diff options
| author | Dietmar Eggemann <dietmar.eggemann@arm.com> | 2017-01-11 11:29:47 +0000 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2017-01-14 11:30:02 +0100 |
| commit | b8fd8423697b9ec729c5bb91737faad84ae19985 (patch) | |
| tree | 9bd269e627d0d1d197a8ea56c536641c5b3e9f36 /kernel/sched/fair.c | |
| parent | 89ee048f3cc796db6f26906c6bef4edf0bee70fd (diff) | |
sched/fair: Explain why MIN_SHARES isn't scaled in calc_cfs_shares()
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Peter 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: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/sched/fair.c')
| -rw-r--r-- | kernel/sched/fair.c | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 2b866a279bdf..274c747a01ce 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -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) |