Date: Wed, 14 Dec 2011 11:59:51 -0500 From: Mike Tancsa <mike@sentex.net> To: mdf@freebsd.org Cc: Ivan Klymenko <fidaj@ukr.net>, Doug Barton <dougb@freebsd.org>, freebsd-stable@freebsd.org, Jilles Tjoelker <jilles@stack.nl>, "O. Hartmann" <ohartman@mail.zedat.fu-berlin.de>, Current FreeBSD <freebsd-current@freebsd.org>, freebsd-performance@freebsd.org Subject: Re: SCHED_ULE should not be the default Message-ID: <4EE8D607.1000504@sentex.net> In-Reply-To: <CAMBSHm89SkzGVgk9kNwBQoR62pXKjhJ%2BqXJK0qwC20r9p%2Bu-bw@mail.gmail.com> References: <4EE1EAFE.3070408@m5p.com> <4EE22421.9060707@gmail.com> <4EE6060D.5060201@mail.zedat.fu-berlin.de> <4EE69C5A.3090005@FreeBSD.org> <20111213104048.40f3e3de@nonamehost.> <20111213230441.GB42285@stack.nl> <4ee7e2d3.0a3c640a.4617.4a33SMTPIN_ADDED@mx.google.com> <CAMBSHm89SkzGVgk9kNwBQoR62pXKjhJ%2BqXJK0qwC20r9p%2Bu-bw@mail.gmail.com>
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On 12/13/2011 7:01 PM, mdf@freebsd.org wrote:
>
> Has anyone experiencing problems tried to set sysctl kern.sched.steal_thresh=1 ?
>
> I don't remember what our specific problem at $WORK was, perhaps it
> was just interrupt threads not getting serviced fast enough, but we've
> hard-coded this to 1 and removed the code that sets it in
> sched_initticks(). The same effect should be had by setting the
> sysctl after a box is up.
FWIW, this does impact the performance of pbzip2 on an i7. Using a 1.1G file
pbzip2 -v -c big > /dev/null
with burnP6 running in the background,
sysctl kern.sched.steal_thresh=1
vs
sysctl kern.sched.steal_thresh=3
N Min Max Median Avg Stddev
x 10 38.005022 38.42238 38.194648 38.165052 0.15546188
+ 9 38.695417 40.595544 39.392127 39.435384 0.59814114
Difference at 95.0% confidence
1.27033 +/- 0.412636
3.32852% +/- 1.08119%
(Student's t, pooled s = 0.425627)
a value of 1 is *slightly* faster.
--
-------------------
Mike Tancsa, tel +1 519 651 3400
Sentex Communications, mike@sentex.net
Providing Internet services since 1994 www.sentex.net
Cambridge, Ontario Canada http://www.tancsa.com/
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