Messages in this thread | | | Date | Thu, 13 Aug 2009 17:58:12 +0200 | From | Andreas Mohr <> | Subject | Re: CPU scheduler weirdness? |
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Hi,
On Thu, Aug 13, 2009 at 05:39:10PM +0200, Marton Balint wrote: >>> Does anybody have any idea what can cause this? >> >> /sys/devices/system/cpu/sched_smt_power_savings , perhaps? > > Thanks for the tip, tuning the sched_mc_power_savings setting helped! The > original value of it was 0, but after setting it to 1, the two > cpu-intensive processes got scheduled to different CPU cores, as > expected.
Heh, I did expect it to not help, and indeed that thing helping in this way points to a... BUG, plain and simple.
http://lwn.net/Articles/297306/ lists possible settings as
" The power savings and performance of the given workload in an under utilised system can be controlled by setting values of 0, 1 or 2 to /sys/devices/system/cpu/sched_mc_power_savings with 0 being highest performance and least power savings and level 2 indicating maximum power savings even at the cost of slight performance degradation. "
which is exactly opposite to what I'd have expected to be normal, unconfigured behaviour in your case.
> Setting it back to 0 casused the two cpu-intensive processes to run on > the same CPU again. So I guess I will just set it to 1 after booting the > system.
...which would indicate a level=1 or level=2 (maximum powersaving) behaviour. Something either seems reversed or really weird. But it could just be opaque if correct behaviour due to a much more complex load balancing algo in the scheduler or so.
Comments, anyone?
Andreas Mohr
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