LRU sizing, on the Lustre clients, run:</para>
+ <screen>$ lctl set_param ldlm.namespaces.*osc*.lru_size=$((<replaceable>NR_CPU</replaceable>*100))</screen>
+ <para>Replace <literal><replaceable>NR_CPU</replaceable></literal> with the number of CPUs on
+ the node.</para>
+ <para>To determine the number of locks being granted, run:</para>
+ <screen>$ lctl get_param ldlm.namespaces.*.pool.limit</screen>
+ </section>
+ <section xml:id="dbdoclet.50438271_87260">
+ <title><indexterm>
+ <primary>proc</primary>
+ <secondary>thread counts</secondary>
+ </indexterm>Setting MDS and OSS Thread Counts</title>
+ <para>MDS and OSS thread counts tunable can be used to set the minimum and maximum thread counts
+ or get the current number of running threads for the services listed in the table
+ below.</para>
+ <informaltable frame="all">
+ <tgroup cols="2">
+ <colspec colname="c1" colwidth="50*"/>
+ <colspec colname="c2" colwidth="50*"/>
+ <tbody>
+ <row>
+ <entry>
+ <para>
+ <emphasis role="bold">Service</emphasis></para>
+ </entry>
+ <entry>
+ <para>
+ <emphasis role="bold">Description</emphasis></para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <literal> mdt.MDS.mds </literal>
+ </entry>
+ <entry>
+ <para>Main metadata operations service</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <literal> mdt.MDS.mds_readpage </literal>
+ </entry>
+ <entry>
+ <para>Metadata <literal>readdir</literal> service</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <literal> mdt.MDS.mds_setattr </literal>
+ </entry>
+ <entry>
+ <para>Metadata <literal>setattr/close</literal> operations service </para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <literal> ost.OSS.ost </literal>
+ </entry>
+ <entry>
+ <para>Main data operations service</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <literal> ost.OSS.ost_io </literal>
+ </entry>
+ <entry>
+ <para>Bulk data I/O services</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <literal> ost.OSS.ost_create </literal>
+ </entry>
+ <entry>
+ <para>OST object pre-creation service</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <literal> ldlm.services.ldlm_canceld </literal>
+ </entry>
+ <entry>
+ <para>DLM lock cancel service</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <literal> ldlm.services.ldlm_cbd </literal>
+ </entry>
+ <entry>
+ <para>DLM lock grant service</para>
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ <para>For each service, an entry as shown below is
+ created:<screen>/proc/fs/lustre/<replaceable>{service}</replaceable>/*/thread_<replaceable>{min,max,started}</replaceable></screen></para>
+ <para>To temporarily set this tunable, run:</para>
+ <screen># lctl <replaceable>{get,set}</replaceable>_param <replaceable>{service}</replaceable>.thread_<replaceable>{min,max,started}</replaceable> </screen>
+ <para>To permanently set this tunable, run:</para>
+ <screen># lctl conf_param <replaceable>{service}</replaceable>.thread_<replaceable>{min,max,started}</replaceable> </screen>
+ <para>The following examples show how to set thread counts and get the number of running threads
+ for the service <literal>ost_io</literal> using the tunable
+ <literal>{service}.thread_{min,max,started}</literal>.</para>
+ <itemizedlist>
+ <listitem>
+ <para>To get the number of running threads, run:</para>
+ <screen># lctl get_param ost.OSS.ost_io.threads_started
+ost.OSS.ost_io.threads_started=128</screen>
+ </listitem>
+ <listitem>
+ <para>To set the number of threads to the maximum value (512), run:</para>
+ <screen># lctl get_param ost.OSS.ost_io.threads_max
+ost.OSS.ost_io.threads_max=512</screen>
+ </listitem>
+ <listitem>
+ <para>To set the maximum thread count to 256 instead of 512 (to avoid overloading the
+ storage or for an array with requests), run:</para>
+ <screen># lctl set_param ost.OSS.ost_io.threads_max=256
+ost.OSS.ost_io.threads_max=256</screen>
+ </listitem>
+ <listitem>
+ <para> To check if the <literal>threads_max</literal> setting is active, run:</para>
+ <screen># lctl get_param ost.OSS.ost_io.threads_max
+ost.OSS.ost_io.threads_max=256</screen>
+ </listitem>
+ </itemizedlist>
+ <note>
+ <para>If the number of service threads is changed while the file system is running, the change
+ may not take effect until the file system is stopped and rest. If the number of service
+ threads in use exceeds the new <literal>threads_max</literal> value setting, service threads
+ that are already running will not be stopped.</para>
+ </note>
+ <para>See also <xref xmlns:xlink="http://www.w3.org/1999/xlink" linkend="lustretuning"/></para>
+ </section>
+ <section xml:id="dbdoclet.50438271_83523">
+ <title><indexterm>
+ <primary>proc</primary>
+ <secondary>debug</secondary>
+ </indexterm>Enabling and Interpreting Debugging Logs</title>
