Messages in this thread | | | Date | Tue, 24 Apr 2012 22:56:03 +0530 | From | Srivatsa Vaddagiri <> | Subject | Re: [PATCH v1] sched: steer waking task to empty cfs_rq for better latencies |
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* Peter Zijlstra <peterz@infradead.org> [2012-04-24 19:09:14]:
> On Tue, 2012-04-24 at 18:58 +0200, Peter Zijlstra wrote: > > On Tue, 2012-04-24 at 22:26 +0530, Srivatsa Vaddagiri wrote: > > > Steer a waking task towards a cpu where its cgroup has zero tasks (in > > > order to provide it better sleeper credits and hence reduce its wakeup > > > latency). > > > > That's just vile.. pjt could you post your global vruntime stuff so > > vatsa can have a go at that? > > That is, you're playing a deficiency we should fix, not exploit. > > Also, you do a second loop over all those cpus right after we've already > iterated them..
The first loop doesn't necessarily iterate thr' all cpus (as its looking for a core that is fully idle - and hence breaks once it finds a busy sibling).
> furthermore, that 100%+ gain is still way insane, what else is broken?
?
I have tried most benchmarks that were recommended for this kind of change. Let me know if you suggest any other benchmark ..
> Did you try those paravirt tlb-flush patches and other such weirdness?
I will try that next. But IMHO the benefit of reduced wakeup latencies should be over and above any benefit we get from paravirtualization.
- vatsa
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