Date: Wed, 6 Jul 2011 11:00:01 -0700 From: Steve Kargl <sgk@troutmask.apl.washington.edu> To: Poul-Henning Kamp <phk@phk.freebsd.dk> Cc: FreeBSD Current <freebsd-current@freebsd.org>, "Hartmann, O." <ohartman@zedat.fu-berlin.de>, arrowdodger <6yearold@gmail.com>, freebsd-questions@freebsd.org Subject: Re: Heavy I/O blocks FreeBSD box for several seconds Message-ID: <20110706180001.GA69157@troutmask.apl.washington.edu> In-Reply-To: <5080.1309971941@critter.freebsd.dk> References: <20110706170132.GA68775@troutmask.apl.washington.edu> <5080.1309971941@critter.freebsd.dk>
next in thread | previous in thread | raw e-mail | index | archive | help
On Wed, Jul 06, 2011 at 05:05:41PM +0000, Poul-Henning Kamp wrote: > In message <20110706170132.GA68775@troutmask.apl.washington.edu>, Steve Kargl w > rites: > > >I periodically ran the same type test in the 2008 post over the > >last three years. Nothing has changed. I even set up an account > >on one node in my cluster for jeffr to use. He was too busy to > >investigate at that time. > > Isn't this just the lemming-syncer hurling every dirty block over > the cliff at the same time ? I don't know the answer. Of course, having no experience in processing scheduling, I don't understand the question either ;-) AFAICT, it is a cpu affinity issue. If I launch n+1 MPI images on a system with n cpus/cores, then 2 (and sometimes 3) images are stuck on a cpu and those 2 (or 3) images ping-pong on that cpu. I recall trying to use renice(8) to force some load balancing, but vaguely remember that it did not help. > To find out: Run gstat and keep and eye on the leftmost column > > The road map for fixing that has been known for years... I'll keep this in mind, the next time I upgrade the cluster. It's currently running a Feb 10th vintage kernel, and is under fairly heavy use at the moment. -- Steve
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20110706180001.GA69157>