Re: [git pull] scheduler fixes

Matthew Wilcox
2008-05-11T15:30:16Z

On Sun, May 11, 2008 at 05:19:09PM +0200, Ingo Molnar wrote:
> * Matthew Wilcox <matthew@wil.cx> wrote:
> > > exactly what usecase is that? Perhaps it could be converted to an
> > > atomic counter + the wait_event() APIs.
> >
> > Effectively, it's a completion. It just works better with staggered
> > wakeups than it does with the naive completion.
>
> So why not transform it to real completions instead? And if our current
> 'struct completion' abstraction is insufficient for whatever reason, why
> not extend that instead?

My point is that for the only user of counting semaphores and/or
semaphores-abused-as-completions that has so far hit this race, the
serialised wake-up performs better. You have not pointed at a scenario
that _shows_ a parallel wake-up to perform better. Some hand-waving
and talking about lofty principles, yes. But no actual data.

--
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"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
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