+ <para>By default, a detailed log of all operations is generated to aid in debugging. Flags that
+ control debugging are found in <literal>/proc/sys/lnet/debug</literal>. </para>
+ <para>The overhead of debugging can affect the performance of Lustre file system. Therefore, to
+ minimize the impact on performance, the debug level can be lowered, which affects the amount
+ of debugging information kept in the internal log buffer but does not alter the amount of
+ information to goes into syslog. You can raise the debug level when you need to collect logs
+ to debug problems. </para>
+ <para>The debugging mask can be set using "symbolic names". The symbolic format is
+ shown in the examples below.<itemizedlist>
<listitem>
- <para> Stream allocation (helps to decrease the seek rate)</para>
+ <para>To verify the debug level used, examine the <literal>sysctl</literal> that controls
+ debugging by running:</para>
+ <screen># sysctl lnet.debug
+lnet.debug = ioctl neterror warning error emerg ha config console</screen>
</listitem>
- </itemizedlist>
- <para>The following <literal>mballoc</literal> tunables are available:</para>
- <informaltable frame="all">
- <tgroup cols="2">
- <colspec colname="c1" colwidth="50*"/>
- <colspec colname="c2" colwidth="50*"/>
- <thead>
- <row>
- <entry>
- <para><emphasis role="bold">Field</emphasis></para>
- </entry>
- <entry>
- <para><emphasis role="bold">Description</emphasis></para>
- </entry>
- </row>
- </thead>
- <tbody>
- <row>
- <entry>
- <para> <literal>mb_max_to_scan</literal></para>
- </entry>
- <entry>
- <para>Maximum number of free chunks that <literal>mballoc</literal> finds before a final decision to avoid livelock.</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal>mb_min_to_scan</literal></para>
- </entry>
- <entry>
- <para>Minimum number of free chunks that <literal>mballoc</literal> searches before picking the best chunk for allocation. This is useful for a very small request, to resist fragmentation of big free chunks.</para>
- </entry>
- </row>
+ <listitem>
+ <para>To turn off debugging (except for network error debugging), run the following
+ command on all nodes concerned:</para>
+ <screen># sysctl -w lnet.debug="neterror"
+lnet.debug = neterror</screen>
+ </listitem>
+ </itemizedlist><itemizedlist>
+ <listitem>
+ <para>To turn off debugging completely, run the following command on all nodes
+ concerned:</para>
+ <screen># sysctl -w lnet.debug=0
+lnet.debug = 0</screen>
+ </listitem>
+ <listitem>
+ <para>To set an appropriate debug level for a production environment, run:</para>
+ <screen># sysctl -w lnet.debug="warning dlmtrace error emerg ha rpctrace vfstrace"
+lnet.debug = warning dlmtrace error emerg ha rpctrace vfstrace</screen>
+ <para>The flags shown in this example collect enough high-level information to aid
+ debugging, but they do not cause any serious performance impact.</para>
+ </listitem>
+ </itemizedlist><itemizedlist>
+ <listitem>
+ <para>To clear all flags and set new flags, run:</para>
+ <screen># sysctl -w lnet.debug="warning"
+lnet.debug = warning</screen>
+ </listitem>
+ </itemizedlist><itemizedlist>
+ <listitem>
+ <para>To add new flags to flags that have already been set, precede each one with a
+ "<literal>+</literal>":</para>
+ <screen># sysctl -w lnet.debug="+neterror +ha"
+lnet.debug = +neterror +ha
+# sysctl lnet.debug
+lnet.debug = neterror warning ha</screen>
+ </listitem>
+ <listitem>
+ <para>To remove individual flags, precede them with a
+ "<literal>-</literal>":</para>
+ <screen># sysctl -w lnet.debug="-ha"
+lnet.debug = -ha
+# sysctl lnet.debug
+lnet.debug = neterror warning</screen>
+ </listitem>
+ <listitem>
+ <para>To verify or change the debug level, run commands such as the following: :</para>
+ <screen># lctl get_param debug
+debug=
+neterror warning
+# lctl set_param debug=+ha
+# lctl get_param debug
+debug=
+neterror warning ha
+# lctl set_param debug=-warning
+# lctl get_param debug
+debug=
+neterror ha</screen>
+ </listitem>
+ </itemizedlist></para>
+ <para>Debugging parameters include:</para>
+ <itemizedlist>
+ <listitem>
+ <para><literal>subsystem_debug</literal> - Controls the debug logs for subsystems.</para>
+ </listitem>
+ <listitem>
+ <para><literal>debug_path</literal> - Indicates the location where the debug log is dumped
+ when triggered automatically or manually. The default path is
+ <literal>/tmp/lustre-log</literal>.</para>
+ </listitem>
+ </itemizedlist>
+ <para>These parameters are also set using:<screen>sysctl -w lnet.debug={value}</screen></para>
+ <para>Additional useful parameters: <itemizedlist>
+ <listitem>
+ <para><literal>panic_on_lbug</literal> - Causes ''panic'' to be called
+ when the Lustre software detects an internal problem (an <literal>LBUG</literal> log
+ entry); panic crashes the node. This is particularly useful when a kernel crash dump
