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[Xen-devel] RE: [PATCH] clocksource=tsc

To: "Keir Fraser" <keir.fraser@xxxxxxxxxxxxx>, "Xen-Devel (E-mail)" <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: [Xen-devel] RE: [PATCH] clocksource=tsc
From: "Dan Magenheimer" <dan.magenheimer@xxxxxxxxxx>
Date: Tue, 15 Jul 2008 08:44:31 -0600
Cc: Dave Winchell <dwinchell@xxxxxxxxxxxxxxx>
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> Changeset 18055 is what I had in mind. I split out the
> read_counter-is-64-bit portion separately. The changeset 
> needs a bit of
> testing and it may need a tweak or two.

Hmmm... One thing I was trying to do with the special
casing in get_s_time() was to avoid using a dynamically
changing scaling (t->tsc_scale).  If I'm not mistaken,
t->tsc_scale is recalculated every EPOCH and thus is
a potential source of stime jitter.  Seems unnecessary
just to make the code look cleaner.

One other nit:  Especially if the above is changed, do
you really prefer a strcmp vs a global variable (or
checking for size == 64) for determining if the tsc
is the platform timer?

Thanks,
Dan


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