Re: [RFC PATCH 00/11] sched: CFS low-latency features

Mathieu Desnoyers
2010-08-27T18:38:33Z

* Mathieu Desnoyers (mathieu.desnoyers@efficios.com) wrote:
> * Mike Galbraith (efault@gmx.de) wrote:
> > On Fri, 2010-08-27 at 09:42 +0200, Peter Zijlstra wrote:
> > > On Thu, 2010-08-26 at 19:49 -0400, Mathieu Desnoyers wrote:
> > > > AFAIK, I don't think we would end up starving the system in any possible way.
> > >
> > > Correct, it does maintain fairness.
> > >
> > > > So far I cannot see a situation where selecting the next buddy would _not_ make
> > > > sense in any kind of input-driven wakeups (interactive, timer, disk, network,
> > > > etc). But maybe it's just a lack of imagination on my part.
> > >
> > > The risk is that you end up with always using next-buddy, and we tried
> > > that a while back and that didn't work well for some, Mike might
> > > remember.
> >
> > I turned it off because it was ripping spread apart badly, and last
> > buddy did a better job of improving scalability without it.
>
> Maybe with the dyn min_vruntime feature proposed in this patchset we should
> reconsider this. Spread being ripped apart is exactly what it addresses.

I'm curious: which workload was showing this kind of problem exactly ?

Thanks,

Mathieu

--
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.