linux-kernel - Re: Postal 56% waits for flock_lock_file

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Date:	Mon, 02 Oct 2006 13:11:21 -0400
From:	Trond Myklebust <trond.myklebust@....uio.no>
To:	Tim Chen <tim.c.chen@...el.com>
Cc:	"Ananiev, Leonid I" <leonid.i.ananiev@...el.com>,
	Linux Kernel Mailing List <Linux-Kernel@...r.kernel.org>
Subject: Re: Postal 56% waits for flock_lock_file_wait

On Mon, 2006-10-02 at 09:57 -0700, Tim Chen wrote:
> On 10/1/06, Trond Myklebust <trond.myklebust@....uio.no> wrote:
> 
> >
> > I still don't get it. The job of the flock() system call is to sleep if
> > someone already holds the lock, and then grab the lock when it is
> > released. If that is not what the user expects, then the user has the
> > option of not calling flock(). This has nothing to do with open().
> >
> > Trond
> >
> 
> If I understand Leonid correctly, I think what he is saying is ext3
> does not scale very well when you have a large number of processes
> acessing file system because of locks in journal.    This is seen in
> the excessive idle time.  By comparison, ext2 does not have this
> issue.

Ext3 does not use flock() in order to lock its journal. The performance
issues that he is seeing may well be due to the journalling, but that
has nothing to do with flock_lock_file_wait.

Cheers,
  Trond

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