linux-kernel - Re: [PATCH 1/5] Add a global synchronization point for pvclock

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Message-ID: <4BCC3520.6090305@redhat.com>
Date:	Mon, 19 Apr 2010 13:49:04 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Glauber Costa <glommer@...hat.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Marcelo Tosatti <mtosatti@...hat.com>,
	Zachary Amsden <zamsden@...hat.com>
Subject: Re: [PATCH 1/5] Add a global synchronization point for pvclock

On 04/19/2010 01:46 PM, Peter Zijlstra wrote:
> On Sat, 2010-04-17 at 21:48 +0300, Avi Kivity wrote:
>    
>>> After this patch is applied, I don't see a single warp in time during 5 days
>>> of execution, in any of the machines I saw them before.
>>>
>>>
>>>        
>> Please define a cpuid bit that makes this optional.  When we eventually
>> enable it in the future, it will allow a wider range of guests to enjoy it.
>>      
> Right, so on x86 we have:
>
> X86_FEATURE_CONSTANT_TSC, which only states that TSC is frequency
> independent, not that it doesn't stop in C states and similar fun stuff.
>
> X86_FEATURE_TSC_RELIABLE, which IIRC should indicate the TSC is constant
> and synced between cores.
>
>    

Sockets and boards too?  (IOW, how reliable is TSC_RELIABLE)?

-- 
error compiling committee.c: too many arguments to function

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