From: Andi Kleen <ak@suse.de>
To: Jonas Oreland <jonas@mysql.com>
Subject: Re: x86-64: Syncing dualcore cpus TSCs
Date: Tue, 25 Oct 2005 09:42:25 +0200
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       Andrew Morton <akpm@osdl.org>, discuss@x86-64.org
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On Tuesday 25 October 2005 09:35, Jonas Oreland wrote:
> Hi,
>
> This might be a very bad suggestion, but here it is:
>
> On dualcore cpus (amd64) the TSC will get out of sync when executing hlt
> instruction. booting with idle=poll, will make it never to execute hlt,
> hence TSC will be in sync. booting with notsc will make it use other time
> source...but this is slower (this is default after "[PATCH] x86-64: Fix bad
> assumption that dualcore cpus have synced TSCs")
>
> How about syncing TSC after hlt?
>
> If cost of syncing TSC's is smaller than cost of using other time source
> this might be an alternative.

I very doubt it is. Syncing TSCs requires stopping multiple CPUs for longer 
time. It is unlikely you can make that up.

-Andi
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