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From: "Nish Aravamudan" <nish.aravamudan@gmail.com>
To: "Paulo Marques" <pmarques@grupopie.com>
Cc: "Rik van Riel" <riel@redhat.com>,
"\"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 12:40:45 -0800 [thread overview]
Message-ID: <29495f1d0702271240p1f446a74me9623ae756c67eb5@mail.gmail.com> (raw)
In-Reply-To: <45E4469C.8000505@grupopie.com>
On 2/27/07, Paulo Marques <pmarques@grupopie.com> 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.
>
> I don't know the scheduler code well enough, but comments like this one
> make me think that the change is still in place:
<snip>
> If that is the case, turning off CONFIG_SCHED_SMT would solve the problem.
To chime in here, I was attempting to reproduce this on an 8-way Xeon
box (4 dual-core). SCHED_SMT and SCHED_MC on led to scaling issues
when above 4 threads (4 threads was the peak). To the point, where I
couldn't break 1000 transactions per second. Turning both off (with
2.6.20.1) gives much better performance through 16 threads. I am now
running for the cases from 17 to 32 to see if I can reproduce the
problem at hand. I'll regenerate my data and post numbers soon.
I don't know if anyone else has those on in their kernel .config, but
I'd suggest turning them off, as Paulo said.
Thanks,
Nish
next prev parent reply other threads:[~2007-02-27 20:40 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-02-25 17:44 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 [this message]
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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