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Date:      Wed, 6 Jul 2011 09:28:11 -0700
From:      Steve Kargl <sgk@troutmask.apl.washington.edu>
To:        "O. Hartmann" <ohartman@zedat.fu-berlin.de>
Cc:        FreeBSD Current <freebsd-current@freebsd.org>, arrowdodger <6yearold@gmail.com>, freebsd-questions@freebsd.org
Subject:   Re: Heavy I/O blocks FreeBSD box for several seconds
Message-ID:  <20110706162811.GA68436@troutmask.apl.washington.edu>
In-Reply-To: <4E147F54.40908@zedat.fu-berlin.de>
References:  <4E1421D9.7080808@zedat.fu-berlin.de> <CALH631=F4bSgNDE4w0qcXGMgGxZRRwCP9n-H4M0c%2B1UEaqWr7Q@mail.gmail.com> <4E147F54.40908@zedat.fu-berlin.de>

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On Wed, Jul 06, 2011 at 05:29:24PM +0200, O. Hartmann wrote:
> 
> I use SCHED_ULE on all machines, since it is supposed to be performing 
> better on multicore boxes, but there are lots of suggestions switching 
> back to the old SCHED_4BSD scheduler.
> 

If you are using MPI in numerical codes, then you want
to use SCHED_4BSD.  I've posted numerous times about ULE
and its very poor performance when using MPI.

http://lists.freebsd.org/pipermail/freebsd-hackers/2008-October/026375.html

-- 
Steve



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