+ utility is configured. The crash dump is triggered when the internal inconsistency is
+ detected by the Lustre software. </para>
+ </listitem>
+ <listitem>
+ <para><literal>upcall</literal> - Allows you to specify the path to the binary which will
+ be invoked when an <literal>LBUG</literal> log entry is encountered. This binary is
+ called with four parameters:</para>
+ <para> - The string ''<literal>LBUG</literal>''.</para>
+ <para> - The file where the <literal>LBUG</literal> occurred.</para>
+ <para> - The function name.</para>
+ <para> - The line number in the file</para>
+ </listitem>
+ </itemizedlist></para>
+ <section>
+ <title>Interpreting OST Statistics</title>
+ <note>
+ <para>See also <xref linkend="dbdoclet.50438219_84890"/> (<literal>llobdstat</literal>) and
+ <xref linkend="dbdoclet.50438273_80593"/> (<literal>collectl</literal>).</para>
+ </note>
+ <para>OST <literal>stats</literal> files can be used to provide statistics showing activity
+ for each OST. For example:</para>
+ <screen># lctl get_param osc.testfs-OST0000-osc.stats
+snapshot_time 1189732762.835363
+ost_create 1
+ost_get_info 1
+ost_connect 1
+ost_set_info 1
+obd_ping 212</screen>
+ <para>Use the <literal>llstat</literal> utility to monitor statistics over time.</para>
+ <para>To clear the statistics, use the <literal>-c</literal> option to
+ <literal>llstat</literal>. To specify how frequently the statistics should be reported (in
+ seconds), use the <literal>-i</literal> option. In the example below, the
+ <literal>-c</literal> option clears the statistics and <literal>-i10</literal> option
+ reports statistics every 10 seconds:</para>
+ <screen role="smaller">$ llstat -c -i10 /proc/fs/lustre/ost/OSS/ost_io/stats
+
+/usr/bin/llstat: STATS on 06/06/07
+ /proc/fs/lustre/ost/OSS/ost_io/ stats on 192.168.16.35@tcp
+snapshot_time 1181074093.276072
+
+/proc/fs/lustre/ost/OSS/ost_io/stats @ 1181074103.284895
+Name Cur. Cur. #
+ Count Rate Events Unit last min avg max stddev
+req_waittime 8 0 8 [usec] 2078 34 259.75 868 317.49
+req_qdepth 8 0 8 [reqs] 1 0 0.12 1 0.35
+req_active 8 0 8 [reqs] 11 1 1.38 2 0.52
+reqbuf_avail 8 0 8 [bufs] 511 63 63.88 64 0.35
+ost_write 8 0 8 [bytes] 169767 72914 212209.62 387579 91874.29
+
+/proc/fs/lustre/ost/OSS/ost_io/stats @ 1181074113.290180
+Name Cur. Cur. #
+ Count Rate Events Unit last min avg max stddev
+req_waittime 31 3 39 [usec] 30011 34 822.79 12245 2047.71
+req_qdepth 31 3 39 [reqs] 0 0 0.03 1 0.16
+req_active 31 3 39 [reqs] 58 1 1.77 3 0.74
+reqbuf_avail 31 3 39 [bufs] 1977 63 63.79 64 0.41
+ost_write 30 3 38 [bytes] 1028467 15019 315325.16 910694 197776.51
+
+/proc/fs/lustre/ost/OSS/ost_io/stats @ 1181074123.325560
+Name Cur. Cur. #
+ Count Rate Events Unit last min avg max stddev
+req_waittime 21 2 60 [usec] 14970 34 784.32 12245 1878.66
+req_qdepth 21 2 60 [reqs] 0 0 0.02 1 0.13
+req_active 21 2 60 [reqs] 33 1 1.70 3 0.70
+reqbuf_avail 21 2 60 [bufs] 1341 63 63.82 64 0.39
+ost_write 21 2 59 [bytes] 7648424 15019 332725.08 910694 180397.87
+</screen>
+ <para>The columns in this example are described in the table below.</para>
+ <informaltable frame="all">
+ <tgroup cols="2">
+ <colspec colname="c1" colwidth="50*"/>
+ <colspec colname="c2" colwidth="50*"/>
+ <thead>
+ <row>
+ <entry>
+ <para><emphasis role="bold">Parameter</emphasis></para>
+ </entry>
+ <entry>
+ <para><emphasis role="bold">Description</emphasis></para>
+ </entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry><literal>Name</literal></entry>
+ <entry>Name of the service event. See the tables below for descriptions of service
+ events that are tracked.</entry>
+ </row>
<row>
<entry>
- <para> <literal>mb_order2_req</literal></para>
+ <para>
+ <literal>Cur. Count </literal></para>
</entry>
<entry>
- <para>For requests equal to 2^N (where N >= <literal>order2_req</literal>), a very fast search via buddy structures is used.</para>
+ <para>Number of events of each type sent in the last interval.</para>
</entry>
</row>
<row>
<entry>
- <para> <literal>mb_small_req</literal></para>
+ <para>
+ <literal>Cur. Rate </literal></para>
</entry>
- <entry morerows="1">
- <para>All requests are divided into 3 categories:</para>
- <para>< small_req (packed together to form large, aggregated requests)</para>
- <para>< large_req (allocated mostly in linearly)</para>
- <para>> large_req (very large requests so the arm seek does not matter)</para>
- <para>The idea is that we try to pack small requests to form large requests, and then place all large requests (including compound from the small ones) close to one another, causing as few arm seeks as possible.</para>
+ <entry>
+ <para>Number of events per second in the last interval.</para>
</entry>
</row>
<row>
<entry>
- <para> <literal>mb_large_req</literal></para>
