linux-kernel - Re: [PATCH] Skip tsc synchronization checks if CONSTANT

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Date:	Wed, 22 Oct 2008 22:17:43 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Alok Kataria <akataria@...are.com>,
	Andi Kleen <andi@...stfloor.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	LKML <linux-kernel@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	Daniel Hecht <dhecht@...are.com>
Subject: Re: [PATCH] Skip tsc synchronization checks if CONSTANT_TSC bit is set.

> the sync check is there to check the _offset_ between CPUs. CONSTANT_TSC 
> is not a guarantee that the TSC will be coherent across all CPUs.

I cannot find a quote for it in the docs now, but iirc the AMD 
definition of the bit guarantees offset, aka full synchronization
over the system.

-Andi
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