Date: Mon, 15 Sep 2008 20:34:59 -0700 From: Steve Kargl <sgk@troutmask.apl.washington.edu> To: Stephen Montgomery-Smith <stephen@math.missouri.edu> Cc: Martin Cracauer <cracauer@cons.org>, freebsd-current@freebsd.org Subject: Re: Improved multiprocessor usage on amd64 Message-ID: <20080916033459.GA31220@troutmask.apl.washington.edu> In-Reply-To: <48CEFF74.8020602@math.missouri.edu> References: <48CDBC78.4010409@math.missouri.edu> <20080915195021.GA69528@cons.org> <48CEFF74.8020602@math.missouri.edu>
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On Mon, Sep 15, 2008 at 07:36:04PM -0500, Stephen Montgomery-Smith wrote:
>
> ... and each thread is a loop of the form
>
> while (1) {
> wait until told to start;
> do massive amounts of floating point arithmetic (only additions and
> multiplications) on large arrays;
> tell the master process that you are done;
> }
>
> >Do you have about as many threads as processor or more?
>
> Both ways. The time difference between the two approaches is negligible.
>
Are you using ULE? With my MPI applications, if the number of
launched processes exceeds the number of cpus by 1, ULE falls
through the floor. I have a nagging feeling that there is
a problem with cpu affinity.
http://lists.freebsd.org/pipermail/freebsd-current/2008-July/086917.html
--
Steve
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