+ <para>
+ <literal> # Events </literal></para>
+ </entry>
+ <entry>
+ <para>Total number of such events since the events have been cleared.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal> Unit </literal></para>
+ </entry>
+ <entry>
+ <para>Unit of measurement for that statistic (microseconds, requests,
+ buffers).</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal> last </literal></para>
+ </entry>
+ <entry>
+ <para>Average rate of these events (in units/event) for the last interval during
+ which they arrived. For instance, in the above mentioned case of
+ <literal>ost_destroy</literal> it took an average of 736 microseconds per
+ destroy for the 400 object destroys in the previous 10 seconds.</para>
</entry>
</row>
<row>
<entry>
- <para> <literal>mb_prealloc_table</literal></para>
+ <para>
+ <literal> min </literal></para>
</entry>
<entry>
- <para>The amount of space to preallocate depends on the current file size. The idea is that for small files we do not need 1 MB preallocations and for large files, 1 MB preallocations are not large enough; it is better to preallocate 4 MB.</para>
+ <para>Minimum rate (in units/events) since the service started.</para>
</entry>
</row>
<row>
<entry>
- <para> <literal>mb_group_prealloc</literal></para>
+ <para>
+ <literal> avg </literal></para>
</entry>
<entry>
- <para>The amount of space (in kilobytes) preallocated for groups of small requests.</para>
+ <para>Average rate.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal> max </literal></para>
+ </entry>
+ <entry>
+ <para>Maximum rate.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para>
+ <literal> stddev </literal></para>
+ </entry>
+ <entry>
+ <para>Standard deviation (not measured in some cases)</para>
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
- </section>
- <section remap="h3">
- <title><indexterm><primary>proc</primary><secondary>locking</secondary></indexterm>Locking</title>
- <para><literal> ldlm.namespaces.<replaceable>osc_name|mdc_name</replaceable>.lru_size </literal></para>
- <para>The <literal>lru_size</literal> parameter is used to control the number of client-side locks in an LRU queue. LRU size is dynamic, based on load. This optimizes the number of locks available to nodes that have different workloads (e.g., login/build nodes vs. compute nodes vs. backup nodes).</para>
- <para>The total number of locks available is a function of the server's RAM. The default limit is 50 locks/1 MB of RAM. If there is too much memory pressure, then the LRU size is shrunk. The number of locks on the server is limited to <replaceable>targets_on_server</replaceable> * <replaceable>client_count</replaceable> * <replaceable>client_lru_size</replaceable>.</para>
- <itemizedlist>
- <listitem>
- <para>To enable automatic LRU sizing, set the <literal>lru_size</literal> parameter to 0. In this case, the <literal>lru_size</literal> parameter shows the current number of locks being used on the export. LRU sizing is enabled by default starting with Lustre 1.6.5.1.</para>
- </listitem>
- <listitem>
- <para>To specify a maximum number of locks, set the lru_size parameter to a value other than 0 (former numbers are okay, 100 * <replaceable>core_count</replaceable>). We recommend that you only increase the LRU size on a few login nodes where users access the file system interactively.</para>
- </listitem>
- </itemizedlist>
- <para>To clear the LRU on a single client, and as a result flush client cache, without changing the <literal>lru_size</literal> value:</para>
- <screen>$ lctl set_param ldlm.namespaces.<replaceable>osc_name|mdc_name</replaceable>.lru_size=clear</screen>
- <para>If you shrink the LRU size below the number of existing unused locks, then the unused locks are canceled immediately. Use echo clear to cancel all locks without changing the value.</para>
- <note>
- <para>Currently, the lru_size parameter can only be set temporarily with <literal>lctl set_param</literal>; it cannot be set permanently.</para>
- </note>
- <para>To disable LRU sizing, run this command on the Lustre clients:</para>
- <screen>$ lctl set_param ldlm.namespaces.*osc*.lru_size=$((NR_CPU*100))</screen>
- <para>Replace <literal>NR_CPU</literal> value with the number of CPUs on the node.</para>
- <para>To determine the number of locks being granted:</para>
- <screen>$ lctl get_param ldlm.namespaces.*.pool.limit</screen>
- </section>
- <section xml:id="dbdoclet.50438271_87260">
- <title><indexterm><primary>proc</primary><secondary>thread counts</secondary></indexterm>Setting MDS and OSS Thread Counts</title>
