From: Paolo Bonzini <pbonzini@redhat.com>
To: Jan Kiszka <jan.kiszka@web.de>
Cc: Arthur Chunqi Li <yzt356@gmail.com>,
kvm@vger.kernel.org, gleb@redhat.com, "Zhang,
Yang Z" <yang.z.zhang@intel.com>
Subject: Re: [PATCH v5] KVM: nVMX: Fully support of nested VMX preemption timer
Date: Thu, 03 Oct 2013 10:09:26 +0200 [thread overview]
Message-ID: <524D2636.8070906@redhat.com> (raw)
In-Reply-To: <52493F8C.6040009@web.de>
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Il 30/09/2013 11:08, Jan Kiszka ha scritto:
> On 2013-09-26 17:04, Paolo Bonzini wrote:
>> Hi all,
>>
>> the test fails for me if the preemption timer value is set to a
>> value that is above ~2000 (which means ~65000 TSC cycles on this
>> machine). The preemption timer seems to count faster than what
>> is expected, for example only up to 4 million cycles if you set
>> it to one million. So, I am leaving the patch out of kvm/queue
>> for now, until I can test it on more processors.
>
> I've done some measurements with the help of ftrace on the time it
> takes to let the preemption timer trigger (no adjustments via
> Arthur's patch were involved): On my Core i7-620M, the preemption
> timer seems to tick almost 10 times faster than spec and scale
> value (5) suggests. I've loaded a value of 100000, and it took
> about 130 µs until I got a vmexit with reason PREEMPTION_TIMER (no
> other exists in between).
10x is similar to what I was observing.
Paolo
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prev parent reply other threads:[~2013-10-03 8:09 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-16 8:11 [PATCH v5] KVM: nVMX: Fully support of nested VMX preemption timer Arthur Chunqi Li
2013-09-22 7:47 ` Gleb Natapov
2013-09-25 13:58 ` Paolo Bonzini
2013-09-26 15:04 ` Paolo Bonzini
2013-09-26 17:19 ` Jan Kiszka
2013-09-26 17:47 ` Paolo Bonzini
2013-09-26 20:44 ` Paolo Bonzini
2013-09-27 6:37 ` Jan Kiszka
2013-09-29 16:24 ` Jan Kiszka
2013-09-29 11:30 ` Gleb Natapov
2013-09-30 9:08 ` Jan Kiszka
2013-10-02 18:47 ` Jan Kiszka
2013-10-10 16:12 ` Jan Kiszka
2013-10-10 16:20 ` Paolo Bonzini
2013-10-25 9:56 ` Paolo Bonzini
2013-10-25 9:59 ` Jan Kiszka
2013-10-11 8:17 ` Arthur Chunqi Li
2013-10-03 8:09 ` Paolo Bonzini [this message]
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