The patch titled
sys_sync(): fix 16% performance regression in ffsb create_4k test
has been removed from the -mm tree. Its filename was
sys_sync-fix-16%-performance-regression-in-ffsb-create_4k-test.patch
This patch was dropped because it was merged into mainline or a subsystem tree
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: sys_sync(): fix 16% performance regression in ffsb create_4k test
From: "Zhang, Yanmin" <yanmin_zhang@xxxxxxxxxxxxxxx>
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@xxxxxxx>
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@xxxxxxxxxxxxxxxxxxxx: restore comment too]
Signed-off-by: Zhang Yanmin <yanmin_zhang@xxxxxxxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Acked-by: Jens Axboe <jens.axboe@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/sync.c | 5 +++++
1 file changed, 5 insertions(+)
diff -puN fs/sync.c~sys_sync-fix-16%-performance-regression-in-ffsb-create_4k-test fs/sync.c
--- a/fs/sync.c~sys_sync-fix-16%-performance-regression-in-ffsb-create_4k-test
+++ a/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))
_
Patches currently in -mm which might be from yanmin_zhang@xxxxxxxxxxxxxxx are
kernel-core-add-smp_call_function_any.patch
kernel-core-add-smp_call_function_any-update.patch
arch-x86-kernel-cpu-cpufreq-acpi-cpufreqc-avoid-cross-cpu-interrupts-by-using-smp_call_function_any.patch
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