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Re: [Xen-users] i/o scheduler deadlocks with loopback devices

To: Nathan Gamber <ngamber@xxxxxxxxxxxxx>
Subject: Re: [Xen-users] i/o scheduler deadlocks with loopback devices
From: Thomas Halinka <lists@xxxxxxxxx>
Date: Fri, 05 Nov 2010 18:48:10 +0100
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Hi Natham,

which kernel is ur dom0 running?



Am Freitag, den 05.11.2010, 13:30 -0400 schrieb Nathan Gamber:
> This was an email I sent to xen-devel a while ago without getting a 
> response. I'm reposting it here in case someone knows more.
>   Hello all,
> I'm able to consistently reproduce lockups in my domU with heavy I/O
> with the following error:
> 36841.420662] INFO: task rsyslogd:15014
> blocked for more than 120 seconds. [36841.420843] "echo 0>
> /proc/sys/kernel/hung_task_timeout_secs" disables this message.
> The task varies between any of the tasks that might be active
> (kjournald, loop0, etc.)
> My setup is:
> Xen dom0  version 3.4.2.
> domU: Ubuntu 10.04, 2.6.36-rc6 based on Stefano Stabellini's
> v2.6.36-rc6-urgent-fixes tree.
> Paravirtual disks and network interfaces.
> Root filesystem on /dev/xvda3, formatted ext3, mounted with default options.
> Both dom0 and domU are using the CFQ i/o scheduler.
> The xvbd is based on LVM, on top of a local SATA RAID array.
> To produce this, I can do one of the following:
> Set up domU as a primary drbd node, with my drbd volume on top of a
> local loopback device, and then rsync many files to the volume, delete
> them, and repeat until the crash.
> Mount a linux iso via loopback on a /mnt/test, rsync /mnt/test/ to
> another directory on xvda3, delete the files, and then repeat until the
> crash.
> This is very similar to the following situation:
> http://www.amailbox.org/mailarchive/linux-kernel/2010/9/1/4614107
> Jeremy Fitzhardinge replied to that thread, indicating that his "xen:
> use percpu interrupts for IPIs and VIRQs" and "xen: handle events as
> edge-triggered" patches should fix the issue. These were introduced into
> 2.6.36-rc3, I believe, and the issue persists. Disabling irqbalanced in
> dom0, as he suggested as a workaround, has no effect. I've also tried
> changing the scheduler, and reducing the number of vcpus from 4 to 1,
> which also had no effect.
> Regards,
> Nathan Gamber
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