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Date: Mon, 26 Mar 2012 20:06:52 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com> Cc: Ingo Molnar <mingo@...e.hu>, Mike Galbraith <efault@....de>, Suresh Siddha <suresh.b.siddha@...el.com>, linux-kernel <linux-kernel@...r.kernel.org>, Paul Turner <pjt@...gle.com> Subject: Re: sched: Avoid SMT siblings in select_idle_sibling() if possible On Mon, 2012-03-26 at 23:05 +0530, Srivatsa Vaddagiri wrote: > > From what I can tell, the huge improvement in benchmark score is coming from > reduced latencies for its VM tasks. But if the machine is pegged latency should not impact throughput (since there's always work to do), so are you creating extra idle time some place? Are you running against lock-inversion in the vcpus? Or that tlb shootdown issue we had in the gang scheduling thread? Both are typically busy-wait time, which is of course harder to spot that actual idle time :/ Then again, reducing latency is good, so I don't object to that per-se, but that flips the question, why does it regress those other loads? The biggest regression came from tbench, wasn't that mostly a random number generator anyway? How stable are those results, do you have a variance measure on the results? -- 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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