summaryrefslogtreecommitdiff
path: root/kernel
diff options
context:
space:
mode:
authorVincent Guittot <vincent.guittot@linaro.org>2018-06-14 12:33:00 +0200
committerIngo Molnar <mingo@kernel.org>2018-07-03 09:17:30 +0200
commit3482d98bbc730758b63a5d1cf41d05ea17481412 (patch)
tree40efeeb7f875d4424d3a070315656392f5a89768 /kernel
parentf1d1be8aee6c461652aea8f58bedebaa73d7f4d3 (diff)
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.c16
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);
/*