diff options
| author | Zhang, Yanmin <yanmin_zhang@linux.intel.com> | 2009-07-05 12:08:08 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-07-06 13:57:03 -0700 |
| 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
diff --git a/fs/sync.c b/fs/sync.c index dd200025af8..3422ba61d86 100644 --- a/fs/sync.c +++ b/fs/sync.c @@ -112,8 +112,13 @@ restart: mutex_unlock(&mutex); } +/* + * sync everything. Start out by waking pdflush, because that writes back + * all queues in parallel. + */ SYSCALL_DEFINE0(sync) { + wakeup_pdflush(0); sync_filesystems(0); sync_filesystems(1); if (unlikely(laptop_mode)) |