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

[MaoXiaoyun <tinnycloud@xxxxxxxxxxx>]

Send the RHEL source code for convience.
I will have some performance test later.
 
In my understanding, KeSetTargetProcessorDpc(&xi->rx_dpc, num)
means put this Dpc into numth CPU dpc queue, right ?
 
What is the difference between this line of code is commentted
and  the num is set to 0? I assume they have the same mean, right?
 
Thanks.
 
> Subject: RE: Rather slow time of Pin in Windows with GPL PV driver
> Date: Wed, 9 Mar 2011 22:28:48 +1100
> From: james.harper@xxxxxxxxxxxxxxxx
> To: tinnycloud@xxxxxxxxxxx
> CC: xen-devel@xxxxxxxxxxxxxxxxxxx
>
> > 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?
>
> James

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