- <para>MDS and OSS thread counts (minimum and maximum) can be set via the <literal>{min,max}_thread_count tunable</literal>. For each service, a new <literal>/proc/fs/lustre/{service}/*/thread_{min,max,started}</literal> entry is created. The tunable, <literal>{service}.thread_{min,max,started}</literal>, can be used to set the minimum and maximum thread counts or get the current number of running threads for the following services.</para>
+ <para>Events common to all services are shown in the table below.</para>
<informaltable frame="all">
<tgroup cols="2">
<colspec colname="c1" colwidth="50*"/>
<colspec colname="c2" colwidth="50*"/>
- <tbody>
- <row>
- <entry>
- <para> <emphasis role="bold">Service</emphasis></para>
- </entry>
- <entry>
- <para> <emphasis role="bold">Description</emphasis></para>
- </entry>
- </row>
+ <thead>
<row>
<entry>
- <literal> mdt.MDS.mds </literal>
+ <para><emphasis role="bold">Parameter</emphasis></para>
</entry>
<entry>
- <para>normal metadata ops</para>
+ <para><emphasis role="bold">Description</emphasis></para>
</entry>
</row>
+ </thead>
+ <tbody>
<row>
<entry>
- <literal> mdt.MDS.mds_readpage </literal>
+ <para>
+ <literal> req_waittime </literal></para>
</entry>
<entry>
- <para>metadata readdir</para>
+ <para>Amount of time a request waited in the queue before being handled by an
+ available server thread.</para>
</entry>
</row>
<row>
<entry>
- <literal> mdt.MDS.mds_setattr </literal>
+ <para>
+ <literal> req_qdepth </literal></para>
</entry>
<entry>
- <para>metadata setattr</para>
+ <para>Number of requests waiting to be handled in the queue for this service.</para>
</entry>
</row>
<row>
<entry>
- <literal> ost.OSS.ost </literal>
+ <para>
+ <literal> req_active </literal></para>
</entry>
<entry>
- <para>normal data</para>
+ <para>Number of requests currently being handled.</para>
</entry>
</row>
<row>
<entry>
- <literal> ost.OSS.ost_io </literal>
+ <para>
+ <literal> reqbuf_avail </literal></para>
</entry>
<entry>
- <para>bulk data IO</para>
+ <para>Number of unsolicited lnet request buffers for this service.</para>
</entry>
</row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ <para>Some service-specific events of interest are described in the table below.</para>
+ <informaltable frame="all">
+ <tgroup cols="2">
+ <colspec colname="c1" colwidth="50*"/>
+ <colspec colname="c2" colwidth="50*"/>
+ <thead>
<row>
<entry>
- <literal> ost.OSS.ost_create </literal>
+ <para><emphasis role="bold">Parameter</emphasis></para>
</entry>
<entry>
- <para>OST object pre-creation service</para>
+ <para><emphasis role="bold">Description</emphasis></para>
</entry>
</row>
+ </thead>
+ <tbody>
<row>
<entry>
- <literal> ldlm.services.ldlm_canceld </literal>
+ <para>
+ <literal> ldlm_enqueue </literal></para>
</entry>
<entry>
- <para>DLM lock cancel</para>
+ <para>Time it takes to enqueue a lock (this includes file open on the MDS)</para>
</entry>
</row>
<row>
<entry>
- <literal> ldlm.services.ldlm_cbd </literal>
+ <para>
+ <literal> mds_reint </literal></para>
</entry>
<entry>
- <para>DLM lock grant</para>
+ <para>Time it takes to process an MDS modification record (includes
+ <literal>create</literal>, <literal>mkdir</literal>, <literal>unlink</literal>,
+ <literal>rename</literal> and <literal>setattr</literal>)</para>
</entry>
</row>
</tbody>
</tgroup>
</informaltable>
- <itemizedlist>
- <listitem>
- <para>To temporarily set this tunable, run:</para>
- <screen># lctl {get,set}_param {service}.thread_{min,max,started} </screen>
- </listitem>
- </itemizedlist>
- <itemizedlist>
- <listitem>
- <para>To permanently set this tunable, run:</para>
- <screen># lctl conf_param {service}.thread_{min,max,started} </screen>
- <para>The following examples show how to set thread counts and get the number of running threads for the ost_io service.</para>
- </listitem>
- </itemizedlist>
- <itemizedlist>
- <listitem>
- <para>To get the number of running threads, run:</para>
- <screen># lctl get_param ost.OSS.ost_io.threads_started</screen>
- <para>The command output will be similar to this:</para>
- <screen>ost.OSS.ost_io.threads_started=128</screen>
- </listitem>
- </itemizedlist>
- <itemizedlist>
- <listitem>
- <para>To set the maximum number of threads (512), run:</para>
- <screen># lctl get_param ost.OSS.ost_io.threads_max</screen>
- <para>The command output will be:</para>
- <screen>ost.OSS.ost_io.threads_max=512</screen>
- </listitem>
- </itemizedlist>
- <itemizedlist>
- <listitem>
- <para> To set the maximum thread count to 256 instead of 512 (to avoid overloading the storage or for an array with requests), run:</para>
- <screen># lctl set_param ost.OSS.ost_io.threads_max=256</screen>
- <para>The command output will be:</para>
- <screen>ost.OSS.ost_io.threads_max=256</screen>
- </listitem>
- </itemizedlist>
- <itemizedlist>
- <listitem>
- <para> To check if the new <literal>threads_max</literal> setting is active, run:</para>
- <screen># lctl get_param ost.OSS.ost_io.threads_max</screen>
