From mboxrd@z Thu Jan  1 00:00:00 1970
From: Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: About preemption timer
Date: Tue, 17 Dec 2013 12:22:08 +0100
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Cc: kvm <kvm@vger.kernel.org>, Jan Kiszka <jan.kiszka@web.de>
To: Arthur Chunqi Li <yzt356@gmail.com>
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Il 17/12/2013 10:32, Arthur Chunqi Li ha scritto:
> Hi Jan and Paolo,
> 
> I've tried to use preemption timer in KVM to trap vcpu regularly, but
> there's something unexpected. I run a VM with 4 vcpus and give them
> the same preemption timer value (e.g. 1000000) with all bits set
> (activate/save bits), then reset the value in preemption time-out
> handler.
> 
> Thus I expected these vcpus trap regularly in some special turns. But
> I found that when the VM is not busy, some vcpus are trapped much less
> frequently than others. In Intel SDM, I noticed that preemption timer
> is only related to TSC, and I think all the vcpus should trap in a
> similar frequency.

Does the preemption timer testcase pass on your machine?  The preemption
timer is known to have bugs.

Paolo