.br
.SH DESCRIPTION
Give file access advices or hints to Lustre server side, usually OSS. This lfs
-utility is simlar to Linux fadvise() system call, except it can forward the
-advices from Lustre clients to servers.
+command is simlar to the Linux
+.BR fadvise64 (2)
+system call and
+.BR posix_fadvise (2),
+except it can forward the hints from Lustre clients to remote servers.
.SH OPTIONS
.TP
\fB\-a\fR, \fB\-\-advice\fR=\fIADVICE\fR
same time as the -e option.
.SH NOTE
.PP
-Typically, the "lfs ladvise" forwards the advice to Lustre servers without
-guaranteeing what and when servers will react to the advice. Actions may or
-may not triggered when the advices are recieved, depending on the type of the
-advice as well as the real-time decision of the affected server-side
-components.
+Typically,
+.B lfs ladvise
+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 recieved, depending on the type of
+the advice, whether the backing filesystem type supports that advice, as well
+as the real-time decision of the affected server-side components.
A typical usage of ladvise is to enable applications and users with external
knowledge to intervene in server-side cache management. For example, if a
-bunch of different clients are doing small random reads of a file, prefetching
+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 a net
benefit. Fetching that data into each client cache with fadvise() may not
-be, due to much more data being sent to the client.
+be a benefit if any individual client only reads a subset of the file.
The main difference between Linux fadvise() system call and ladvise is that
fadvise() is only a client side mechanism that does not pass the advice to the
.SH EXAMPLES
.TP
-.B $ lfs ladvise -a willread -s 0 -e 1048576000 /mnt/lustre/file1
+.B $ lfs ladvise -a willread -s 0 -e 1024M /mnt/lustre/file1
This gives the OST(s) holding the first 1GB of \fB/mnt/lustre/file1\fR a hint
-that the first 1GB of the file will be read soon.
+that the first 1GB of that file will be read soon.
.TP
-.B $ lfs ladvise -a dontneed -s 0 -e 1048576000 /mnt/lustre/file1
+.B $ lfs ladvise -a dontneed -s 0 -e 1G /mnt/lustre/file1
This gives the OST(s) holding the first 1GB of \fB/mnt/lustre/file1\fR a hint
that the first 1GB of file will not be read in the near future, thus the OST(s)
-could clear the cache of the file in the memory.
+could clear the cache of that file in the memory.
.SH AVAILABILITY
The lfs ladvise command is part of the Lustre filesystem.
.SH SEE ALSO
.BR lfs (1),
-.BR fadvise (2),
+.BR fadvise64 (2),
+.BR posix_fadvise (2),
.BR llapi_ladvise (3),
.BR lustre (7)
return 1
}
+percent() {
+ bc <<<"scale=2; ($1 - $2) * 100 / $2"
+}
+
+# run a random read IO workload
+# usage: random_read_iops <filename> <filesize> <iosize>
+random_read_iops() {
+ local file=$1
+ local fsize=$2
+ local iosize=${3:-4096}
+
+ $READS -f $file -s $fsize -b $iosize -n $((fsize / iosize)) -t 60 |
+ sed -e '/^$/d' -e 's#.*s, ##' -e 's#MB/s##'
+}
+
+drop_file_oss_cache() {
+ local file="$1"
+ local nodes="$2"
+
+ $LFS ladvise -a dontneed $file 2>/dev/null ||
+ do_nodes $nodes "echo 3 > /proc/sys/vm/drop_caches"
+}
+
ladvise_willread_performance()
{
local repeat=10
+ local average_origin=0
local average_cache=0
local average_ladvise=0
for ((i = 1; i <= $repeat; i++)); do
echo "Iter $i/$repeat: reading without willread hint"
cancel_lru_locks osc
- do_nodes $(comma_list $(osts_nodes)) \
- "echo 3 > /proc/sys/vm/drop_caches"
- local speed_origin=$($READS -f $DIR/$tfile -s $size \
- -b 4096 -n $((size / 4096)) -t 60 |
- sed -e '/^$/d' -e 's#.*s, ##' -e 's#MB/s##')
+ drop_file_oss_cache $DIR/$tfile $(comma_list $(osts_nodes))
+ local speed_origin=$(random_read_iops $DIR/$tfile $size)
+ echo "Iter $i/$repeat: uncached speed: $speed_origin"
+ average_origin=$(bc <<<"$average_origin + $speed_origin")
- echo "Iter $i/$repeat: Reading again without willread hint"
cancel_lru_locks osc
