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SubjectRe: [PATCH] x86 (64): make calibrate_APIC_clock() SMI-safe
H. Peter Anvin wrote:

> The other thing we may want to consider is doing multiple runs of the
> calibration loop. I suspect we'd get a more accurate result running,
> say, 9 loops of the 1/9 the current duration and looking either for the
> best result or the median (NOT the mean.)
>
> -hpa

We considered that. However I think if you know what result to expect
(here: TICK_COUNT + a few cycles) it is both easier and safer to compare
against the expected value than to do statistics. SMI protection is all
about outliers (thus, the median is a good suggestion but I'd say it
would be over-enigineered).

Martin

PS: I am sorry for the stupid, misleading typo (SMi -> smp) in the mail
subject.

--
Martin Wilck
PRIMERGY System Software Engineer
FSC IP ESP DEV 6

Fujitsu Siemens Computers GmbH
Heinz-Nixdorf-Ring 1
33106 Paderborn
Germany

Tel: ++49 5251 8 15113
Fax: ++49 5251 8 20209
Email: mailto:martin.wilck@fujitsu-siemens.com
Internet: http://www.fujitsu-siemens.com
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