Message-ID: <454101D6.9050004@argo.co.il>
Date: Thu, 26 Oct 2006 20:43:34 +0200
From: Avi Kivity <avi@argo.co.il>
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To: Josef Sipek <jsipek@fsl.cs.sunysb.edu>
CC: lkml@pengaru.com, linux-kernel@vger.kernel.org
Subject: Re: rename() contention (BUG?)
References: <20061025205634.GB9100@shells.gnugeneration.com> <20061025211341.GB7128@filer.fsl.cs.sunysb.edu>
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Josef Sipek wrote:
> On Wed, Oct 25, 2006 at 03:56:34PM -0500, lkml@pengaru.com wrote:
>   
>> Hello,
>>
>> I have seen some scalability problems with Maildir-based mail systems running on
>> Linux (debian sarge, 2.6.8), and after much investigation I found a large part
>> of the problem was rename() contention.
>>     
>  
> Just FYI, around 2.6.15 the i_sem was replace with i_mutex which is much
> better/faster. (And I would strongly suggest you upgrade.) I would actually
> like to know how much the lock contention decresed for your case.
>   

The changes make the mutex more efficient, but won't decrease the 
contention.  It seems that all renames in one filesystem are serialized, 
and if the renames require I/O (which is certainly the case with nfs), 
rename throughput is severely limited.


-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.

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