- <para>The command output will be similar to this:</para>
- <screen>ost.OSS.ost_io.threads_max=256</screen>
- </listitem>
- </itemizedlist>
+ </section>
+ <section>
+ <title>Interpreting MDT Statistics</title>
<note>
- <para>Currently, the maximum thread count setting is advisory because Lustre does not reduce the number of service threads in use, even if that number exceeds the <literal>threads_max</literal> value. Lustre does not stop service threads once they are started.</para>
+ <para>See also <xref linkend="dbdoclet.50438219_84890"/> (<literal>llobdstat</literal>) and
+ <xref linkend="dbdoclet.50438273_80593"/> (<literal>collectl</literal>).</para>
</note>
- </section>
- </section>
- <section xml:id="dbdoclet.50438271_83523">
- <title><indexterm><primary>proc</primary><secondary>debug</secondary></indexterm>Debug</title>
- <para><literal> /proc/sys/lnet/debug </literal></para>
- <para>By default, Lustre generates a detailed log of all operations to aid in debugging. The level of debugging can affect the performance or speed you achieve with Lustre. Therefore, it is useful to reduce this overhead by turning down the debug level<footnote>
- <para>This controls the level of Lustre debugging kept in the internal log buffer. It does not alter the level of debugging that goes to syslog.</para>
- </footnote> to improve performance. Raise the debug level when you need to collect the logs for debugging problems. The debugging mask can be set with "symbolic names" instead of the numerical values that were used in prior releases. The new symbolic format is shown in the examples below.</para>
- <note>
- <para>All of the commands below must be run as root; note the <literal>#</literal> nomenclature.</para>
- </note>
- <para>To verify the debug level used by examining the <literal>sysctl</literal> that controls debugging, run:</para>
- <screen># sysctl lnet.debug
-lnet.debug = ioctl neterror warning error emerg ha config console</screen>
- <para>To turn off debugging (except for network error debugging), run this command on all concerned nodes:</para>
- <screen># sysctl -w lnet.debug="neterror"
-lnet.debug = neterror</screen>
- <para>To turn off debugging completely, run this command on all concerned nodes:</para>
- <screen># sysctl -w lnet.debug=0
-lnet.debug = 0</screen>
- <para>To set an appropriate debug level for a production environment, run:</para>
- <screen># sysctl -w lnet.debug="warning dlmtrace error emerg ha rpctrace vfstrace"
-lnet.debug = warning dlmtrace error emerg ha rpctrace vfstrace</screen>
- <para>The flags above collect enough high-level information to aid debugging, but they do not cause any serious performance impact.</para>
- <para>To clear all flags and set new ones, run:</para>
- <screen># sysctl -w lnet.debug="warning"
-lnet.debug = warning</screen>
- <para>To add new flags to existing ones, prefix them with a "<literal>+</literal>":</para>
- <screen># sysctl -w lnet.debug="+neterror +ha"
-lnet.debug = +neterror +ha
-# sysctl lnet.debug
-lnet.debug = neterror warning ha</screen>
- <para>To remove flags, prefix them with a "<literal>-</literal>":</para>
- <screen># sysctl -w lnet.debug="-ha"
-lnet.debug = -ha
-# sysctl lnet.debug
-lnet.debug = neterror warning</screen>
- <para>You can verify and change the debug level using the <literal>/proc</literal> interface in Lustre. To use the flags with <literal>/proc</literal>, run:</para>
- <screen># lctl get_param debug
-debug=
-neterror warning
-# lctl set_param debug=+ha
-# lctl get_param debug
-debug=
-neterror warning ha
-# lctl set_param debug=-warning
-# lctl get_param debug
-debug=
-neterror ha</screen>
- <para><literal> /proc/sys/lnet/subsystem_debug </literal></para>
- <para>This controls the debug logs for subsystems (see <literal>S_*</literal> definitions).</para>
- <para><literal> /proc/sys/lnet/debug_path </literal></para>
- <para>This indicates the location where debugging symbols should be stored for <literal>gdb</literal>. The default is set to <literal>/r/tmp/lustre-log-localhost.localdomain</literal>.</para>
- <para>These values can also be set via <literal>sysctl -w lnet.debug={value}</literal></para>
- <note>
- <para>The above entries only exist when Lustre has already been loaded.</para>
- </note>
- <para><literal> /proc/sys/lnet/panic_on_lbug </literal></para>
- <para>This causes Lustre to call ''panic'' when it detects an internal problem (an <literal>LBUG</literal>); panic crashes the node. This is particularly useful when a kernel crash dump utility is configured. The crash dump is triggered when the internal inconsistency is detected by Lustre.</para>
- <para><literal> /proc/sys/lnet/upcall </literal></para>
