[haiku] Re: Scheduler (was: Re: Re: Multi-track recording and compositing)
- From: Ingo Weinhold <ingo_weinhold@xxxxxx>
- To: haiku@xxxxxxxxxxxxx
- Date: Sun, 07 Jun 2009 15:48:20 +0200
On 2009-06-07 at 14:23:53 [+0200], Michael Lotz <mmlr@xxxxxxxx> wrote:
> Hi Cyan
>
> > I can reproduce the poor "system load" results on this R5 system
> > by enabling the HLT instruction, and leaving the processors idle.
> > In other words, calling HLT seems to require some time to let the
> > processor recover (maybe the first interrupt is dropped/delayed?)
> > Spinning all four cores in a loop, even at minimum priority,
> > defeats the HLT calls and eliminates the jitter (as does disabling
> > the HLT instruction in the kernel config file).
> >
> > I don't suppose this problem should crop up under Haiku, being so
> > different at the kernel level?
>
> Actually, see these test results, both are from an idle Haiku after
> boot on a 2.4GHz Quad Core:
[...]
> The twist is that the first one was all normal and in the second the
> HLT instruction was simply disabled. I could imagine that our current
> scheduling policy of scheduling threads on idle CPUs is responsible.
> Obviously it's a good idea to schedule on a core that's currently idle,
> but on the downside you have to "wake" that core from a halt state
> which seems to have a certain overhead attached to it. Further
> investigation would be nice.
A run with SMP disabled would be interesting. If the "core wake-up" theory
is right, the results should improve.
CU, Ingo
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