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From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: bugzilla-daemon@bugzilla.kernel.org
Cc: linux-scsi@vger.kernel.org
Subject: Re: [Bug 41552] Performance of writing and reading from multiple drives decreases by 40% when going from Linux Kernel 2.6.36.4 to 2.6.37 (and beyond)
Date: Tue, 23 Aug 2011 09:00:57 -0500	[thread overview]
Message-ID: <1314108057.13645.8.camel@mulgrave> (raw)
In-Reply-To: <201108222107.p7ML767K019660@demeter2.kernel.org>

On Mon, 2011-08-22 at 21:07 +0000, bugzilla-daemon@bugzilla.kernel.org
wrote:
> We were using the default CFQ scheduler.  I will change it to deadline and see
> what happens.  Also, we are not using a file system to perform the writes,
> rather we are sending SCSI commands directly to the devices, nor are we doing
> anything special to the disks with a device mapper.  We simply write to each
> one on a different thread one sector at a time.
> 
> I will attempt to get the trace and will add it if I can.

If you're just using a SG_IO type scsi command, then virtually nothing
we've done in block/scsi should affect this; certainly not the elevators
since we don't do merging on SG_IO, we just use them for queueing.
Since you say "write to each one on a different thread", it's possible
that some scheduler change may have impacted this.

James



  reply	other threads:[~2011-08-23 14:01 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-08-22 15:20 [Bug 41552] New: Performance of writing and reading from multiple drives decreases by 40% when going from Linux Kernel 2.6.36.4 to 2.6.37 (and beyond) bugzilla-daemon
2011-08-22 15:21 ` [Bug 41552] " bugzilla-daemon
2011-08-22 15:22 ` bugzilla-daemon
2011-08-22 15:22 ` bugzilla-daemon
2011-08-22 19:25 ` bugzilla-daemon
2011-08-22 19:25 ` bugzilla-daemon
2011-08-22 20:21 ` bugzilla-daemon
2011-08-22 20:21 ` bugzilla-daemon
2011-08-22 20:24 ` bugzilla-daemon
2011-08-22 21:02 ` bugzilla-daemon
2011-08-22 21:07 ` bugzilla-daemon
2011-08-23 14:00   ` James Bottomley [this message]
2011-08-23 14:38 ` bugzilla-daemon
2011-08-24 20:46 ` bugzilla-daemon
2011-08-25 21:02 ` bugzilla-daemon
2012-08-30 10:41 ` bugzilla-daemon

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