Re: [Xen-devel] [PATCH, RFC] x86/HVM: batch vCPU wakeups

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 09.09.14 at 11:33, <pasik@xxxxxx> wrote:
> On Tue, Sep 09, 2014 at 09:33:37AM +0100, Jan Beulich wrote:
>> Mass wakeups (via vlapic_ipi()) can take enormous amounts of time,
>> especially when many of the remote pCPU-s are in deep C-states. For
>> 64-vCPU Windows Server 2012 R2 guests on Ivybridge hardware,
>> accumulated times of over 2ms were observed. Considering that Windows
>> broadcasts IPIs from its timer interrupt, which at least at certain
>> times can run at 1kHz, it is clear that this can result in good
>> guest behavior.
> 
> I guess that should say "it is clear that this *can't* result in good guest 
> behaviour" .. 

Of course - thanks for spotting.

Jan


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