RE: [patch] sched: auto-tune migration costs [was: Re: Industry db benchmark result on recent 2.6 kernels]

[Chen, Kenneth W]

Ingo Molnar wrote on Sunday, April 03, 2005 11:24 PM

> great! How long does the benchmark take (hours?), and is there any way
> to speed up the benchmarking (without hurting accuracy), so that
> multiple migration-cost settings could be tried? Would it be possible to
> try a few other values via the migration_factor boot option, in 0.5 msec
> steps or so, to find the current sweet spot? It used to be at 11 msec
> previously, correct?

It take days, each experiment is 5 hours.  Previous experiments on 2.6.8
shows that the sweet spot was 12.5ms.

This time on 2.6.11, it got pushed into 16 ms.  Results comparing to 10ms:

 8 ms  -0.3%
10 ms  --
12 ms	+0.11%
16 ms +0.14%
20 ms +0.06%

12ms and up all has about 1.5% idle time.  We are not anywhere near the
limits on what the disk storage can deliver.  So there is a potential to
to tune/optimize the scheduler and reap these extra idle time.

- Ken


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