Re: [PATCH RFC] smt nice introduces significant lock contention

[Con Kolivas]

On Friday 02 June 2006 18:28, Nick Piggin wrote:
> Con Kolivas wrote:
> > On Friday 02 June 2006 17:53, Nick Piggin wrote:
> >>This is a small micro-optimisation / cleanup we can do after
> >>smtnice gets converted to use trylocks. Might result in a little
> >>less cacheline footprint in some cases.
> >
> > It's only dependent_sleeper that is being converted in these patches. The
> > wake_sleeping_dependent component still locks all runqueues and needs to
>
> Oh I missed that.
>
> > succeed in order to ensure a task doesn't keep sleeping indefinitely.
> > That
>
> Let's make it use trylocks as well. wake_priority_sleeper should ensure
> things don't sleep forever I think? We should be optimising for the most
> common case, and in many workloads, the runqueue does go idle frequently.

wake_priority_sleeper is only called per tick which can be 10ms at 100HZ. I 
don't think that's fast enough. It could even be possible for a lower 
priority task to always just miss the wakeup if it's (very) unlucky.

-- 
-ck
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