Re: [PATCH] x86-64: Fix bad assumption that dualcore cpus havesynced TSCs

[john stultz]

On Mon, 2005-09-19 at 21:31 +0200, Andi Kleen wrote:
> On Mon, Sep 19, 2005 at 12:16:43PM -0700, john stultz wrote:
> > 	This patch should resolve the issue seen in bugme bug #5105, where it
> > is assumed that dualcore x86_64 systems have synced TSCs. This is not
> > the case, and alternate timesources should be used instead.
> 
> 
> I asked AMD some time ago and they told me it was synchronized.
> The TSC on K8 is C state invariant, but not P state invariant,
> but P states always happen synchronized on dual cores.
> 
> So I'm not quite convinced of your explanation yet.

Would a litter userspace test checking the TSC synchronization maybe
shed additional light on the issue?

thanks
-john



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