linux-kernel - [PATCH 0/7 v4] sched: reflect sched_entity move into task

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Date:   Mon, 26 Sep 2016 14:19:46 +0200
From:   Vincent Guittot <vincent.guittot@...aro.org>
To:     peterz@...radead.org, mingo@...nel.org,
        linux-kernel@...r.kernel.org, dietmar.eggemann@....com,
        kernellwp@...il.com
Cc:     yuyang.du@...el.com, Morten.Rasmussen@....com,
        linaro-kernel@...ts.linaro.org, pjt@...gle.com, bsegall@...gle.com,
        Vincent Guittot <vincent.guittot@...aro.org>
Subject: [PATCH 0/7 v4] sched: reflect sched_entity move into task_group's load

Ensure that the move of a sched_entity will be reflected in load and
utilization of the task_group hierarchy.

When a sched_entity moves between groups or CPUs, load and utilization
of cfs_rq don't reflect the changes immediately but converge to new values.
As a result, the metrics are no more aligned with the new balance of the
load in the system and next decisions will have a biased view.

This patchset synchronizes load/utilization of sched_entity with its child
cfs_rq (se->my-q) only when tasks move to/from child cfs_rq:
-move between task group
-migration between CPUs
Otherwise, PELT is updated as usual.

This version doesn't include any changes related to discussion that have
started during the review of the previous version about:
- encapsulate the sequence for changing the propoerty of a task
- remove a cfs_rq from list during update_blocked_averages  
These topics don't gain anything from being added in this patchset as they
are fairly independent and deserve a separate patch.

Changes since v3:
- Replaced the 2 arguments of update_load_avg by 1 flags argument
- Propagated move in runnable_load_avg when sched_entity is already on_rq
- Ensure that intermediate value will not reach memory when updating load and
  utilization
- Optimize the the calculation of load_avg of the sched_entity
- Fixed some typo

Changes since v2:
- Propagate both utilization and load
- Synced sched_entity and se->my_q instead of adding the delta

Changes since v1:
- This patch needs the patch that fixes issue with rq->leaf_cfs_rq_list
  "sched: fix hierarchical order in rq->leaf_cfs_rq_list" in order to work
  correctly. I haven't sent them as a single patchset because the fix is
  independent of this one
- Merge some functions that are always used together
- During update of blocked load, ensure that the sched_entity is synced
  with the cfs_rq applying changes
- Fix an issue when task changes its cpu affinity
Vincent Guittot (7):
  sched: factorize attach entity
  sched: fix hierarchical order in rq->leaf_cfs_rq_list
  sched: factorize PELT update
  sched: propagate load during synchronous attach/detach
  sched: propagate asynchrous detach
  sched: fix task group initialization
  sched: fix wrong utilization accounting when switching to fair class

 kernel/sched/core.c  |  21 +--
 kernel/sched/fair.c  | 354 +++++++++++++++++++++++++++++++++++++++++----------
 kernel/sched/sched.h |   2 +
 3 files changed, 300 insertions(+), 77 deletions(-)

-- 
1.9.1