<?xml version='1.0' encoding='UTF-8'?>
-<!-- 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="settinglustreproperties">
+<chapter xmlns="http://docbook.org/ns/docbook"
+ xmlns:xl="http://www.w3.org/1999/xlink" version="5.0" xml:lang="en-US"
+ xml:id="settinglustreproperties">
<title xml:id="settinglustreproperties.title">Setting Lustre Properties in a C Program (<literal>llapi</literal>)</title>
<para>This chapter describes the <literal>llapi</literal> library of commands used for setting Lustre file properties within a C program running in a cluster environment, such as a data processing or MPI application. The commands described in this chapter are:</para>
<itemizedlist>
<listitem>
- <para><xref linkend="dbdoclet.50438215_30970"/></para>
+ <para><xref linkend="llapi_file_create"/></para>
</listitem>
<listitem>
- <para><xref linkend="dbdoclet.50438215_50149"/></para>
+ <para><xref linkend="llapi_file_get_stripe"/></para>
</listitem>
<listitem>
- <para><xref linkend="dbdoclet.50438215_86607"/></para>
+ <para><xref linkend="llapi_file_open"/></para>
</listitem>
<listitem>
- <para><xref linkend="dbdoclet.50438215_12433"/></para>
+ <para><xref linkend="llapi_quotactl"/></para>
</listitem>
<listitem>
- <para><xref linkend="dbdoclet.50438215_15718"/></para>
+ <para><xref linkend="llapi_path2fid"/></para>
</listitem>
</itemizedlist>
<note>
<para>Lustre programming interface man pages are found in the <literal>lustre/doc</literal> folder.</para>
</note>
- <section xml:id="dbdoclet.50438215_30970">
+ <section xml:id="llapi_file_create">
<title>
<literal>llapi_file_create</literal>
</title>
</section>
<section remap="h5">
<title>Description</title>
- <para>The <literal>llapi_file_create()</literal> function sets a file descriptor's Lustre striping information. The file descriptor is then accessed with <literal>open()</literal>.</para>
+ <para>The <literal>llapi_file_create()</literal> function sets a file descriptor's Lustre
+ file system striping information. The file descriptor is then accessed with
+ <literal>open()</literal>.</para>
<informaltable frame="all">
<tgroup cols="2">
<colspec colname="c1" colwidth="50*"/>
}</screen>
</section>
</section>
- <section xml:id="dbdoclet.50438215_50149">
+ <section xml:id="llapi_file_get_stripe">
<title>llapi_file_get_stripe</title>
<para>Use <literal>llapi_file_get_stripe</literal> to get striping information for a file or directory on a Lustre file system.</para>
<section remap="h5">
<para> <literal>lmm_pattern</literal></para>
</entry>
<entry>
- <para>Holds the striping pattern. Only <literal>LOV_PATTERN_RAID0</literal> is possible in this Lustre version.</para>
+ <para>Holds the striping pattern. Only <literal>LOV_PATTERN_RAID0</literal> is
+ possible in this Lustre software release.</para>
</entry>
</row>
<row>
</programlisting>
</section>
</section>
- <section xml:id="dbdoclet.50438215_86607">
+ <section xml:id="llapi_file_open">
<title>
<literal>llapi_file_open</literal>
</title>
- <para>The <literal>llapi_file_open</literal> command opens (or creates) a file or device on a Lustre filesystem.</para>
+ <para>The <literal>llapi_file_open</literal> command opens (or creates) a file or device on a
+ Lustre file system.</para>
<section remap="h5">
<title>Synopsis</title>
<screen>#include <lustre/lustreapi.h>
<section remap="h5">
<title>Description</title>
<para>The <literal>llapi_file_create()</literal> call is equivalent to the <literal>llapi_file_open</literal> call with <emphasis>flags</emphasis> equal to <literal>O_CREAT|O_WRONLY</literal> and <emphasis>mode</emphasis> equal to <literal>0644</literal>, followed by file close.</para>
- <para><literal>llapi_file_open()</literal> opens a file with a given name on a Lustre filesystem.</para>
