[Beowulf] cpufreq, multiple cores, load

Guy Coates gmpc at sanger.ac.uk
Wed Mar 10 04:20:57 EST 2010


>> consumption.  Starting a second cpuburn apparently schedules it
>> on one of the cores on the unused second processor, rather than
>> on the equally unused, but already sped up, second core on the first
> 
> well, that's a kernel/scheduler choice, probably pretty hackable.
> or else just use numactl to direct the second cpuburn away from
> the second socket.  in fact, using numactl to control memory allocation
> would probably be a good idea anyway.
> 
You can change that schedular behaviour by twiddling sched_mc_power_savings

echo 1 > /sys/devices/system/cpu/sched_mc_power_savings


http://www.lesswatts.org/tips/cpu.php

"'sched_mc_power_savings' tunable under /sys/devices/system/cpu/
controls the Multi-core related tunable. By default, this is set to '0'
(for optimal performance). By setting this to '1', under light load
scenarios, the process load is distributed such that all the cores in a
processor package are busy before distributing the process load to other
processor packages."


Cheers,

Guy

-- 
Dr. Guy Coates,  Informatics System Group
The Wellcome Trust Sanger Institute, Hinxton, Cambridge, CB10 1HH, UK
Tel: +44 (0)1223 834244 x 6925
Fax: +44 (0)1223 496802


-- 
 The Wellcome Trust Sanger Institute is operated by Genome Research 
 Limited, a charity registered in England with number 1021457 and a 
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