Messages in this thread | | | Date | Mon, 02 Jan 2006 10:15:43 +0100 | From | Mike Galbraith <> | Subject | Re: [SCHED] wrong priority calc - SIMPLE test case |
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At 12:39 PM 1/1/2006 +0100, Paolo Ornati wrote: >On Sat, 31 Dec 2005 17:37:11 +0100 >Mike Galbraith <efault@gmx.de> wrote: > > > Strange. Using the exact same arguments, I do see some odd bouncing up to > > high priorities, but they spend the vast majority of their time down at 25. > >Mmmm... to make it more easly reproducible I've enlarged the sleep time >(1 microsecond is likely to be rounded too much and give different >results on different hardware/kernel/config...). > >Compile this _without_ optimizations and try again:
<snip>
>Try different values: 1000, 2000, 3000 ... are you able to reproduce it >now?
Yeah. One instance running has to sustain roughly _95%_ cpu before it's classified as a cpu piggy. Not good.
>If yes, try to start 2 of them with something like this: > >"./a.out 3000 & ./a.out 3161" > >so they are NOT syncronized and they use almost all the CPU time: > > PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND > 5582 paolo 16 0 2396 320 252 S 45.7 0.1 0:05.52 a.out > 5583 paolo 15 0 2392 320 252 S 45.7 0.1 0:05.49 a.out > >This is the bad situation I hate: some cpu-eaters that eat all the CPU >time BUT have a really good priority only because they sleeps a bit.
Yup, your proggy fools the interactivity estimator quite well. This problem was addressed a long time ago, and thought to be more or less cured. Guess not.
-Mike
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