- <para>This allows you to specify the path to the binary which will be invoked when an <literal>LBUG</literal> is encountered. This binary is called with four parameters. The first one is the string ''<literal>LBUG</literal>''. The second one is the file where the <literal>LBUG</literal> occurred. The third one is the function name. The fourth one is the line number in the file.</para>
- <section remap="h3">
- <title>RPC Information for Other OBD Devices</title>
- <para>Some OBD devices maintain a count of the number of RPC events that they process. Sometimes these events are more specific to operations of the device, like llite, than actual raw RPC counts.</para>
- <screen>$ find /proc/fs/lustre/ -name stats
-/proc/fs/lustre/osc/lustre-OST0001-osc-ce63ca00/stats
-/proc/fs/lustre/osc/lustre-OST0000-osc-ce63ca00/stats
-/proc/fs/lustre/osc/lustre-OST0001-osc/stats
-/proc/fs/lustre/osc/lustre-OST0000-osc/stats
-/proc/fs/lustre/mdt/MDS/mds_readpage/stats
-/proc/fs/lustre/mdt/MDS/mds_setattr/stats
-/proc/fs/lustre/mdt/MDS/mds/stats
-/proc/fs/lustre/mds/lustre-MDT0000/exports/ab206805-0630-6647-8543-d24265c91a3d/stats
-/proc/fs/lustre/mds/lustre-MDT0000/exports/08ac6584-6c4a-3536-2c6d-b36cf9cbdaa0/stats
-/proc/fs/lustre/mds/lustre-MDT0000/stats
-/proc/fs/lustre/ldlm/services/ldlm_canceld/stats
-/proc/fs/lustre/ldlm/services/ldlm_cbd/stats
-/proc/fs/lustre/llite/lustre-ce63ca00/stats
-</screen>
- <section remap="h4">
- <title><indexterm><primary>proc</primary><secondary>statistics</secondary></indexterm>Interpreting OST Statistics</title>
- <note>
- <para>See also <xref linkend="dbdoclet.50438219_84890"/> (llobdstat) and <xref linkend="dbdoclet.50438273_80593"/> (CollectL).</para>
- </note>
- <para>The OST .../stats files can be used to track client statistics (client activity) for each OST. It is possible to get a periodic dump of values from these file (for example, every 10 seconds), that show the RPC rates (similar to iostat) by using the <literal>llstat.pl</literal> tool:</para>
- <screen># llstat /proc/fs/lustre/osc/lustre-OST0000-osc/stats
-/usr/bin/llstat: STATS on 09/14/07 /proc/fs/lustre/osc/lustre-OST0000-osc/stats on 192.168.10.34@tcp
-snapshot_time 1189732762.835363
-ost_create 1
-ost_get_info 1
-ost_connect 1
-ost_set_info 1
-obd_ping 212</screen>
- <para>To clear the statistics, give the <literal>-c</literal> option to <literal>llstat.pl</literal>. To specify how frequently the statistics should be cleared (in seconds), use an integer for the <literal>-i</literal> option. This is sample output with <literal>-c</literal> and <literal>-i10</literal> options used, providing statistics every 10s):</para>
- <screen>$ llstat -c -i10 /proc/fs/lustre/ost/OSS/ost_io/stats
-
-/usr/bin/llstat: STATS on 06/06/07 /proc/fs/lustre/ost/OSS/ost_io/ stats on 192.168.16.35@tcp
-snapshot_time 1181074093.276072
-
-/proc/fs/lustre/ost/OSS/ost_io/stats @ 1181074103.284895
-Name Cur.Count Cur.Rate #Events Unit \last min avg max stddev
-req_waittime 8 0 8 [usec] 2078\ 34 259.75 868 317.49
-req_qdepth 8 0 8 [reqs] 1\ 0 0.12 1 0.35
-req_active 8 0 8 [reqs] 11\ 1 1.38 2 0.52
-reqbuf_avail 8 0 8 [bufs] 511\ 63 63.88 64 0.35
-ost_write 8 0 8 [bytes] 1697677\ 72914 212209.62 387579 91874.29
-
-/proc/fs/lustre/ost/OSS/ost_io/stats @ 1181074113.290180
-Name Cur.Count Cur.Rate #Events Unit \last min avg max stddev
-req_waittime 31 3 39 [usec] 30011\ 34 822.79 12245 2047.71
-req_qdepth 31 3 39 [reqs] 0\ 0 0.03 1 0.16
-req_active 31 3 39 [reqs] 58\ 1 1.77 3 0.74
-reqbuf_avail 31 3 39 [bufs] 1977\ 63 63.79 64 0.41
-ost_write 30 3 38 [bytes] 10284679\ 15019 315325.16 910694 197776.51
-
-/proc/fs/lustre/ost/OSS/ost_io/stats @ 1181074123.325560
-Name Cur.Count Cur.Rate #Events Unit \last min avg max stddev
-req_waittime 21 2 60 [usec] 14970\ 34 784.32 12245 1878.66
-req_qdepth 21 2 60 [reqs] 0\ 0 0.02 1 0.13
-req_active 21 2 60 [reqs] 33\ 1 1.70 3 0.70
-reqbuf_avail 21 2 60 [bufs] 1341\ 63 63.82 64 0.39
-ost_write 21 2 59 [bytes] 7648424\ 15019 332725.08 910694 180397.87
-</screen>
- <para>Where:</para>
- <informaltable frame="all">
- <tgroup cols="2">
- <colspec colname="c1" colwidth="50*"/>
- <colspec colname="c2" colwidth="50*"/>
- <thead>
- <row>
- <entry>
- <para><emphasis role="bold">Parameter</emphasis></para>
- </entry>
- <entry>
- <para><emphasis role="bold">Description</emphasis></para>
- </entry>
- </row>
- </thead>
- <tbody>
- <row>
- <entry>
- <para> <literal> Cur. Count </literal></para>
- </entry>
- <entry>
- <para>Number of events of each type sent in the last interval (in this example, 10s)</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> Cur. Rate </literal></para>
- </entry>
- <entry>
- <para>Number of events per second in the last interval</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> #Events </literal></para>
- </entry>
- <entry>
- <para>Total number of such events since the system started</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> Unit </literal></para>
