linux-kernel - Re: kvm: odd time values since "kvmclock: set scheduler clock stable"

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Message-ID: <20150518223936.GA4486@amt.cnet>
Date:	Mon, 18 May 2015 19:39:36 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	KVM General <kvm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Paolo Bonzini <pbonzini@...hat.com>, lcapitulino@...hat.com
Subject: Re: kvm: odd time values since "kvmclock: set scheduler clock stable"

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?


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