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From: Marcelo Tosatti <mtosatti@redhat.com>
To: Sasha Levin <sasha.levin@oracle.com>
Cc: KVM General <kvm@vger.kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	lcapitulino@redhat.com
Subject: Re: kvm: odd time values since "kvmclock: set scheduler clock stable"
Date: Mon, 18 May 2015 21:13:31 -0300	[thread overview]
Message-ID: <20150519001331.GA15517@amt.cnet> (raw)
In-Reply-To: <555A79A5.608@oracle.com>

GOn Mon, May 18, 2015 at 07:45:41PM -0400, Sasha Levin wrote:
> On 05/18/2015 06:39 PM, Marcelo Tosatti wrote:
> > On Tue, May 12, 2015 at 07:17:24PM -0400, Sasha Levin wrote:
> >> Hi all,
> >>
> >> I'm seeing odd jump in time values during boot of a KVM guest:
> >>
> >> [...]
> >> [    0.000000] tsc: Detected 2260.998 MHz processor
> >> [3376355.247558] Calibrating delay loop (skipped) preset value..
> >> [...]
> >>
> >> I've bisected it to:
> > 
> > Paolo, Sasha,
> > 
> > Although this might seem undesirable, there is no requirement 
> > for sched_clock to initialize at 0:
> > 
> > "
> >  *
> >  * There is no strict promise about the base, although it tends to start
> >  * at 0 on boot (but people really shouldn't rely on that).
> >  *
> > "
> > 
> > Sasha, are you seeing any problem other than the apparent time jump?
> 
> Nope, but I've looked at it again and it seems that it jumps to the host's
> clock (that is, in the example above the 3376355 value was the host's clock
> value).
> 
> 
> Thanks,
> Sasha

Sasha, thats right. Its the host monotonic clock.



  reply	other threads:[~2015-05-19  0:13 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-05-12 23:17 kvm: odd time values since "kvmclock: set scheduler clock stable" Sasha Levin
2015-05-13 12:58 ` Luiz Capitulino
2015-05-13 15:38   ` Sasha Levin
2015-05-13 17:16   ` Paolo Bonzini
2015-05-18 22:39 ` Marcelo Tosatti
2015-05-18 23:45   ` Sasha Levin
2015-05-19  0:13     ` Marcelo Tosatti [this message]
2015-05-19  2:02       ` Sasha Levin
2015-05-19  2:13         ` Sasha Levin
2015-05-22  0:40           ` KVM: x86: zero kvmclock_offset when vcpu0 initializes kvmclock system MSR Marcelo Tosatti
2015-05-22  0:41           ` kvm: odd time values since "kvmclock: set scheduler clock stable" Marcelo Tosatti
2015-05-26 13:21             ` Luiz Capitulino
2015-05-26 13:25               ` Sasha Levin

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