Another message from Mikhail Kuzminsky, who for some reason or other cannot currently post directly to the list:
BEGIN FORWARD 1st of all, I should mention that the effect is observed only for Opteron 2350/OpenSuSE 10.3. Execution of the same job w/the same binaries on Nehalem E5520/OpenSuSe 11.1 gives the same time for 1 and 2 simultaneously runnung jobs. Mon, 23 May 2011 12:32:33 -0700 пиÑÑмо Ð¾Ñ "David Mathog" <mat...@caltech.edu>: > Mon, 23 May 2011 09:40:13 -0700 ÿøÃÂÃÂüþ þà"David Mathog" > <mat...@caltech.edu>: > > > On Fri, May 20, 2011 at 02:26:31PM -0400, Mark Hahn forwarded a message: > > > > When I run 2 identical examples of the same batch job > > simultaneously, execution time of *each* job is > > > > LOWER than for single job run ! > I thought also about cpus frequency variations, but I think that null output > of > lsmod|grep freq > is enough for fixed CPU frequency. > > END FORWARD > Regarding the frequencies, better to use > cat /proc/cpuinfo | grep MHz I looked to cpuinfo, but only manually - some times (i.e. I didn't run any script w/periodical looking for CPU frequencies). All the frequencies of cores were fixed. > Did you verify that the results for each of the two simultaneous runs > are both correct? Yes, the results are the same. I looked also to number of iterations etc. But I'll check outputs again. >Ideally, tweak some parameter so they are slightly > different from each other. But I don't understand - if I change slightly some of input parameters, what may it give ? > David Mathog > mat...@caltech.edu > Manager, Sequence Analysis Facility, Biology Division, Caltech Fri, 20 May 2011 20:11:15 -0400 message from Serguei Patchkovskii <serguei.patchkovs...@gmail.com>: > Suse 10.3 is quite old; it uses a kernel which is less than perfect at scheduling jobs and allocating resources for >NUMA systems. Try running your test job using: > > numactl --cpunodebind=0 --membind=0 g98 numactl w/all things bound to node 1 gives "big" execution time ( 1 day 4 hours; 2 simultaneous jobs run faster), for forcing different nodes for cpu and memory - execution time is even higher (+1 h). Therefore effect observed don't looks as result of numa allocations :-( Mikhail END FORWARD My point about the two different parameter sets on the jobs was to determine if the two were truly independent, or if they might not be interacting with each other through checkpoint files or shared memory, or the like. Regards, David Mathog mat...@caltech.edu Manager, Sequence Analysis Facility, Biology Division, Caltech _______________________________________________ Beowulf mailing list, Beowulf@beowulf.org sponsored by Penguin Computing To change your subscription (digest mode or unsubscribe) visit http://www.beowulf.org/mailman/listinfo/beowulf
