linux-kernel - [PATCH v4 0/5] sync a se with its cfs

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Date:	Thu, 20 Aug 2015 20:21:55 +0900
From:	byungchul.park@....com
To:	mingo@...nel.org, peterz@...radead.org
Cc:	linux-kernel@...r.kernel.org, yuyang.du@...el.com,
	Byungchul Park <byungchul.park@....com>
Subject: [PATCH v4 0/5] sync a se with its cfs_rq when att(det)aching it

From: Byungchul Park <byungchul.park@....com>

there are 3 problems when att(det)aching a se to(from) its cfs_rq.

problem 1. se's average load is not accounted with new cfs_rq in queued case,
when a task changes its cgroup.

problem 2. cfs_rq->avg.load_avg becomes larger and larger whenever changing
cgroup to another. we have to sync se's average load with prev cfs_rq.

problem 3. current code does not sync it with its cfs_rq when switching
sched class to fair class. if we can always assume that a se has been
detached from fair class for a long time enough for its average load to
become useless, at the time attaching it to its fair class cfs_rq, then
current code is acceptable. but the assumption is not always true.

patch 1/5, does code refactoring for further patches.
patch 2/5, solves the problem 1.
patch 3/5, solves the problem 2.
patch 4/5, solves the problem 3.
patch 5/5, does code refactoring for better readability.

change from v3 to v4
* clean up code as Peter suggests
* use upper case letter in comment properly

change from v2 to v3 (logic is same as v2)
* fix up my poor english in commit message and comment
* break down big patches into more patches for being reviewed easily
* supplement cover letter messages

change from v1 to v2
* introduce two functions for adjusting vruntime and load when attaching
  and detaching.
* call the introduced functions instead of switched_from(to)_fair() directly
  in task_move_group_fair().
* add decaying logic for a se which has detached from a cfs_rq.

thanks,
byungchul

Byungchul Park (5):
  sched: add two functions adjusting cfs_rq's load when att(det)aching
    a se
  sched: make task_move_group_fair adjust cfs_rq's load in case of
    queued
  sched: sync a se with prev cfs_rq when changing cgroup
  sched: sync a se with its cfs_rq when switching sched class to fair
    class
  sched: add two functions for att(det)aching a task to(from) a cfs_rq

 kernel/sched/fair.c |  222 ++++++++++++++++++++++++++-------------------------
 1 file changed, 113 insertions(+), 109 deletions(-)

-- 
1.7.9.5

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