Messages in this thread | | | Date | Sun, 13 Mar 2022 13:37:37 +0800 | Subject | Re: [External] Re: Subject: [PATCH] sched/fair: prioritize normal task over sched_idle task with vruntime offset | From | chenying <> |
| |
在 2022/3/12 20:03, Peter Zijlstra 写道: > 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?
When colocating CPU-intensive jobs with latency-sensitive services can improve CPU utilization but it is difficult to meet the stringent tail-latency requirements of latency-sensitive services. We use a true idle time scheduler for CPU-intensive jobs to minimize the impact on latency-sensitive services.
| |