Uninformed Comment

CPU symmetry

Posted in OpenSim, Technology by uninformedcomment on March 14, 2010

System monitor CPU graph, showing two CPUs balanced in a pretty way

Ubuntu’s System Monitor demonstrates a fairness and sense of balance on the part of the CPU scheduler that’s almost pretty And only when it’s doing this one task, too. I don’t know why.

(It’s not actually a dual CPU system – it’s a Pentium 4, so the CPU split is virtual. The task being run there is an LSL script in OpenSim , doing some heavy manipulation of large lists.)

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  1. Eben King said, on August 4, 2010 at 5:08 pm

    I think what’s happening here is you have one big process that uses ~40% of the CPU (high_line – low_line) and some smaller processes that make up the rest. The scheduler occasionally moves the big one between CPU1 and CPU2 for whatever reason, and the lines switch places.

    • uninformedcomment said, on August 4, 2010 at 6:52 pm

      Yes, that sounds like what’s going on. The mystery to me, though, is why the scheduler changes the allocation like that; it’s not as if the switches are evenly-spaced, or occur only at peaks, or anything like that.

      Also I’m puzzled why the two (sets of) processes are complementary in that mirror-effect manner, like a mountain range reflected in a calm lake. Oh, the poetry …

      Incidentally, I have noticed this pattern since writing that post, and under completely different circumstances than the LSL/OpenSim context mentioned, so it seems not to be a characteristic only of that particular situation.

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