RE: Postal 56% waits for flock_lock_file_wait
- From: "Ananiev, Leonid I" <leonid.i.ananiev@xxxxxxxxx>
- Date: Sat, 30 Sep 2006 21:26:40 +0400
On which filesystem were the above results obtained if it was notext2?
The default ext3 fs was used.
All the above results are telling you is that your test involvesseveral
processes contending for the same lock, and so all of them barring the
one process that actually holds the lock are idle.
Yes. It is flock_lock_file_wait.
Leonid
-----Original Message-----
From: Trond Myklebust [mailto:trond.myklebust@xxxxxxxxxx]
Sent: Saturday, September 30, 2006 7:06 PM
To: Ananiev, Leonid I
Cc: Linux Kernel Mailing List
Subject: Re: Postal 56% waits for flock_lock_file_wait
On Sat, 2006-09-30 at 09:25 +0400, Ananiev, Leonid I wrote:
A benchmark50%
'postal -p 16 localhost list_of_1000_users'
56% of run time waits for flock_lock_file_wait;
Vmstat reports that 66% cpu is idle and vmstat bi+bo=3600 (far from
max).
Postfix server with FD_SETSIZE=2048 was used.
Similar results got for sendmail.
Wchan is counted by
while :; do
ps -o user,wchan=WIDE-WCHAN-COLUMN,comm;
sleep 1;
done | awk '/ postfix /{a[$2]++}END{for (i in a) print
a[i]"\t"i}'
If ext2 fs is used the Postal throughput is twice more and bi+bo by
less while flock_lock_file_wait 60% still.
On which filesystem were the above results obtained if it was not ext2?
Is flock_lock_file_wait considered as a performance limiting waitingfor
similar applications in smp?
All the above results are telling you is that your test involves several
processes contending for the same lock, and so all of them barring the
one process that actually holds the lock are idle.
As for the throughput issue, that really depends on the filesystem you
are measuring. For remote filesystems like NFS, locks can _really_ slow
down performance because they are often required to flush all dirty data
to disk prior to releasing the lock (so that it becomes visible to
processes on other clients that might subsequently obtain the lock).
Cheers,
Trond
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