Date: Mon, 12 Dec 2011 13:03:30 -0600 From: Scott Lambert <lambert@lambertfam.org> To: Current FreeBSD <freebsd-current@freebsd.org>, freebsd-stable@freebsd.org, freebsd-performance@freebsd.org Subject: Re: SCHED_ULE should not be the default Message-ID: <20111212190330.GA69380@sysmon.tcworks.net> In-Reply-To: <20111212170604.GA74044@troutmask.apl.washington.edu> References: <4EE1EAFE.3070408@m5p.com> <4EE22421.9060707@gmail.com> <4EE6060D.5060201@mail.zedat.fu-berlin.de> <20111212155159.GB73597@troutmask.apl.washington.edu> <4EE6295B.3020308@cran.org.uk> <20111212170604.GA74044@troutmask.apl.washington.edu>
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On Mon, Dec 12, 2011 at 09:06:04AM -0800, Steve Kargl wrote: > Tuning kern.sched.preempt_thresh did not seem to help for > my workload. My code is a classic master-slave OpenMPI > application where the master runs on one node and all > cpu-bound slaves are sent to a second node. If I send > send ncpu+1 jobs to the 2nd node with ncpu's, then > ncpu-1 jobs are assigned to the 1st ncpu-1 cpus. The > last two jobs are assigned to the ncpu'th cpu, and > these ping-pong on the this cpu. AFAICT, it is a cpu > affinity issue, where ULE is trying to keep each job > associated with its initially assigned cpu. > > While one might suggest that starting ncpu+1 jobs > is not prudent, my example is just that. It is an > example showing that ULE has performance issues. > So, I now can start only ncpu jobs on each node > in the cluster and send emails to all other users > to not use those node, or use 4BSD and not worry > about loading issues. Does it meet your expectations if you start (j modulo ncpu) = 0 jobs on a node? -- Scott Lambert KC5MLE Unix SysAdmin lambert@lambertfam.org
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