diff options
author | Zhang, Yanmin <yanmin_zhang@linux.intel.com> | 2009-07-05 15:08:08 -0400 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-07-06 16:57:03 -0400 |
commit | 3beab0b42413e83a7907db7176b54c840fc75a81 (patch) | |
tree | 385c4e725fb56c0416be1512b50c357e9bc50b6b | |
parent | f386c61fe1a1f36f0e434f1b577e6b112698caf7 (diff) |
sys_sync(): fix 16% performance regression in ffsb create_4k test
I run many ffsb test cases on JBODs (typically 13/12 disks). Comparing
with kernel 2.6.30, 2.6.31-rc1 has about 16% regression with
ffsb_create_4k. The sub test case creates files continuously for 10
minitues and every file is 1MB.
Bisect located below patch.
5cee5815d1564bbbd505fea86f4550f1efdb5cd0 is first bad commit
commit 5cee5815d1564bbbd505fea86f4550f1efdb5cd0
Author: Jan Kara <jack@suse.cz>
Date: Mon Apr 27 16:43:51 2009 +0200
vfs: Make sys_sync() use fsync_super() (version 4)
It is unnecessarily fragile to have two places (fsync_super() and do_sync())
doing data integrity sync of the filesystem. Alter __fsync_super() to
accommodate needs of both callers and use it. So after this patch
__fsync_super() is the only place where we gather all the calls needed to
properly send all data on a filesystem to disk.
As a matter of fact, ffsb calls sys_sync in the end to make sure all data
is flushed to disks and the flushing is counted into the result. vmstat
shows ffsb is blocked when syncing for a long time. With 2.6.30, ffsb is
blocked for a short time.
I checked the patch and did experiments to recover the original methods.
Eventually, the root cause is the patch deletes the calling to
wakeup_pdflush when syncing, so only ffsb is blocked on disk I/O.
wakeup_pdflush could ask pdflush to write back pages with ffsb at the
same time.
[akpm@linux-foundation.org: restore comment too]
Signed-off-by: Zhang Yanmin <yanmin_zhang@linux.intel.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r-- | fs/sync.c | 5 |
1 files changed, 5 insertions, 0 deletions
@@ -112,8 +112,13 @@ restart: | |||
112 | mutex_unlock(&mutex); | 112 | mutex_unlock(&mutex); |
113 | } | 113 | } |
114 | 114 | ||
115 | /* | ||
116 | * sync everything. Start out by waking pdflush, because that writes back | ||
117 | * all queues in parallel. | ||
118 | */ | ||
115 | SYSCALL_DEFINE0(sync) | 119 | SYSCALL_DEFINE0(sync) |
116 | { | 120 | { |
121 | wakeup_pdflush(0); | ||
117 | sync_filesystems(0); | 122 | sync_filesystems(0); |
118 | sync_filesystems(1); | 123 | sync_filesystems(1); |
119 | if (unlikely(laptop_mode)) | 124 | if (unlikely(laptop_mode)) |