Messages in this thread | | | Date | Tue, 17 Mar 2009 09:12:55 -0400 | From | Paul Gortmaker <> | Subject | Re: [Patch] Fix the possibility of insane return value of hpet_calibrate() against SMI. |
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Yasunori Goto wrote: > Sorry for late response. > > >> Yasunori Goto wrote: >> >>>> I've no sense of feel for how long each calibration run would take. >>>> Would doing it 5 times show up as a significant increase in the boot >>>> time for those that care about boot time being as quick as possible? >>>> >>> Hmm. The loop times is trade off against reliable value.... >>> Though SMI is rare interruption, I don't know how frequent >>> hypervisor's switch is. >>> >> Could you, just for testing, run the calibration five thousand times or >> so instead of five times, and count how often you get insane values? >> (And how much delay does such an SMI add?) >> > > I tried 50000 times. But insane value was nothing. > I think SMI is very rare. > > >>> Each calibration of this has 1 milli second. >>> Do you think 5 msec is too long? >>> >> This shouldn't matter when booting. Anyway, I think it's possible to >> increase TICK_CALIBRATE without losing too much accuracy. >> > > Hmm. If the person who is trying to reduce boot time for fastboot dislikes this impact, > then I'll try Vojtech-san's way. >
That probably makes sense -- if it is extremely rare, and if you get two values that are the same (within some small delta) then you probably are 99.99% confident that you have the right data.
Paul.
> > Thanks. >
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