Re: [Xen-devel] pvops domu soft lockup under load (more logs)

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

On 04/15/2010 03:56 AM, Pim van Riezen wrote:
> On Apr 14, 2010, at 19:48 , Jeremy Fitzhardinge wrote:
>
>   
>> Does it appear on the Xen console (visible with "xm dmesg")?  You may
>> need to do a sysrq '9' first to get it to output all messages.
>>     
> Does that sysrq have to go to dom0 or to the domU?
>   

To the locked-up domU.

> I also got the tip from someone on xen-users to take a look at the clock 
> source, and setting 
> /sys/devices/system/clocksource/clocksource0/current_clocksource to 'jiffies' 
> does seem to stop the lockups from happening. The fact that I've witnessed 
> other kernel timekeeping going wonky on these guests, the fact that this 
> helps does seem intuitively right, but I don't know if it gives you enough to 
> work with.
>   

I've seen similar lockups at a very low rate.  The clocksource
workaround just confuses me; the whole thing stumps me.  The main piece
of evidence I haven't managed to get yet is a complete process dump
(sysrq-t) to see who's waiting on what.

Also, could you try 2.6.32.11, which has some timer-related fixes in it,
that may or may not help.

    J


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