linux-kernel - Re: rename() contention (BUG?)

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Date:	Thu, 26 Oct 2006 20:43:34 +0200
From:	Avi Kivity <avi@...o.co.il>
To:	Josef Sipek <jsipek@....cs.sunysb.edu>
CC:	lkml@...garu.com, linux-kernel@...r.kernel.org
Subject: Re: rename() contention (BUG?)

Josef Sipek wrote:
> On Wed, Oct 25, 2006 at 03:56:34PM -0500, lkml@...garu.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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