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[Xen-devel] RE: Rather slow time of Pin in Windows with GPL PV driver

To: "MaoXiaoyun" <tinnycloud@xxxxxxxxxxx>
Subject: [Xen-devel] RE: Rather slow time of Pin in Windows with GPL PV driver
From: "James Harper" <james.harper@xxxxxxxxxxxxxxxx>
Date: Thu, 10 Mar 2011 17:27:06 +1100
Cc: xen devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
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Thread-topic: Rather slow time of Pin in Windows with GPL PV driver
> It looks like KeSetTargetProcessorDpc(&xi->rx_dpc, 0) set the rx_dpc
in VCPU0
> only,
> and in fact interrput for xennet are distributed across all VCPUS.
> By using IntFiltr from http://support.microsoft.com/kb/252867
> to set interrupt affinity to VCPU0 only, without
> commentted, we get quite stable ping time too., which is less than 1ms
> So I think this is the problem.
>  KeSetTargetProcessorDpc should be discard.

Ah. So when the cpu for the irq is different to the cpu for the dpc, you
get the extra delay. That makes sense. It would also explain why XP
didn't seem to see the same problem as I think the IRQ is directed to
CPU0 there... I've been looking for the docs on what's different and
can't find anything.

If you can confirm that you have no problems with removing
KeSetTargetProcessorDpc I'll remove it, at least for >W2003 builds until
I find the docs about what NDIS expects to do on what CPU.


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