linux-kernel - Re: XFS vs Elevators (was Re: [PATCH RFC] nilfs2: continuous snapshotting file system)

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Message-ID: <48AD224A.7080107@gelato.unsw.edu.au>
Date:	Thu, 21 Aug 2008 18:07:38 +1000
From:	Aaron Carroll <aaronc@...ato.unsw.edu.au>
To:	david@...morbit.com
CC:	Szabolcs Szakacsits <szaka@...s-3g.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	xfs@....sgi.com
Subject: Re: XFS vs Elevators (was Re: [PATCH RFC] nilfs2: continuous	snapshotting
 file system)

Dave Chinner wrote:
> One thing I just found out - my old *laptop* is 4-5x faster than the
> 10krpm scsi disk behind an old cciss raid controller.  I'm wondering
> if the long delays in dispatch is caused by an interaction with CTQ
> but I can't change it on the cciss raid controllers. Are you using
> ctq/ncq on your machine?  If so, can you reduce the depth to
> something less than 4 and see what difference that makes?

I've been benchmarking on a cciss card, and patched the driver to
control the queue depth via sysfs.  Maybe you'll find it useful...

The original patch was for 2.6.24, but that won't apply on git head.
I fixed it for 2.6.27, and it seems to work fine.  Both are attached.


   -- Aaron


View attachment "cciss_qdepth-2.6.24.patch" of type "text/plain" (4025 bytes)

View attachment "cciss_qdepth-2.6.27.patch" of type "text/plain" (3974 bytes)