Messages in this thread |  | | Date | Sat, 12 Mar 2022 13:03:09 +0100 | From | Peter Zijlstra <> | Subject | Re: Subject: [PATCH] sched/fair: prioritize normal task over sched_idle task with vruntime offset |
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On Fri, Mar 11, 2022 at 03:58:47PM +0800, chenying wrote: > We add a time offset to the se->vruntime when the idle sched_entity > is enqueued, so that the idle entity will always be on the right of > the non-idle in the runqueue. This can allow non-idle tasks to be > selected and run before the idle. > > A use-case is that sched_idle for background tasks and non-idle > for foreground. The foreground tasks are latency sensitive and do > not want to be disturbed by the background. It is well known that > the idle tasks can be preempted by the non-idle tasks when waking up, > but will not distinguish between idle and non-idle when pick the next > entity. This may cause background tasks to disturb the foreground. > > Test results as below: > > ~$ ./loop.sh & > [1] 764 > ~$ chrt -i 0 ./loop.sh & > [2] 765 > ~$ taskset -p 04 764 > ~$ taskset -p 04 765 > > ~$ top -p 764 -p 765 > top - 13:10:01 up 1 min, 2 users, load average: 1.30, 0.38, 0.13 > Tasks: 2 total, 2 running, 0 sleeping, 0 stopped, 0 zombie > %Cpu(s): 12.5 us, 0.0 sy, 0.0 ni, 87.4 id, 0.0 wa, 0.0 hi, 0.0 si, 0.0 > st > KiB Mem : 16393492 total, 16142256 free, 111028 used, 140208 buff/cache > KiB Swap: 385836 total, 385836 free, 0 used. 16037992 avail Mem > > PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND > 764 chenyin+ 20 0 12888 1144 1004 R 100.0 0.0 1:05.12 loop.sh > 765 chenyin+ 20 0 12888 1224 1080 R 0.0 0.0 0:16.21 loop.sh > > The non-idle process (764) can run at 100% and without being disturbed by > the idle process (765).
Did you just do a very complicated true idle time scheduler, with all the problems that brings?
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