+ <para><literal>llapi_file_open()</literal> opens a file with a given name on a Lustre file
+ system.</para>
<informaltable frame="all">
<tgroup cols="2">
<colspec colname="c1" colwidth="50*"/>
<para> <literal>stripe_pattern</literal></para>
</entry>
<entry>
- <para>Specifies the striping pattern. In this version of Lustre, only <literal>LOV_PATTERN_RAID0</literal> is available. The default value is 0.</para>
+ <para>Specifies the striping pattern. In this release of the Lustre software, only
+ <literal>LOV_PATTERN_RAID0</literal> is available. The default value is
+ 0.</para>
</entry>
</row>
</tbody>
<para> <literal>ENOTTY</literal></para>
</entry>
<entry>
- <para> <literal>name</literal> may not point to a Lustre filesystem.</para>
+ <para>
+ <literal>name</literal> may not point to a Lustre file system.</para>
</entry>
</row>
</tbody>
</programlisting>
</section>
</section>
- <section xml:id="dbdoclet.50438215_12433">
+ <section xml:id="llapi_quotactl">
<title>
<literal>llapi_quotactl</literal>
</title>
<tbody>
<row>
<entry>
- <para> <literal>LUSTRE_Q_QUOTAON</literal></para>
- </entry>
- <entry>
- <para>Turns on quotas for a Lustre file system. Deprecated as of 2.4.0. <emphasis>qc_type</emphasis> is <literal>USRQUOTA</literal>, <literal>GRPQUOTA</literal> or <literal>UGQUOTA</literal> (both user and group quota). The quota files must exist. They are normally created with the <literal>llapi_quotacheck</literal> call. This call is restricted to the super user privilege. As of 2.4.0, quota is now enabled on a per-filesystem basis via <literal>lctl conf_param</literal> (see <xref linkend="enabling_disk_quotas"/>) on the MGS node and quotacheck isn't needed any more.</para>
- </entry>
- </row>
- <row>
- <entry>
- <para> <literal>LUSTRE_Q_QUOTAOFF</literal></para>
- </entry>
- <entry>
- <para>Turns off quotas for a Lustre file system. Deprecated as of 2.4.0. <emphasis>qc_type</emphasis> is <literal>USRQUOTA</literal>, <literal>GRPQUOTA</literal> or <literal>UGQUOTA</literal> (both user and group quota). This call is restricted to the super user privilege. As of 2.4.0, quota is disabled via <literal>lctl conf_param</literal> (see <xref linkend="enabling_disk_quotas"/>).</para>
- </entry>
- </row>
- <row>
- <entry>
<para> <literal>LUSTRE_Q_GETQUOTA</literal></para>
</entry>
<entry>
<para> <literal>LUSTRE_Q_GETINFO</literal></para>
</entry>
<entry>
- <para>Gets information about quotas. <emphasis>qc_type</emphasis> is either <literal>USRQUOTA</literal> or <literal>GRPQUOTA</literal>. On return, <emphasis>dqi_igrace</emphasis> is inode grace time (in seconds), <emphasis>dqi_bgrace</emphasis> is block grace time (in seconds), <emphasis>dqi_flags</emphasis> is not used by the current Lustre version.</para>
+ <para>Gets information about quotas. <emphasis>qc_type</emphasis> is either
+ <literal>USRQUOTA</literal> or <literal>GRPQUOTA</literal>. On return,
+ <emphasis>dqi_igrace</emphasis> is inode grace time (in seconds),
+ <emphasis>dqi_bgrace</emphasis> is block grace time (in seconds),
+ <emphasis>dqi_flags</emphasis> is not used by the current release of the Lustre
+ software.</para>
</entry>
</row>
<row>
<para> <literal>LUSTRE_Q_SETINFO</literal></para>
</entry>
<entry>
- <para>Sets quota information (like grace times). <emphasis>qc_type</emphasis> is either <literal>USRQUOTA</literal> or <literal>GRPQUOTA</literal>. <emphasis>dqi_igrace</emphasis> is inode grace time (in seconds), <emphasis>dqi_bgrace</emphasis> is block grace time (in seconds), <emphasis>dqi_flags</emphasis> is not used by the current Lustre version and must be zeroed.</para>
+ <para>Sets quota information (like grace times). <emphasis>qc_type</emphasis> is
+ either <literal>USRQUOTA</literal> or <literal>GRPQUOTA</literal>.
