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Commit b8fd8423 authored by Dietmar Eggemann's avatar Dietmar Eggemann Committed by Ingo Molnar
Browse files

sched/fair: Explain why MIN_SHARES isn't scaled in calc_cfs_shares() 



Signed-off-by: default avatarDietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Turner <pjt@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Samuel Thibault <samuel.thibault@ens-lyon.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/e9a4d858-bcf3-36b9-e3a9-449953e34569@arm.com


Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
parent 89ee048f

kernel/sched/fair.c

+12 −0
Original line number Diff line number Diff line
@@ -2657,6 +2657,18 @@ static long calc_cfs_shares(struct cfs_rq *cfs_rq, struct task_group *tg) 
	if (tg_weight)

		shares /= tg_weight;



	/*

	 * MIN_SHARES has to be unscaled here to support per-CPU partitioning

	 * of a group with small tg->shares value. It is a floor value which is

	 * assigned as a minimum load.weight to the sched_entity representing

	 * the group on a CPU.

	 *

	 * E.g. on 64-bit for a group with tg->shares of scale_load(15)=15*1024

	 * on an 8-core system with 8 tasks each runnable on one CPU shares has

	 * to be 15*1024*1/8=1920 instead of scale_load(MIN_SHARES)=2*1024. In

	 * case no task is runnable on a CPU MIN_SHARES=2 should be returned

	 * instead of 0.

	 */

	if (shares < MIN_SHARES)

		shares = MIN_SHARES;

	if (shares > tg->shares)