Messages in this thread | | | Subject | Re: [rfc][patch] select_idle_sibling() inducing bouncing on westmere | From | Mike Galbraith <> | Date | Sun, 27 May 2012 16:32:02 +0200 |
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On Sun, 2012-05-27 at 16:29 +0200, Mike Galbraith wrote: > On Sun, 2012-05-27 at 07:11 -0700, Arjan van de Ven wrote: > > On 5/27/2012 2:17 AM, Mike Galbraith wrote: > > > On Sat, 2012-05-26 at 10:27 +0200, Mike Galbraith wrote: > > >> Hohum, back to finding out what happened to cpufreq. > > > > > > Answer: nothing.. in mainline. > > > > > > I test performance habitually, so just never noticed how bad ondemand > > > sucks. In enterprise, I found the below, explaining why cores crank up > > > fine there, but not in mainline. Somebody thumped ondemand properly on > > > it's pointy head. > > > > > > But, check out the numbers below this, and you can see just how horrible > > > bouncing is when you add governor latency _on top_ of it. > > > > part of it is not ondemand, but cpufreq. > > cpufreq forces you to schedule a kernel thread to change cpu > > frequency... on the cpu that's already busy. > > God knows what the scehduler then does in terms of load balancing.
(and yeah, I am lumping ondemand and cpufreq together, which is wrong)
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