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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: Wed, 9 Mar 2011 22:28:48 +1100
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Thread-topic: Rather slow time of Pin in Windows with GPL PV driver
> I may try pin later, my host has 4 * 4 core CPU.
> Well, I just compare GPL and RHEL PV driver codes, I noticed most of
the net
> driver
> initialization is the same. Only one difference, in  GPL code has the
code of
> KeSetTargetProcessorDpc(&xi->rx_dpc, 0); //in xennet_rx.c line 953
> but the RHEL doesn't
> So I simply comments the code, recompile and did the test again.
> The result shows good, all ping time less than < 1ms.
> May it be the cause? Is it harmful to comments this line?
> Many thanks.

At a guess I would say it should be harmful to performance, but all the
critical code is protected by spinlocks.

It could be a leftover from a previous version of GPLPV. In the current
version, the spinlock protected code is probably a little long winded
but is nothing compared to the passing down of packets to Windows that
is done in the DPC but outside the spinlock.

Can you do some general performance tests with this change?

Is the RHEL PV driver source publicly available?


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