+ <emphasis>dqi_igrace</emphasis> is inode grace time (in seconds),
+ <emphasis>dqi_bgrace</emphasis> is block grace time (in seconds),
+ <emphasis>dqi_flags</emphasis> is not used by the current release of the Lustre
+ software and must be zeroed.</para>
</entry>
</row>
</tbody>
</row>
<row>
<entry>
- <para> <literal>EBUSY</literal></para>
- </entry>
- <entry>
- <para>Cannot process during quotacheck.</para>
- </entry>
- </row>
- <row>
- <entry>
<para> <literal>ENOENT</literal></para>
</entry>
<entry>
</informaltable>
</section>
</section>
- <section xml:id="dbdoclet.50438215_15718">
+ <section xml:id="llapi_path2fid">
<title>
<literal>llapi_path2fid</literal>
</title>
<para>non-zero value On failure</para>
</section>
</section>
- <section xml:id="dbdoclet.50438215_marker-1297700">
+ <section condition="l29">
+ <title>
+ <literal>llapi_ladvise</literal>
+ </title>
+ <para>Use <literal>llapi_ladvise</literal> to give IO advice/hints on a
+ Lustre file to the server.</para>
+ <section remap="h5">
+ <title>Synopsis</title>
+ <screen>
+#include <lustre/lustreapi.h>
+int llapi_ladvise(int fd, unsigned long long flags,
+ int num_advise, struct llapi_lu_ladvise *ladvise);
+
+struct llapi_lu_ladvise {
+ __u16 lla_advice; /* advice type */
+ __u16 lla_value1; /* values for different advice types */
+ __u32 lla_value2;
+ __u64 lla_start; /* first byte of extent for advice */
+ __u64 lla_end; /* last byte of extent for advice */
+ __u32 lla_value3;
+ __u32 lla_value4;
+};
+ </screen>
+ </section>
+ <section remap="h5">
+ <title>Description</title>
+ <para>The <literal>llapi_ladvise</literal> function passes an array of
+ <emphasis>num_advise</emphasis> I/O hints (up to a maximum of
+ <emphasis>LAH_COUNT_MAX</emphasis> items) in ladvise for the file
+ descriptor <emphasis>fd</emphasis> from an application to one or more
+ Lustre servers. Optionally, <emphasis>flags</emphasis> can modify how
+ the advice will be processed via bitwise-or'd values:</para>
+ <itemizedlist>
+ <listitem>
+ <para><literal>LF_ASYNC</literal>: Clients return to userspace
+ immediately after submitting ladvise RPCs, leaving server threads to
+ handle the advices asynchronously.</para>
+ </listitem>
+ <listitem>
+ <para><literal>LF_UNSET</literal>: Unset/clear a previous advice
+ (Currently only supports LU_ADVISE_LOCKNOEXPAND).</para>
+ </listitem>
+ </itemizedlist>
+ <para>Each of the <emphasis>ladvise</emphasis> elements is an
+ <emphasis>llapi_lu_ladvise</emphasis> structure, which contains the
+ following fields:
+ <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>lla_ladvice</literal></para>
+ </entry>
+ <entry>
+ <para>Specifies the advice for the given file range, currently
+ one of:</para>
+ <para><literal>LU_LADVISE_WILLREAD</literal>: Prefetch data
+ into server cache using optimum I/O size for the server.</para>
+ <para><literal>LU_LADVISE_DONTNEED</literal>: Clean cached data
+ for the specified file range(s) on the server.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para> <literal>lla_start</literal></para>
+ </entry>
+ <entry>
+ <para>The offset in bytes for the start of this advice.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para> <literal>lla_end</literal></para>
+ </entry>
+ <entry>
+ <para>The offset in bytes (non-inclusive) for the end of this
+ advice.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para> <literal>lla_value1</literal></para>
+ <para> <literal>lla_value2</literal></para>
+ <para> <literal>lla_value3</literal></para>
+ <para> <literal>lla_value4</literal></para>
+ </entry>
+ <entry>
+ <para>Additional arguments for future advice types and
+ should be set to zero if not explicitly required for a given
+ advice type. Advice-specific names for these fields
+ follow.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para> <literal>lla_lockahead_mode</literal></para>
+ </entry>
+ <entry>
+ <para>When using LU_ADVISE_LOCKAHEAD, the 'lla_value1' field
+ is used to communicate the requested lock mode, and can be
+ referred to as lla_lockahead_mode.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para> <literal>lla_peradvice_flags</literal></para>
+ </entry>
+ <entry>
+ <para>When using advices which support them, the 'lla_value2'
+ field is used to communicate per-advice flags and can be
+ referred to as 'lla_peradvice_flags'. Both LF_ASYNC and
+ LF_UNSET are supported as peradvice flags.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para> <literal>lla_lockahead_result</literal></para>
+ </entry>
+ <entry>
+ <para>When using LU_ADVISE_LOCKAHEAD, the 'lla_value3' field
+ is used to communicate the result of the request, and can be
+ referred to as lla_lockahead_result.</para>
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ </para>
+ <para><literal>llapi_ladvise()</literal> forwards the advice to Lustre
+ servers without guaranteeing how and when servers will react to the
+ advice. Actions may or may not be triggered when the advices are
+ received, depending on the type of the advice as well as the real-time
+ decision of the affected server-side components.
+ </para>
+ <para> A typical usage of <literal>llapi_ladvise()</literal> is to
+ enable applications and users (via <literal>lfs ladvise</literal>)
+ with external knowledge about application I/O patterns to intervene in
+ server-side I/O handling. For example, if a group of different clients
+ are doing small random reads of a file, prefetching pages into OSS
+ cache with big linear reads before the random IO is an overall net
+ benefit. Fetching that data into each client cache with
+ <emphasis>fadvise()</emphasis> may not be beneficial, due to much more
+ data being sent to the clients.
