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From: "Nish Aravamudan" <firstname.lastname@example.org> To: "Bill Davidsen" <email@example.com> Cc: "Paulo Marques" <firstname.lastname@example.org>, "Rik van Riel" <email@example.com>, "J.A. Magallón" <firstname.lastname@example.org>, "Hiro Yoshioka" <email@example.com>, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com, firstname.lastname@example.org, email@example.com Subject: Re: SMP performance degradation with sysbench Date: Wed, 28 Feb 2007 16:20:54 -0800 [thread overview] Message-ID: <firstname.lastname@example.org> (raw) In-Reply-To: <email@example.com> [-- Attachment #1: Type: text/plain, Size: 2012 bytes --] On 2/27/07, Nish Aravamudan <firstname.lastname@example.org> wrote: > On 2/27/07, Bill Davidsen <email@example.com> wrote: > > Paulo Marques wrote: > > > 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. <snip> > > > If that is the case, turning off CONFIG_SCHED_SMT would solve the problem. <snip> > > Note that Intel does make multicore HT processors, and hopefully when > > this code works as intended it will result in more total throughput. My > > supposition is that it currently is NOT working as intended, since > > disabling SMT scheduling is reported to help. > > It does help, but we still drop off, clearly. Also, that's my > baseline, so I'm not able to reproduce the *sharp* dropoff from the > blog post yet. > > > A test with MC on and SMT off would be informative for where to look next. > > I'm rebooting my box with 220.127.116.11 and exactly this setup now. Here are the results: idle.png: average % idle over 120s runs from 1 to 32 threads transactions.png: TPS over 120s runs from 1 to 32 threads Hope the data is useful. All I can conclude right now is that SMT appears to help (contradicting what I said earlier), but that MC seems to have no effect (or no substantial effect). Thanks, Nish [-- Attachment #2: idle.png --] [-- Type: image/png, Size: 5482 bytes --] [-- Attachment #3: transactions.png --] [-- Type: image/png, Size: 6653 bytes --]
next prev parent reply other threads:[~2007-03-01 0:20 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 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 [this message] 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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