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SubjectRe: [PATCH] self tuning scheduler
At 06:04 PM 3/11/2003 -0500, Jim Houston wrote:
>Hi Mike
>
>I made a bit of progress on understanding the irman problem with
>my scheduler change. When I run irman and top, the processes end
>up with priorities like:
>
> irman parent 36
> irman child 21
> process_child 31-33 (group of 9 processes)
>
>Since I expanded the range of priorities (to 0-79) these are quite
>favorable priorities. They are all have MAX_SLEEP_AVG bonus
>equivelent of nice +10.
>
>It's a priority inversion problem. The irman child is waiting for
>a read. The process_child processes are happly running as a group
>at approximately the same priority. The irman parent is starved
>because it is at a lower priority. It is at a lower priority because
>it uses more cpu on each pass. It is doing the gettimeofday calls
>while the child only does the pipe read & write. The parent gets
>an occasional boost from the fairness_update() code so it doesn't
>totally starve.

I forgot to mention something odd I encountered wrt the parent's
priority. I can set the irman child SCHED_RR, and it shows up in top with
priority -2. The parent remains at priority 36 and remains starved. Max
renice doesn't help either.

-Mike

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