+ </para>
+ <para>
+ LU_LADVISE_LOCKAHEAD merits a special comment. While it is possible
+ and encouraged to use it directly in your application to avoid lock
+ contention (primarily for writing to a single file from multiple
+ clients), it will also be available in the MPI-I/O / MPICH library
+ from ANL for use with the i/o aggregation mode of that library. This
+ is intended (eventually) to be the primary way this feature is used.
+ </para>
+ <para>
+ At the time of writing, this support is proposed as a patch but is
+ not yet merged in to the public ANL code base. Users are encouraged
+ to check their MPICH documentation and/or check with their library
+ provider about support.
+ </para>
+ <para>While conceptually similar to the
+ <emphasis>posix_fadvise</emphasis> and Linux
+ <emphasis>fadvise</emphasis> system calls, the main difference of
+ <literal>llapi_ladvise()</literal> is that
+ <emphasis>fadvise() / posix_fadvise()</emphasis> are client side
+ mechanisms that do not pass advice to the filesystem, while
+ <literal>llapi_ladvise()</literal> sends advice or hints to one or
+ more Lustre servers on which the file is stored. In some cases it may
+ be desirable to use both interfaces.
+ </para>
+ </section>
+ <section remap="h5">
+ <title>Return Values</title>
+ <para><literal>llapi_ladvise</literal> returns:</para>
+ <para><literal>0</literal> On success</para>
+ <para><literal>-1</literal> if an error occurred (in which case, errno
+ is set appropriately).</para>
+ </section>
+ <section remap="h5">
+ <title>Errors</title>
+ <para>
+ <informaltable frame="all">
+ <tgroup cols="2">
+ <colspec colname="c1" colwidth="50*"/>
+ <colspec colname="c2" colwidth="50*"/>
+ <thead>
+ <row>
+ <entry>
+ <para><emphasis role="bold">Error</emphasis></para>
+ </entry>
+ <entry>
+ <para><emphasis role="bold">Description</emphasis></para>
+ </entry>
+ </row>
+ </thead>
+ <tbody>
+ <row>
+ <entry>
+ <para> <literal>ENOMEM</literal></para>
+ </entry>
+ <entry>
+ <para>Insufficient memory to complete operation.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para> <literal>EINVAL</literal></para>
+ </entry>
+ <entry>
+ <para>One or more invalid arguments are given.</para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para> <literal>EFAULT</literal></para>
+ </entry>
+ <entry>
+ <para>Memory region pointed by
+ <literal>ladvise</literal> is not properly mapped.
+ </para>
+ </entry>
+ </row>
+ <row>
+ <entry>
+ <para> <literal>ENOTSUPP</literal></para>
+ </entry>
+ <entry>
+ <para>Advice type is not supported.</para>
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ </para>
+ </section>
+ </section>
+ <section xml:id="example_using_llapi">
<title>Example Using the <literal>llapi</literal> Library</title>
- <para>Use <literal>llapi_file_create</literal> to set Lustre properties for a new file. For a synopsis and description of llapi_file_create and examples of how to use it, see <xref linkend="configurationfilesmoduleparameters"/>.</para>
+ <para>Use <literal>llapi_file_create</literal> to set Lustre software properties for a new file.
+ For a synopsis and description of <literal>llapi_file_create</literal> and examples of how to
+ use it, see <xref linkend="configurationfilesmoduleparameters"/>.</para>
<para>You can set striping from inside programs like <literal>ioctl</literal>. To compile the sample program, you need to install the Lustre client source RPM.</para>
<para><emphasis role="bold">A simple C program to demonstrate striping API - libtest.c</emphasis></para>
<programlisting>
<itemizedlist>
<listitem>
<para>
- <xref linkend="dbdoclet.50438215_30970"/>
+ <xref linkend="llapi_file_create"/>
</para>
</listitem>
<listitem>
<para>
- <xref linkend="dbdoclet.50438215_50149"/>
+ <xref linkend="llapi_file_get_stripe"/>
</para>
</listitem>
<listitem>
<para>
- <xref linkend="dbdoclet.50438215_86607"/>
+ <xref linkend="llapi_file_open"/>
</para>
</listitem>
<listitem>
<para>
- <xref linkend="dbdoclet.50438215_12433"/>
+ <xref linkend="llapi_quotactl"/>
</para>
</listitem>
</itemizedlist>
</section>
</section>
</chapter>
+<!--
+ vim:expandtab:shiftwidth=2:tabstop=8:
+ -->
git://git.whamcloud.com / doc / manual.git / blobdiff