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Re: [PATCH] Remove l_flushsema

To: David Chinner <dgc@xxxxxxx>
Subject: Re: [PATCH] Remove l_flushsema
From: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Date: Wed, 30 Apr 2008 06:58:32 -0400
Cc: Matthew Wilcox <matthew@xxxxxx>, xfs@xxxxxxxxxxx, linux-fsdevel@xxxxxxxxxxxxxxx
In-reply-to: <20080430104125.GM108924158@sgi.com>
References: <20080430090502.GH14976@parisc-linux.org> <20080430104125.GM108924158@sgi.com>
Sender: xfs-bounce@xxxxxxxxxxx
User-agent: Mutt/1.5.17 (2007-11-01)
On Wed, Apr 30, 2008 at 08:41:25PM +1000, David Chinner wrote:
> The only thing that I'm concerned about here is that this will
> substantially increase the time the l_icloglock is held. This is
> a severely contended lock on large cpu count machines and putting
> the wakeup inside this lock will increase the hold time.
> 
> I guess I can address this by adding a new lock for the waitqueue
> in a separate patch set.

waitqueues are loked internally and don't need synchronization.  With
a little bit of re-arranging the code the wake_up could probably be
moved out of the critical section.


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