linux-kernel - [PATCH v3 00/10] sched/fair: task load tracking optimization and cleanup

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Message-Id: <20220801042745.7794-1-zhouchengming@bytedance.com>
Date:   Mon,  1 Aug 2022 12:27:35 +0800
From:   Chengming Zhou <zhouchengming@...edance.com>
To:     mingo@...hat.com, peterz@...radead.org, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        vschneid@...hat.com
Cc:     linux-kernel@...r.kernel.org,
        Chengming Zhou <zhouchengming@...edance.com>
Subject: [PATCH v3 00/10] sched/fair: task load tracking optimization and cleanup

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 and attach)
3. task switched_from/to_fair (detach later attach)

patch 01-03 cleanup the task change cgroup case by remove cpu_cgrp_subsys->fork(),
since we already do the same thing in sched_cgroup_fork().

patch 05 optimize the task migrate CPU case by combine detach into dequeue.

patch 06 fix another detach on unattached task case which has been woken up
by try_to_wake_up() but is waiting for actually being woken up by
sched_ttwu_pending().

patch 07 remove unnecessary limitation that we would fail when change
cgroup of forked task which hasn't been woken up by wake_up_new_task().

patch 08 refactor detach/attach_entity_cfs_rq by using update_load_avg()
DO_DETACH and DO_ATTACH flags.

patch 09-10 optimize post_init_entity_util_avg() for fair task and skip
setting util_avg and runnable_avg for !fair task.

Thanks!

Changes in v3:
 - One big change is this series don't freeze PELT sum/avg values to be
   used as initial values when re-entering fair any more, since these
   PELT values become much less relevant.
 - Reorder patches and collect tags from Vincent and Dietmar. Thanks!
 - Fix detach on unattached task which has been woken up by try_to_wake_up()
   but is waiting for actually being woken up by sched_ttwu_pending().
 - Delete TASK_NEW which limit forked task from changing cgroup.
 - Don't init util_avg and runnable_avg for !fair taks at fork time.

Changes in v2:
 - split task se depth maintenance into a separate patch3, suggested
   by Peter.
 - reorder patch6-7 before patch8-9, since we need update_load_avg()
   to do conditional attach/detach to avoid corner cases like twice
   attach problem.

Chengming Zhou (10):
  sched/fair: maintain task se depth in set_task_rq()
  sched/fair: remove redundant cpu_cgrp_subsys->fork()
  sched/fair: reset sched_avg last_update_time before set_task_rq()
  sched/fair: update comments in enqueue/dequeue_entity()
  sched/fair: combine detach into dequeue when migrating task
  sched/fair: fix another detach on unattached task corner case
  sched/fair: allow changing cgroup of new forked task
  sched/fair: refactor detach/attach_entity_cfs_rq using
    update_load_avg()
  sched/fair: defer task sched_avg attach to enqueue_entity()
  sched/fair: don't init util/runnable_avg for !fair task

 include/linux/sched.h |   5 +-
 kernel/sched/core.c   |  57 ++--------
 kernel/sched/fair.c   | 242 ++++++++++++++++++------------------------
 kernel/sched/sched.h  |   6 +-
 4 files changed, 119 insertions(+), 191 deletions(-)

-- 
2.36.1