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Re: [Xen-devel] Xen spinlock questions

To: Jan Beulich <jbeulich@xxxxxxxxxx>
Subject: Re: [Xen-devel] Xen spinlock questions
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Mon, 11 Aug 2008 13:25:48 +0100
Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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On 11/8/08 13:22, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:

>> Yes, this is true. We could easily do something better for VCPUs polling a
>> single event channel though, but there hasn't been a need up to now. I
>> suppose it depends how often we have multiple VCPUs stuck waiting for
>> spinlocks. I can sort out a Xen-side patch if someone wanted to measure the
>> benefits from more selective wakeup from poll.
> Running kernel builds on 8 vCPU-s competing for 4 pCPU-s shows a 10%
> improvement in performance with the individual wakeup (patch attached
> - probably sub-optimal, but I didn't seem to be able to think of a lock-less
> mechanism to achieve the desired behavior), using ticket locks in the
> kernel.

Hardly a real-world benchmark. :-)

 -- Keir

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