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Date: Sat, 5 Sep 2009 17:47:39 -0700 From: Anirban Sinha <ani@...rban.org> To: linux-kernel@...r.kernel.org, fchecconi@...il.com, Ingo Molnar <mingo@...e.hu>, a.p.zijlstra@...llo.nl Cc: Anirban Sinha <ASinha@...gmasystems.com>, Anirban Sinha <ani@...rban.org> Subject: Re: question on sched-rt group allocation cap: sched_rt_runtime_us > You say you pin the threads to a single core: how many cores does your > system have? The results I sent you were on a dual core blade. > If this is the case, this behavior is the expected one, the scheduler > tries to reduce the number of migrations, concentrating the bandwidth > of rt tasks on a single core. With your workload it doesn't work well > because runtime migration has freed the other core(s) from rt bandwidth, > so these cores are available to SCHED_OTHER ones, but your SCHED_OTHER > thread is pinned and cannot make use of them. But, I ran the same routine on a quadcore blade and the results this time were: rt_runtime/rt_period % of iterations of reg thrd against rt thrd 0.20 46% 0.25 18% 0.26 7% 0.3 0% 0.4 0% (rest of the cases) 0% So if the scheduler is concentrating all rt bandwidth to one core, it should be effectively 0.2 * 4 = 0.8 for this core. Hence, we should see the percentage closer to 20% but it seems that it's more than double. At ~0.25, the regular thread should make no progress, but it seems it does make a little progress. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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