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From: Paulo Marques <pmarques@grupopie.com> To: Rik van Riel <riel@redhat.com> Cc: "\"J.A. Magallón\"" <jamagallon@ono.com>, "Hiro Yoshioka" <hyoshiok@miraclelinux.com>, davej@redhat.com, harlan@artselect.com, nickpiggin@yahoo.com.au, l_allegrucci@yahoo.it, linux-kernel@vger.kernel.org, mingo@elte.hu, suparna@in.ibm.com, jens.axboe@oracle.com Subject: Re: SMP performance degradation with sysbench Date: Tue, 27 Feb 2007 14:56:28 +0000 [thread overview] Message-ID: <45E4469C.8000505@grupopie.com> (raw) In-Reply-To: <45E439E4.5030703@redhat.com> Rik van Riel wrote: > J.A. Magallón wrote: >>[...] >> Its the same to answer 4+4 queries than 8 at half the speed, isn't it ? > > That still doesn't fix the potential Linux problem that this > benchmark identified. > > To clarify: I don't care as much about MySQL performance as > I care about identifying and fixing this potential bug in > Linux. IIRC a long time ago there was a change in the scheduler to prevent a low prio task running on a sibling of a hyperthreaded processor to slow down a higher prio task on another sibling of the same processor. Basically the scheduler would put the low prio task to sleep during an adequate task slice to allow the other sibling to run at full speed for a while. I don't know the scheduler code well enough, but comments like this one make me think that the change is still in place: > /* > * If an SMT sibling task has been put to sleep for priority > * reasons reschedule the idle task to see if it can now run. > */ > if (rq->nr_running) { > resched_task(rq->idle); > ret = 1; > } If that is the case, turning off CONFIG_SCHED_SMT would solve the problem. -- Paulo Marques - www.grupopie.com "The face of a child can say it all, especially the mouth part of the face."
next prev parent reply other threads:[~2007-02-27 14:56 UTC|newest] Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top 2007-02-25 17:44 SMP performance degradation with sysbench Lorenzo Allegrucci 2007-02-25 23:46 ` Rik van Riel 2007-02-26 13:36 ` Nick Piggin 2007-02-26 13:41 ` Nick Piggin 2007-02-26 22:04 ` Pete Harlan 2007-02-26 22:36 ` Dave Jones 2007-02-27 0:32 ` Hiro Yoshioka 2007-02-27 0:43 ` Rik van Riel 2007-02-27 4:03 ` Hiro Yoshioka 2007-02-27 4:31 ` Rik van Riel 2007-02-27 8:14 ` J.A. Magallón 2007-02-27 14:02 ` Rik van Riel 2007-02-27 14:56 ` Paulo Marques [this message] 2007-02-27 20:40 ` Nish Aravamudan 2007-02-28 2:21 ` Bill Davidsen 2007-02-28 2:52 ` Nish Aravamudan 2007-03-01 0:20 ` Nish Aravamudan 2007-02-27 19:05 ` Lorenzo Allegrucci 2007-03-01 16:57 ` Lorenzo Allegrucci 2007-02-28 1:27 ` Nish Aravamudan 2007-02-28 2:22 ` Nick Piggin 2007-02-28 2:51 ` Nish Aravamudan 2007-03-12 22:00 ` Anton Blanchard 2007-03-13 5:11 ` Nick Piggin 2007-03-13 9:45 ` Andrea Arcangeli 2007-03-13 10:06 ` Nick Piggin 2007-03-13 10:31 ` Andrea Arcangeli 2007-03-13 10:37 ` Nick Piggin 2007-03-13 10:57 ` Andrea Arcangeli 2007-03-13 11:12 ` Nick Piggin 2007-03-13 11:40 ` Eric Dumazet 2007-03-13 11:56 ` Nick Piggin 2007-03-13 11:42 ` Andrea Arcangeli 2007-03-13 12:02 ` Eric Dumazet 2007-03-13 12:27 ` Jakub Jelinek 2007-03-13 12:08 ` Nick Piggin 2007-03-14 23:33 ` Siddha, Suresh B 2007-03-20 2:29 ` Zhang, Yanmin 2007-04-02 2:59 ` Zhang, Yanmin 2007-03-13 6:00 ` Eric Dumazet 2007-03-14 0:36 ` Nish Aravamudan 2007-03-14 1:00 ` Eric Dumazet 2007-03-14 1:09 ` Nish Aravamudan [not found] <fa.V3M3ZgXL+lFlIyhx43YxCU/JFUk@ifi.uio.no> [not found] ` <fa.ciL5lzdfskdJHJPgn+UVCHt/9EM@ifi.uio.no> [not found] ` <fa.2ABbHhyCbp3Fx7hSE/Gr0SuzFvw@ifi.uio.no> [not found] ` <fa.oaZk6Aiqd8gyZNsj7+m+w9MibhU@ifi.uio.no> [not found] ` <fa.RjX9Y4ckjRCle5L+uWNdd0snOio@ifi.uio.no> [not found] ` <fa.XocsudxlGplKh0kloTtA0juPwtA@ifi.uio.no> 2007-02-28 0:20 ` Robert Hancock 2007-02-28 1:32 ` Hiro Yoshioka
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