Re: TSC Timecounter and multi-core/SMP

From: David O'Brien <obrien_at_freebsd.org>
Date: Thu, 17 Apr 2008 17:35:16 -0700
On Tue, Apr 15, 2008 at 09:46:02AM +0100, David Malone wrote:
> On Mon, Apr 14, 2008 at 09:51:42PM -1000, Jeff Roberson wrote:
> > I think we should confirm whether this is the case with earlier opterson. 
> > I have seen two processors on the same die out of sync.
> 
> This can definitely happen according to this note from AMD, which
> someone posted a link to earlier in the thread:
> 
> 	http://lkml.org/lkml/2005/11/4/173
> 
> it can happen when you hlt one core, but don't hlt the other on
> some processors.

Actually that is something slightly different.  Even without HLT, RDTSC
on the two cores of a dual-core processor can be out of sync.  HLT can
affect the delta between the two cores.

-- 
-- David  (obrien_at_FreeBSD.org)
Received on Thu Apr 17 2008 - 22:35:33 UTC

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