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| author | Vincent Guittot <vincent.guittot@linaro.org> | 2018-06-14 12:33:00 +0200 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2018-07-03 09:17:30 +0200 |
| commit | 3482d98bbc730758b63a5d1cf41d05ea17481412 (patch) | |
| tree | 40efeeb7f875d4424d3a070315656392f5a89768 /kernel | |
| parent | f1d1be8aee6c461652aea8f58bedebaa73d7f4d3 (diff) | |
| download | lwn-3482d98bbc730758b63a5d1cf41d05ea17481412.tar.gz lwn-3482d98bbc730758b63a5d1cf41d05ea17481412.zip | |
sched/util_est: Fix util_est_dequeue() for throttled cfs_rq
When a cfs_rq is throttled, parent cfs_rq->nr_running is decreased and
everything happens at cfs_rq level. Currently util_est stays unchanged
in such case and it keeps accounting the utilization of throttled tasks.
This can somewhat make sense as we don't dequeue tasks but only throttled
cfs_rq.
If a task of another group is enqueued/dequeued and root cfs_rq becomes
idle during the dequeue, util_est will be cleared whereas it was
accounting util_est of throttled tasks before. So the behavior of util_est
is not always the same regarding throttled tasks and depends of side
activity. Furthermore, util_est will not be updated when the cfs_rq is
unthrottled as everything happens at cfs_rq level. Main results is that
util_est will stay null whereas we now have running tasks. We have to wait
for the next dequeue/enqueue of the previously throttled tasks to get an
up to date util_est.
Remove the assumption that cfs_rq's estimated utilization of a CPU is 0
if there is no running task so the util_est of a task remains until the
latter is dequeued even if its cfs_rq has been throttled.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Patrick Bellasi <patrick.bellasi@arm.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Fixes: 7f65ea42eb00 ("sched/fair: Add util_est on top of PELT")
Link: http://lkml.kernel.org/r/1528972380-16268-1-git-send-email-vincent.guittot@linaro.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched/fair.c | 16 |
1 files changed, 4 insertions, 12 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 840b92ee6f89..2f0a0be4d344 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -3982,18 +3982,10 @@ util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep) if (!sched_feat(UTIL_EST)) return; - /* - * Update root cfs_rq's estimated utilization - * - * If *p is the last task then the root cfs_rq's estimated utilization - * of a CPU is 0 by definition. - */ - ue.enqueued = 0; - if (cfs_rq->nr_running) { - ue.enqueued = cfs_rq->avg.util_est.enqueued; - ue.enqueued -= min_t(unsigned int, ue.enqueued, - (_task_util_est(p) | UTIL_AVG_UNCHANGED)); - } + /* Update root cfs_rq's estimated utilization */ + ue.enqueued = cfs_rq->avg.util_est.enqueued; + ue.enqueued -= min_t(unsigned int, ue.enqueued, + (_task_util_est(p) | UTIL_AVG_UNCHANGED)); WRITE_ONCE(cfs_rq->avg.util_est.enqueued, ue.enqueued); /* |