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[Xen-devel] RE: TSC virtualization across different host frequency platf

To: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] RE: TSC virtualization across different host frequency platform migration
From: "Dong, Eddie" <eddie.dong@xxxxxxxxx>
Date: Wed, 22 Apr 2009 16:49:43 +0800
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Cc: "Tian, Kevin" <kevin.tian@xxxxxxxxx>, "Dong, Eddie" <eddie.dong@xxxxxxxxx>, "Zhang, Xiantao" <xiantao.zhang@xxxxxxxxx>
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Thread-topic: TSC virtualization across different host frequency platform migration
Keir Fraser wrote:
> On 22/04/2009 02:32, "Dong, Eddie" <eddie.dong@xxxxxxxxx> wrote:
>> Keir and all:
>> Recently we are considering the potential issue of TSC
>> virtualization across different frequency platform migration.
>> Current approach will lead to synchronization issue between guest
>> TSC and wall clock. Software trap and emulate can solve the problem
>> with the payment of performance overhead which is not optimal. We
>> want to propose smart scaling algorithm which can continuously use
>> HW TSC_OFFSET and maintain long time synchronization of guest TSC. 
>> The details are in attached document. Can you have a look and
>> provide comments? 
> The important questions are: What guests get confused by an
> out-of-sync TSC? And is coarse-grained re-sync (multi-second

That is what I am interested too. Is there any report from real deployment
which utilize migration frequently? 

thx, eddie

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