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[20161222] Bringing the scheduler saga to the finishing line
After my last blog postings on the NetBSD scheduler, some time went by. What has happened that the code to handle process migration was rewritten to give more knobs for tuning, and some testing was done. The initial problem state in PR kern/51615 is solved by the code. To reach a wider audience and get more testing, the code was committed to NetBSD-current today.

Now, two things remain to be seen:

  1. More testing. This best involved situations that compare the system's behaviour without and with the patch. Situations to test include
    • pure computation jobs that involve multiple parallel processes
    • a mix of CPU-crunching and input/output, again on a number of concurrent processes
    • full build.sh examples
    If you have time and an interesting set of numbers, please feel free to let us know on tech-kern@..

  2. Documentation. There is already a number of undocumented sysctls under "kern.sched", which was now extended by one more, "average_weight". While it's obvious to add the knob from the formula, testing it under various real-life conditions and see how things change is left to be determined by a PhD thesis or two - be sure to drop us your patches for src/share/man/man7/sysctl.7 if you can come up with a comprehensible description of all the scheduler sysctls!
So just now when you thought there is no more research to be done in scheduling algorithms, here is your chance to fame and glory! :-)

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