[PATCH 0/8] sched: task load tracking optimization and cleanup

From: Chengming Zhou
Date: Sat Jul 09 2022 - 11:16:00 EST

Hi all,

This patch series is optimization and cleanup for task load tracking
when task migrate CPU/cgroup or switched_from/to_fair().

There are three types of detach/attach_entity_load_avg (except fork and
exit case) for a fair task:
1. task migrate CPU (on_rq migrate or wake_up migrate)
2. task migrate cgroup (detach then attach)
3. task switched_from/to_fair (detach later attach)

patch1 optimize the on_rq migrate CPU case by combine detach into dequeue,
so we don't need to do detach_entity_cfs_rq() in migrate_task_rq_fair()
any more.

patch3 cleanup the migrate cgroup case by remove cpu_cgrp_subsys->fork(),
since we already do the same thing in sched_cgroup_fork().

patch1-3 have been reviewed earlier, but conflicts with the current tip
tree, so include them here as a patchset. Sorry for the inconvenience.

patch5-6 fix load tracking for new forked !fair task and when task

After these changes, the task sched_avg last_update_time is reset to 0
when migrate from CPU/cgroup or switched_from_fair(), to save updated
sched_avg for next attach.

patch7-8 delete superfluous set_task_rq_fair() and SKIP_AGE_LOAD.

Chengming Zhou (8):
sched/fair: combine detach into dequeue when migrating task
sched/fair: update comments in enqueue/dequeue_entity()
sched/fair: remove redundant cpu_cgrp_subsys->fork()
sched/fair: reset sched_avg last_update_time before set_task_rq()
sched/fair: fix load tracking for new forked !fair task
sched/fair: stop load tracking when task switched_from_fair()
sched/fair: delete superfluous set_task_rq_fair()
sched/fair: delete superfluous SKIP_AGE_LOAD

kernel/sched/core.c | 27 ++------
kernel/sched/fair.c | 139 ++++++++++------------------------------
kernel/sched/features.h | 1 -
kernel/sched/sched.h | 14 +---
4 files changed, 41 insertions(+), 140 deletions(-)