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SubjectRe: [patch 4/9] Remove the TSC synchronization on SMP machines
On Thu, Feb 01, 2007 at 02:17:15PM +0100, Jiri Bohac wrote:
> On Thu, Feb 01, 2007 at 12:14:23PM +0100, Andi Kleen wrote:
> > On Thursday 01 February 2007 10:59, jbohac@suse.cz wrote:
> > > TSC is either synchronized by design or not reliable
> > > to be used for anything, let alone timekeeping.
> >
> > In my tree this is already done better by a patch from Ingo.
> > Check if they look synchronized and don't use TSC if they are not.
>
> The whole purpose of this patchset is to make use of TSC even if
> it's not synchronized.
>
> Synchronizing it will not make anything better in any way -- the
> implementation just does not care whether TSCs are synchronized.
> That's why I think the synchronization code is not needed.

It might even make sense to desycnhronize the TSCs on such (AMD)
machines on purpose, so that applications that rely on TSC break
immediately and not after some time when the error becomes too large.

--
Vojtech Pavlik
Director SuSE Labs
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