RE: TSC virtualization across different host frequency platform migration

From: "Dong, Eddie" <eddie.dong@intel.com>
To: Keir Fraser <keir.fraser@eu.citrix.com>,
	"xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>
Cc: "Tian, Kevin" <kevin.tian@intel.com>,
	"Dong, Eddie" <eddie.dong@intel.com>,
	"Zhang, Xiantao" <xiantao.zhang@intel.com>
Subject: RE: TSC virtualization across different host frequency platform migration
Date: Wed, 22 Apr 2009 16:49:43 +0800	[thread overview]
Message-ID: <9832F13BD22FB94A829F798DA4A8280501A7FC0827@pdsmsx503.ccr.corp.intel.com> (raw)
In-Reply-To: <C614904C.926F%keir.fraser@eu.citrix.com>

Keir Fraser wrote:
> On 22/04/2009 02:32, "Dong, Eddie" <eddie.dong@intel.com> 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