Messages in this thread |  | | | Date | Thu, 4 Sep 2008 17:36:20 +0200 | | From | Ingo Molnar <> | | Subject | Re: [RFC patch 0/4] TSC calibration improvements |
* Thomas Gleixner <tglx@linutronix.de> wrote:
> This patch series addresses following:> > - reduce the calibration time to a useful value
> - make decision smarter, when a reference (HPET/PMTIMER) is around
>
> The first patches are cleanups to prepare for the smarter loop
> handling.
>
> The main change is to reduce the PIT delay value to 10ms, which gives
> reasonable results on very slow machines as well. To avoid looping
> several times when the machine has a working reference counter
> (HPET/pmtimer), we compare the results of the PIT and the reference and
> break out of the loop when both match inside of a 10% window.
>
> For virtualized environments the PIT calibration fails often and the
> reference calibration is not reproducible with 10ms. To address this
> we check whether the PIT failed two times in a row and make the PIT
> loop longer (50ms) for the last try to get a better result for the
> reference.
>
> Most of the machines I tested break out of the loop after the first
> try with a stable reproducible result.
i've added them to tip/x86/tsc and merged it into tip/master - if
there's test success we can merge it into x86/urgent as well and push it
into v2.6.27. Any objections to that merge route?
Ingo
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