Re: [Xen-devel] cpuidle causing Dom0 soft lockups

To:	Jan Beulich <JBeulich@xxxxxxxxxx>
Subject:	Re: [Xen-devel] cpuidle causing Dom0 soft lockups
From:	Juergen Gross <juergen.gross@xxxxxxxxxxxxxx>
Date:	Tue, 02 Feb 2010 09:13:30 +0100
Cc:	"xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>, ke.yu@xxxxxxxxx
Delivery-date:	Tue, 02 Feb 2010 00:13:49 -0800
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Jan Beulich wrote:
>>>> Keir Fraser <keir.fraser@xxxxxxxxxxxxx> 21.01.10 12:03 >>>
>> On 21/01/2010 10:53, "Jan Beulich" <JBeulich@xxxxxxxxxx> wrote:
>>> I can see your point. But how can you consider shipping with something
>>> apparently severely broken. As said before - the fact that this manifests
>>> itself by hanging many-vCPU Dom0 has the very likely implication that
>>> there are (so far unnoticed) problems with smaller Dom0-s. If I had a
>>> machine at hand that supports C3, I'd try to do some measurements
>>> with smaller domains...
>> Well it's a fallback I guess. If we can't make progress on solving it then I
>> suppose I agree.
> 
> Just fyi, we now also have seen an issue on a 24-CPU system that went
> away with cpuidle=0 (and static analysis of the hang hinted in that
> direction). All I can judge so far is that this likely has something to do
> with our kernel's intensive use of the poll hypercall (i.e. we see vCPU-s
> not waking up from the call despite there being pending unmasked or
> polled for events).

Interesting. I see this problem on a 4-core system.
Can I help investigating?

Data of my machine (Fujitsu TX300-S5):

# cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 6
model           : 26
model name      : Intel(R) Xeon(R) CPU           E5520  @ 2.27GHz
stepping        : 5
...


Juergen

-- 
Juergen Gross                 Principal Developer Operating Systems
TSP ES&S SWE OS6                       Telephone: +49 (0) 89 3222 2967
Fujitsu Technolgy Solutions               e-mail: juergen.gross@xxxxxxxxxxxxxx
Domagkstr. 28                           Internet: ts.fujitsu.com
D-80807 Muenchen                 Company details: ts.fujitsu.com/imprint.html

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Re: [Xen-devel] cpuidle causing Dom0 soft lockups