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Date:      Sat, 25 Sep 2010 11:40:39 +0200
From:      Marius Strobl <marius@alchemy.franken.de>
To:        Lawrence Stewart <lstewart@freebsd.org>
Cc:        svn-src-head@freebsd.org, svn-src-all@freebsd.org, src-committers@freebsd.org
Subject:   Re: svn commit: r213105 - head/sys/dev/mpt
Message-ID:  <20100925094039.GS46946@alchemy.franken.de>
In-Reply-To: <4C9D7068.2010100@freebsd.org>
References:  <201009241640.o8OGelKS031911@svn.freebsd.org> <4C9D7068.2010100@freebsd.org>

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On Sat, Sep 25, 2010 at 01:45:44PM +1000, Lawrence Stewart wrote:
> Hi Marius,
> 
> On 09/25/10 02:40, Marius Strobl wrote:
> > Author: marius
> > Date: Fri Sep 24 16:40:46 2010
> > New Revision: 213105
> > URL: http://svn.freebsd.org/changeset/base/213105
> > 
> > Log:
> >   Improve r56796; the reply handler actually may remove the request from
> >   the chain in which case it shouldn't be removed twice.
> >   Reported by:	Staale Kristoffersen
> 
> Can you please provide a bit of extra commentary about the symptoms of
> the issue this patch addresses? Like Staale, I'm running a FreeBSD
> server which uses mpt for its disk subsystem (SunFire X4100 with 2 x
> SATA 2.5" disks in RAID-1) and I've had a series of long running
> problems with the performance of the controller. I'm keeping a close eye
> on all mpt related commits and hope to find the cause sometime.
> 

In case the reply handler also removed the request this triggered
a sanity check in TAILQ_REMOVE with INVARIANTS compiled in, causing
a panic. I don't think it had a negative impact with INVARIANTS
disabled. Also, in order to hit the problem you first had to run
into a timeout leading to an IOC rest like here:
http://folk.uio.no/stalk/mpt/timeout.txt
i.e. I don't think this is related to your performance issue.

Marius




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