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Re: [Xen-devel] Re: VM hung after running sometime

To: MaoXiaoyun <tinnycloud@xxxxxxxxxxx>
Subject: Re: [Xen-devel] Re: VM hung after running sometime
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Wed, 29 Sep 2010 09:12:07 -0700
Cc: xen devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, keir.fraser@xxxxxxxxxxxxx
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User-agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.9) Gecko/20100921 Fedora/3.1.4-1.fc13 Lightning/1.0b3pre Thunderbird/3.1.4
 On 09/28/2010 11:01 PM, MaoXiaoyun wrote:
> Well, I just go throught the source of irqbalance, it shows that it
> balances the irq through
> updating /proc/irq/$irq/smp_affinity. That, in my understanding, set
> irq affinity is almost
> equal to irq migration.

Correct.

>
> I later find the NIC interrupt is not modified in dom0, so it is safe
> to set its affinity,
> but interrupt of xen event use handle_level_irq, set its affinity will
> subject to irq
> lost.
>
> Am I right?

I can't parse that sentence so I'm not sure. But if you have
successfully migrated the interrupt/evtchn to a different vcpu, then
there's no subsequent risk of lost events. The event loss can only
happen in the circumstance I mentioned earlier: when you migrate while
an event is being handled, and a second event occurs on the new cpu
before the first one has finished. So you need both bad timing and a
fairly high event delivery rate to trigger the problem.

J


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