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Re: [Xen-devel] [PATCH] x86 hvm: freeze PIT/LAPIC timer emulation while
| To: | Kouya Shimura <kouya@xxxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx> |
|---|---|
| Subject: | Re: [Xen-devel] [PATCH] x86 hvm: freeze PIT/LAPIC timer emulation while its IRQ is masked |
| From: | Keir Fraser <keir.fraser@xxxxxxxxxxxxx> |
| Date: | Thu, 10 Sep 2009 07:49:04 +0100 |
| Cc: | |
| Delivery-date: | Wed, 09 Sep 2009 23:50:18 -0700 |
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| Thread-topic: | [Xen-devel] [PATCH] x86 hvm: freeze PIT/LAPIC timer emulation while its IRQ is masked |
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Although I can see the sense here, the patch makes me a bit uneasy. Also I think neater code would result from simply making vpt.c's handling of periodic timers less stupid. By this I mean that calling set_timer() from the timer handler is not really necessary -- you already know an interrupt is now pending and the vcpu is kicked. May as well not set_timer() until the pending interrupt(s) are delivered. That would then effectively get your optimisation "for free", wouldn't it? -- Keir On 10/09/2009 06:47, "Kouya Shimura" <kouya@xxxxxxxxxxxxxx> wrote: > Hi, > > I've found that modern windows OS never use the PIT timer, > and neither cpu#0's LAPIC timer after boot. > Despite that, xen emulates them busily. It's inefficient. > > Note: this patch ignores the IRQ mask of legacy i8259 since > rombios frequently modifies it. > > Thanks, > Kouya > > Signed-off-by: Kouya Shimura <kouya@xxxxxxxxxxxxxx> > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel |
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