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Re: [Xen-devel] Xen spinlock questions
| To: | Jan Beulich <jbeulich@xxxxxxxxxx>, Jeremy Fitzhardinge <jeremy@xxxxxxxx> |
|---|---|
| Subject: | Re: [Xen-devel] Xen spinlock questions |
| From: | Keir Fraser <keir.fraser@xxxxxxxxxxxxx> |
| Date: | Mon, 04 Aug 2008 11:24:19 +0100 |
| Cc: | xen-devel@xxxxxxxxxxxxxxxxxxx |
| Delivery-date: | Mon, 04 Aug 2008 03:24:45 -0700 |
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| Thread-topic: | [Xen-devel] Xen spinlock questions |
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On 4/8/08 11:18, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote: > 1) While the goal of the per-CPU kicker irq appears to be to avoid all CPUs > waiting for a particular lock to get kicked simultaneously, I think this > doesn't have the desired effect. This is because Xen doesn't track what > event channel you poll for (through SCHEDOP_poll), and rather kicks all CPUs > polling for any event channel. 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. -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel |
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