On Thu, Jan 13, 2022 at 06:17:54PM -0800, Jonathan Thornburg wrote:
> I've just noticed something odd about the scheduling of processes with
> varying 'nice' values (7.0-stable/amd64, GENERIC.MP): it appears that
> processes with 'nice 20' are given more favorable scheduling than those
> with 'nice 10', which is exactly the opposite of what I'd expect based
> on the man page for setpriority(2), "lower priorities cause more favorable
> scheduling" (and longstanding Unix experience).
>
> In more detail:
> Right now I have 5 CPU-bound processes running (all the same binary, but
> with different command-line arguments and started from different working
> directories), on hardware with 4 CPUs visible to OpenBSD (quad-core Intel
> i7-8650U processor; hyperthreading is disabled both in the BIOS and by
> default in OpenBSD). Of those 5 processes, 3 are at 'nice 20', and the
> other 2 are at 'nice 10'. I expected the 2 'nice 10' processes to each
> get more CPU time than the 3 'nice 20' processes, but 'top -S -i -s1'
> shows exactly the opposite behavior: the 3 'nice 20' processes are each
> getting MORE CPU time (about 100% of a CPU each) than the 2 'nice 1
> ' processes (about 50% of a CPU each):
>
> load averages: 5.04, 4.99, 4.04 gold.bkis-orchard.net
> 18:02:38
> 176 processes: 4 running, 168 idle, 4 on processor up 7 days,
> 17:40
> CPU0: 0.0% user, 97.0% nice, 0.0% sys, 0.0% spin, 3.0% intr, 0.0% idle
> CPU1: 1.0% user, 99.0% nice, 0.0% sys, 0.0% spin, 0.0% intr, 0.0% idle
> CPU2: 0.0% user, 100% nice, 0.0% sys, 0.0% spin, 0.0% intr, 0.0% idle
> CPU3: 1.0% user, 99.0% nice, 0.0% sys, 0.0% spin, 0.0% intr, 0.0% idle
> Memory: Real: 5686M/13G act/tot Free: 1929M Cache: 6785M Swap: 0K/34G
>
> PID USERNAME PRI NICE SIZE RES STATE WAIT TIME CPU COMMAND
> 95910 jonathan 104 20 39M 42M onproc/3 - 17:38 99.02% smp-O3
> 58006 jonathan 104 20 39M 42M run/2 - 42:45 98.97% smp-O3
> 63085 jonathan 104 20 39M 42M run/1 - 12:39 97.66% smp-O3
> 36985 jonathan 84 10 21M 24M onproc/0 - 5:57 49.66% smp-O3
> 95125 jonathan 84 10 21M 24M run/0 - 11:53 49.32% smp-O3
> 64031 _firefox 28 0 959M 1057M run/2 - 63:28 0.83%
> firefox-esr
> 77428 _firefox 2 0 1381M 1355M sleep/2 poll 179:14 0.10%
> firefox-esr
>
> Am I missing something obvious?
>
> --
> -- "Jonathan Thornburg [remove color- to reply]" <jthorn4...@pink-gmail.com>
> on the west coast of Canada, eh?
> "There was of course no way of knowing whether you were being watched
> at any given moment. How often, or on what system, the Thought Police
> plugged in on any individual wire was guesswork. It was even conceivable
> that they watched everybody all the time." -- George Orwell, "1984"
>
Are youre processes multithreaded?? Check with top -H.
-Otto
