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Re: [Xen-devel] Xen spinlock questions

To: Jan Beulich <jbeulich@xxxxxxxxxx>
Subject: Re: [Xen-devel] Xen spinlock questions
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Mon, 11 Aug 2008 11:10:06 -0700
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
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Jan Beulich wrote:
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.

What exactly are you measuring here? Are you testing your 2.6.2x forward-port with an adaptation of pv spinlocks using ticket locks as the underlying locking mechanism? Does the 10% improvement come compared to straightforward use of sched_poll, or compared to doing spurious wakeup detection?

   J

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