From: Peter Zijlstra <peterz@infradead.org>
To: mingo@kernel.org, linux-kernel@vger.kernel.org, tj@kernel.org,
josef@toxicpanda.com
Cc: torvalds@linux-foundation.org, vincent.guittot@linaro.org,
efault@gmx.de, pjt@google.com, clm@fb.com,
dietmar.eggemann@arm.com, morten.rasmussen@arm.com,
bsegall@google.com, yuyang.du@intel.com, peterz@infradead.org
Subject: [PATCH -v2 03/18] sched/fair: Cure calc_cfs_shares() vs reweight_entity()
Date: Fri, 01 Sep 2017 15:21:02 +0200 [thread overview]
Message-ID: <20170901132748.141477819@infradead.org> (raw)
In-Reply-To: 20170901132059.342024223@infradead.org
[-- Attachment #1: peterz-sched-fair-calc_cfs_shares-fixup.patch --]
[-- Type: text/plain, Size: 1297 bytes --]
Vincent reported that when running in a cgroup, his root
cfs_rq->avg.load_avg dropped to 0 on task idle.
This is because reweight_entity() will now immediately propagate the
weight change of the group entity to its cfs_rq, and as it happens,
our approxmation (5) for calc_cfs_shares() results in 0 when the group
is idle.
Avoid this by using the correct (3) as a lower bound on (5). This way
the empty cgroup will slowly decay instead of instantly drop to 0.
Reported-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
kernel/sched/fair.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2703,11 +2703,10 @@ static long calc_cfs_shares(struct cfs_r
tg_shares = READ_ONCE(tg->shares);
/*
- * This really should be: cfs_rq->avg.load_avg, but instead we use
- * cfs_rq->load.weight, which is its upper bound. This helps ramp up
- * the shares for small weight interactive tasks.
+ * Because (5) drops to 0 when the cfs_rq is idle, we need to use (3)
+ * as a lower bound.
*/
- load = scale_load_down(cfs_rq->load.weight);
+ load = max(scale_load_down(cfs_rq->load.weight), cfs_rq->avg.load_avg);
tg_weight = atomic_long_read(&tg->load_avg);
next prev parent reply other threads:[~2017-09-01 13:37 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-09-01 13:20 [PATCH -v2 00/18] sched/fair: A bit of a cgroup/PELT overhaul Peter Zijlstra
2017-09-01 13:21 ` [PATCH -v2 01/18] sched/fair: Clean up calc_cfs_shares() Peter Zijlstra
2017-09-01 13:21 ` [PATCH -v2 02/18] sched/fair: Add comment to calc_cfs_shares() Peter Zijlstra
2017-09-28 10:03 ` Morten Rasmussen
2017-09-29 11:35 ` Peter Zijlstra
2017-09-29 13:03 ` Morten Rasmussen
2017-09-01 13:21 ` Peter Zijlstra [this message]
2017-09-29 9:04 ` [PATCH -v2 03/18] sched/fair: Cure calc_cfs_shares() vs reweight_entity() Morten Rasmussen
2017-09-29 11:38 ` Peter Zijlstra
2017-09-29 13:00 ` Morten Rasmussen
2017-09-01 13:21 ` [PATCH -v2 04/18] sched/fair: Remove se->load.weight from se->avg.load_sum Peter Zijlstra
2017-09-29 15:26 ` Morten Rasmussen
2017-09-29 16:39 ` Peter Zijlstra
2017-09-01 13:21 ` [PATCH -v2 05/18] sched/fair: Change update_load_avg() arguments Peter Zijlstra
2017-09-01 13:21 ` [PATCH -v2 06/18] sched/fair: Move enqueue migrate handling Peter Zijlstra
2017-09-01 13:21 ` [PATCH -v2 07/18] sched/fair: Rename {en,de}queue_entity_load_avg() Peter Zijlstra
2017-09-01 13:21 ` [PATCH -v2 08/18] sched/fair: Introduce {en,de}queue_load_avg() Peter Zijlstra
2017-09-01 13:21 ` [PATCH -v2 09/18] sched/fair: More accurate reweight_entity() Peter Zijlstra
2017-09-01 13:21 ` [PATCH -v2 10/18] sched/fair: Use reweight_entity() for set_user_nice() Peter Zijlstra
2017-09-01 13:21 ` [PATCH -v2 11/18] sched/fair: Rewrite cfs_rq->removed_*avg Peter Zijlstra
2017-09-01 13:21 ` [PATCH -v2 12/18] sched/fair: Rewrite PELT migration propagation Peter Zijlstra
2017-10-09 8:08 ` Morten Rasmussen
2017-10-09 9:45 ` Peter Zijlstra
2017-10-18 12:45 ` Morten Rasmussen
2017-10-30 13:35 ` Peter Zijlstra
2017-10-09 15:03 ` Vincent Guittot
2017-10-09 15:29 ` Vincent Guittot
2017-10-10 7:29 ` Peter Zijlstra
2017-10-10 7:44 ` Vincent Guittot
2017-10-13 15:22 ` Vincent Guittot
2017-10-13 20:41 ` Peter Zijlstra
2017-10-15 12:01 ` Vincent Guittot
2017-10-16 13:55 ` Vincent Guittot
2017-10-19 15:04 ` Vincent Guittot
2017-10-30 17:20 ` Peter Zijlstra
2017-10-31 11:14 ` Vincent Guittot
2017-10-31 15:01 ` Peter Zijlstra
2017-10-31 16:38 ` Vincent Guittot
2017-11-16 14:09 ` [PATCH v3] sched: Update runnable propagation rule Vincent Guittot
2017-11-16 14:21 ` [PATCH v4] " Vincent Guittot
2017-12-06 11:40 ` Peter Zijlstra
2017-12-06 17:10 ` Ingo Molnar
2017-12-06 20:29 ` [tip:sched/core] sched/fair: Update and fix the " tip-bot for Vincent Guittot
2017-09-01 13:21 ` [PATCH -v2 13/18] sched/fair: Propagate an effective runnable_load_avg Peter Zijlstra
2017-10-02 17:46 ` Dietmar Eggemann
2017-10-03 8:50 ` Peter Zijlstra
2017-10-03 9:29 ` Dietmar Eggemann
2017-10-03 12:26 ` Dietmar Eggemann
2017-09-01 13:21 ` [PATCH -v2 14/18] sched/fair: Synchonous PELT detach on load-balance migrate Peter Zijlstra
2017-09-01 13:21 ` [PATCH -v2 15/18] sched/fair: Align PELT windows between cfs_rq and its se Peter Zijlstra
2017-10-04 19:27 ` Dietmar Eggemann
2017-10-06 13:02 ` Peter Zijlstra
2017-10-09 12:15 ` Dietmar Eggemann
2017-10-09 12:19 ` Peter Zijlstra
2017-09-01 13:21 ` [PATCH -v2 16/18] sched/fair: More accurate async detach Peter Zijlstra
2017-09-01 13:21 ` [PATCH -v2 17/18] sched/fair: Calculate runnable_weight slightly differently Peter Zijlstra
2017-09-01 13:21 ` [PATCH -v2 18/18] sched/fair: Update calc_group_*() comments Peter Zijlstra
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