Messages in this thread | | | Date | Thu, 04 Sep 2008 15:18:35 -0000 | From | Thomas Gleixner <> | Subject | [RFC patch 0/4] TSC calibration improvements |
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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.
Thanks,
tglx --
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