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SubjectRe: boot time, process start time, and NOW time
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On Mon, 2004-08-16 at 16:24, Albert Cahalan wrote:
> On Mon, 2004-08-16 at 15:41, Andrew Morton wrote:
>
> > Where did this all end up? Complaints about
> > wandering start times are persistent, and it'd
> > be nice to get some fix in place...
>
> If you're interested in reducing (not solving)
> the problem for the 2.6.x series, you might change
> HZ to something that works better with the PIT.
>
> Here is a table showing % error for various HZ choices:
>
> wrongness_% HZ_diff PIT_# HZ actual_HZ
> -0.00150855 -0.001509 11932 100 99.998491
> -0.00150855 -0.009474 1900 628 627.990526
> -0.00083809 -0.003051 3278 364 363.996949
> -0.00083809 -0.008389 1192 1001 1000.991611
> +0.00000000 +0.000000 14551 82 82.000000
> +0.00008381 +0.000304 3287 363 363.000304
> +0.00008381 +0.000435 2299 519 519.000435
> +0.00008381 +0.000525 1903 627 627.000525
> +0.01525566 +0.152557 1193 1000 1000.152557
> +0.01860917 +0.190558 1165 1024 1024.190558
>
> As you can see, 1000 HZ and 1024 HZ are really bad.
> They're worse than typical quartz crystal variation.
>
> The old 100 HZ tick was just barely tolerable.
> While 82 is perfect, it's a bit low. :-(
>
> Some of the other choices are nice. How about 363,
> 519, or 627?

What about 1001? That looks reasonably accurate.

thanks
-john


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