- local speed_cache=$($READS -f $DIR/$tfile -s $size \
- -b 4096 -n $((size / 4096)) -t 60 |
- sed -e '/^$/d' -e 's#.*s, ##' -e 's#MB/s##')
+ local speed_cache=$(random_read_iops $DIR/$tfile $size)
+ echo "Iter $i/$repeat: OSS cache speed: $speed_cache"
+ average_cache=$(bc <<<"$average_cache + $speed_cache")
- echo "Iter $i/$repeat: reading with willread hint"
cancel_lru_locks osc
- do_nodes $(comma_list $(osts_nodes)) \
- "echo 3 > /proc/sys/vm/drop_caches"
- lfs ladvise -a willread $DIR/$tfile ||
- error "Ladvise failed"
- local speed_ladvise=$($READS -f $DIR/$tfile -s $size \
- -b 4096 -n $((size / 4096)) -t 60 |
- sed -e '/^$/d' -e 's#.*s, ##' -e 's#MB/s##')
-
- local cache_speedup=$(echo "scale=2; \
- ($speed_cache-$speed_origin)/$speed_origin*100" | bc)
- cache_speedup=$(echo ${cache_speedup%.*})
- echo "Iter $i/$repeat: cache speedup: $cache_speedup%"
- average_cache=$((average_cache + cache_speedup))
-
- local ladvise_speedup=$(echo "scale=2; \
- ($speed_ladvise-$speed_origin)/$speed_origin*100" | bc)
- ladvise_speedup=$(echo ${ladvise_speedup%.*})
- echo "Iter $i/$repeat: ladvise speedup: $ladvise_speedup%"
- average_ladvise=$((average_ladvise + ladvise_speedup))
+ drop_file_oss_cache $DIR/$tfile $(comma_list $(osts_nodes))
+ $LFS ladvise -a willread $DIR/$tfile || error "ladvise failed"
+ local speed_ladvise=$(random_read_iops $DIR/$tfile $size)
+ echo "Iter $i/$repeat: ladvise speed: $speed_ladvise"
+ average_ladvise=$(bc <<<"$average_ladvise + $speed_ladvise")
done
- average_cache=$((average_cache / repeat))
- average_ladvise=$((average_ladvise / repeat))
-
- if [ $average_cache -lt 20 ]; then
- echo "Speedup with cache is less than 20% ($average_cache%),"\
- "skipping check of speedup with willread:"\
- "$average_ladvise%"
+ average_origin=$(bc <<<"scale=2; $average_origin / $repeat")
+ average_cache=$(bc <<<"scale=2; $average_cache / $repeat")
+ average_ladvise=$(bc <<<"scale=2; $average_ladvise / $repeat")
+
+ speedup_cache=$(percent $average_cache $average_origin)
+ speedup_ladvise=$(percent $average_ladvise $average_origin)
+
+ echo "Average uncached read: $average_origin"
+ echo "Average speedup with OSS cached read: " \
+ "$average_cache = +$speedup_cache%"
+ echo "Average speedup with ladvise willread: " \
+ "$average_ladvise = +$speedup_ladvise%"
+
+ local lowest_speedup=20
+ if [ ${average_cache%.*} -lt $lowest_speedup ]; then
+ echo "Speedup with OSS cached read less than $lowest_speedup%, "
+ "got $average_cache%. Skipping ladvise willread check."
return 0
fi
- local lowest_speedup=$((average_cache / 2))
- [ $average_ladvise -gt $lowest_speedup ] ||
+ # the test won't work on ZFS until it supports 'ladvise dontneed', but
+ # it is still good to run until then to exercise 'ladvise willread'
+ ! $LFS ladvise -a dontneed $DIR/$tfile &&
+ [ "$(facet_fstype ost1)" = "zfs" ] &&
+ echo "osd-zfs does not support dontneed or drop_caches" &&
+ return 0
+
+ lowest_speedup=$(bc <<<"scale=2; $average_cache / 2")
+ [ ${average_ladvise%.*} -gt $lowest_speedup ] ||
error_not_in_vm "Speedup with willread is less than " \
- "$lowest_speedup%, got $average_ladvise%"
- echo "Speedup with willread ladvise: $average_ladvise%"
- echo "Speedup with cache: $average_cache%"
+ "$lowest_speedup%, got $average_ladvise%"
}
test_255a() {
}
test_255b() {
+ lfs setstripe -c 1 -i 0 $DIR/$tfile
+
ladvise_no_type dontneed $DIR/$tfile &&
skip "dontneed ladvise is not supported" && return
[ $(lustre_version_code ost1) -lt $(version_code 2.8.54) ] &&
skip "lustre < 2.8.54 does not support ladvise" && return
- [ "$(facet_fstype ost1)" = "zfs" ] &&
- skip "zfs-osd does not support dontneed advice" && return
-
- lfs setstripe -c 1 -i 0 $DIR/$tfile
+ ! $LFS ladvise -a dontneed $DIR/$tfile &&
+ [ "$(facet_fstype ost1)" = "zfs" ] &&
+ skip "zfs-osd does not support 'ladvise dontneed'" && return
local size_mb=100
local size=$((size_mb * 1048576))
git://git.whamcloud.com / fs / lustre-release.git / commitdiff