On 11/17/23 2:58 AM, Tobias Huschle Wrote:
#################### TRACE EXCERPT #################### The sched_place trace event was added to the end of the place_entity function and outputs: sev -> sched_entity vruntime sed -> sched_entity deadline sel -> sched_entity vlag avg -> cfs_rq avg_vruntime min -> cfs_rq min_vruntime cpu -> cpu of cfs_rq nr -> cfs_rq nr_running --- CPU 3/KVM-2950 [014] d.... 576.161432: sched_migrate_task: comm=vhost-2920 pid=2941 prio=120 orig_cpu=15 dest_cpu=14 --> migrates task from cpu 15 to 14 CPU 3/KVM-2950 [014] d.... 576.161433: sched_place: comm=vhost-2920 pid=2941 sev=4242563284 sed=4245563284 sel=0 avg=4242563284 min=4242563284 cpu=14 nr=0 --> places vhost 2920 on CPU 14 with vruntime 4242563284 CPU 3/KVM-2950 [014] d.... 576.161433: sched_place: comm= pid=0 sev=16329848593 sed=16334604010 sel=0 avg=16329848593 min=16329848593 cpu=14 nr=0 CPU 3/KVM-2950 [014] d.... 576.161433: sched_place: comm= pid=0 sev=42560661157 sed=42627443765 sel=0 avg=42560661157 min=42560661157 cpu=14 nr=0 CPU 3/KVM-2950 [014] d.... 576.161434: sched_place: comm= pid=0 sev=53846627372 sed=54125900099 sel=0 avg=53846627372 min=53846627372 cpu=14 nr=0 CPU 3/KVM-2950 [014] d.... 576.161434: sched_place: comm= pid=0 sev=86640641980 sed=87255041979 sel=0 avg=86640641980 min=86640641980 cpu=14 nr=0
As the following 2 lines indicates that vhost-2920 is on_rq so can be picked as next, thus its cfs_rq must have at least one entity. While the above 4 lines shows nr=0, so the "comm= pid=0" task(s) can't be in the same cgroup with vhost-2920. Say vhost is in cgroupA, and "comm= pid=0" task with sev=86640641980 is in cgroupB ...
CPU 3/KVM-2950 [014] dN... 576.161434: sched_stat_wait: comm=vhost-2920 pid=2941 delay=9958 [ns] CPU 3/KVM-2950 [014] d.... 576.161435: sched_switch: prev_comm=CPU 3/KVM prev_pid=2950 prev_prio=120 prev_state=S ==> next_comm=vhost-2920 next_pid=2941 next_prio=120 vhost-2920-2941 [014] D.... 576.161439: sched_waking: comm=vhost-2286 pid=2309 prio=120 target_cpu=008 vhost-2920-2941 [014] d.... 576.161446: sched_waking: comm=kworker/14:0 pid=6525 prio=120 target_cpu=014 vhost-2920-2941 [014] d.... 576.161447: sched_place: comm=kworker/14:0 pid=6525 sev=86642125805 sed=86645125805 sel=0 avg=86642125805 min=86642125805 cpu=14 nr=1 --> places kworker 6525 on cpu 14 with vruntime 86642125805 --> which is far larger than vhost vruntime of 4242563284
Here nr=1 means there is another entity in the same cfs_rq with the newly woken kworker, but which? According to the vruntime, I would assume kworker is in cgroupB.
