From: Zachary Amsden <zamsden@redhat.com>
To: Bernhard Schmidt <berni@birkenwald.de>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: Clock jumps
Date: Thu, 27 May 2010 12:22:29 -1000 [thread overview]
Message-ID: <4BFEF0A5.8040301@redhat.com> (raw)
In-Reply-To: <4BFEEE3A.1010403@birkenwald.de>
On 05/27/2010 12:12 PM, Bernhard Schmidt wrote:
> On 27.05.2010 23:53, Zachary Amsden wrote:
>
> Hello Zachary,
>
>> I have server side fixes for this kvm-clock which seem to give me a
>> stable clock on this machine, but for true SMP stability, you will need
>> Glauber's guest side changes to kvmclock as well. It is impossible to
>> guarantee strictly monotonic clocksource across multiple CPUs when
>> frequency is dynamically changing (and also because of the C1E idle
>> problems).
>
> Is all this relevant only when the host is on TSC? Because I have seen
> these jumps when the host was on HPET and the guests were using
> kvm-clock.
It doesn't matter what the host uses (although the host on TSC with
unstable TSC can make things worse), tsc and kvmclock sources in the
guest will be unstable regardless.
next prev parent reply other threads:[~2010-05-27 22:22 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <loom.20100524T171038-56@post.gmane.org>
2010-05-25 6:21 ` Clock jumps Gleb Natapov
2010-05-26 17:10 ` Orion Poplawski
2010-05-26 17:31 ` Alexander Graf
2010-05-26 17:50 ` Orion Poplawski
2010-05-26 22:55 ` Orion Poplawski
2010-05-27 18:32 ` Bernhard Schmidt
2010-05-27 19:08 ` john stultz
2010-05-27 21:48 ` Bernhard Schmidt
2010-05-28 0:00 ` john stultz
2010-05-28 0:33 ` Bernhard Schmidt
2010-05-28 0:46 ` john stultz
2010-05-27 21:53 ` Zachary Amsden
2010-05-27 22:12 ` Bernhard Schmidt
2010-05-27 22:20 ` Zachary Amsden
2010-05-27 22:22 ` Zachary Amsden [this message]
2010-06-02 22:54 ` Orion Poplawski
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