- </entry>
- <entry>
- <para>Unit of measurement for that statistic (microseconds, requests, buffers)</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> last </literal></para>
- </entry>
- <entry>
- <para>Average rate of these events (in units/event) for the last interval during which they arrived. For instance, in the above mentioned case of <literal>ost_destroy</literal> it took an average of 736 microseconds per destroy for the 400 object destroys in the previous 10 seconds.</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> min </literal></para>
- </entry>
- <entry>
- <para>Minimum rate (in units/events) since the service started</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> avg </literal></para>
- </entry>
- <entry>
- <para>Average rate</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> max </literal></para>
- </entry>
- <entry>
- <para>Maximum rate</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> stddev </literal></para>
- </entry>
- <entry>
- <para>Standard deviation (not measured in all cases)</para>
- </entry>
- </row>
- </tbody>
- </tgroup>
- </informaltable>
- <para>The events common to all services are:</para>
- <informaltable frame="all">
- <tgroup cols="2">
- <colspec colname="c1" colwidth="50*"/>
- <colspec colname="c2" colwidth="50*"/>
- <thead>
- <row>
- <entry>
- <para><emphasis role="bold">Parameter</emphasis></para>
- </entry>
- <entry>
- <para><emphasis role="bold">Description</emphasis></para>
- </entry>
- </row>
- </thead>
- <tbody>
- <row>
- <entry>
- <para> <literal> req_waittime </literal></para>
- </entry>
- <entry>
- <para>Amount of time a request waited in the queue before being handled by an available server thread.</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> req_qdepth </literal></para>
- </entry>
- <entry>
- <para>Number of requests waiting to be handled in the queue for this service.</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> req_active </literal></para>
- </entry>
- <entry>
- <para>Number of requests currently being handled.</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> reqbuf_avail </literal></para>
- </entry>
- <entry>
- <para>Number of unsolicited lnet request buffers for this service.</para>
- </entry>
- </row>
- </tbody>
- </tgroup>
- </informaltable>
- <para>Some service-specific events of interest are:</para>
- <informaltable frame="all">
- <tgroup cols="2">
- <colspec colname="c1" colwidth="50*"/>
- <colspec colname="c2" colwidth="50*"/>
- <thead>
- <row>
- <entry>
- <para><emphasis role="bold">Parameter</emphasis></para>
- </entry>
- <entry>
- <para><emphasis role="bold">Description</emphasis></para>
- </entry>
- </row>
- </thead>
- <tbody>
- <row>
- <entry>
- <para> <literal> ldlm_enqueue </literal></para>
- </entry>
- <entry>
- <para>Time it takes to enqueue a lock (this includes file open on the MDS)</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal> mds_reint </literal></para>
- </entry>
- <entry>
- <para>Time it takes to process an MDS modification record (includes create, <literal>mkdir</literal>, <literal>unlink</literal>, <literal>rename</literal> and <literal>setattr</literal>)</para>
- </entry>
- </row>
- </tbody>
- </tgroup>
- </informaltable>
- </section>
- <section remap="h4">
- <title><indexterm><primary>proc</primary><secondary>statistics</secondary></indexterm>Interpreting MDT Statistics</title>
- <note>
- <para>See also <xref linkend="dbdoclet.50438219_84890"/> (llobdstat) and <xref linkend="dbdoclet.50438273_80593"/> (CollectL).</para>
- </note>
- <para>The MDT .../stats files can be used to track MDT statistics for the MDS. Here is sample output for an MDT stats file:</para>
- <screen># cat /proc/fs/lustre/mds/*-MDT0000/stats
-snapshot_time 1244832003.676892 secs.usecs
-open 2 samples [reqs]
-close 1 samples [reqs]
-getxattr 3 samples [reqs]
-process_config 1 samples [reqs]
-connect 2 samples [reqs]
-disconnect 2 samples [reqs]
-statfs 3 samples [reqs]
-setattr 1 samples [reqs]
-getattr 3 samples [reqs]
-llog_init 6 samples [reqs]
-notify 16 samples [reqs]</screen>
- </section>
+ <para>MDT <literal>stats</literal> files can be used to track MDT statistics for the MDS. The
+ example below shows sample output from an MDT <literal>stats</literal> file.</para>
+ <screen># lctl get_param mds.*-MDT0000.stats
+snapshot_time 1244832003.676892 secs.usecs
+open 2 samples [reqs]
+close 1 samples [reqs]
+getxattr 3 samples [reqs]
+process_config 1 samples [reqs]
+connect 2 samples [reqs]
+disconnect 2 samples [reqs]
+statfs 3 samples [reqs]
+setattr 1 samples [reqs]
+getattr 3 samples [reqs]
+llog_init 6 samples [reqs]
+notify 16 samples [reqs]</screen>
</section>
</section>
</chapter>
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