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sched/pelt: Continue to relax the sync of util_sum with util_avg
Rick reported performance regressions in bugzilla because of cpu frequency
being lower than before:
https://bugzilla.kernel.org/show_bug.cgi?id=215045
He bisected the problem to:
commit 1c35b07e6d
("sched/fair: Ensure _sum and _avg values stay consistent")
This commit forces util_sum to be synced with the new util_avg after
removing the contribution of a task and before the next periodic sync. By
doing so util_sum is rounded to its lower bound and might lost up to
LOAD_AVG_MAX-1 of accumulated contribution which has not yet been
reflected in util_avg.
update_tg_cfs_util() is not the only place where we round util_sum and
lost some accumulated contributions that are not already reflected in
util_avg. Modify update_tg_cfs_util() and detach_entity_load_avg() to not
sync util_sum with the new util_avg. Instead of always setting util_sum to
the low bound of util_avg, which can significantly lower the utilization,
we propagate the difference. In addition, we also check that cfs's util_sum
always stays above the lower bound for a given util_avg as it has been
observed that sched_entity's util_sum is sometimes above cfs one.
Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Tested-by: Sachin Sant <sachinp@linux.ibm.com>
Link: https://lkml.kernel.org/r/20220111134659.24961-3-vincent.guittot@linaro.org
This commit is contained in:
parent
98b0d89022
commit
7ceb771030
1 changed files with 18 additions and 7 deletions
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@ -3451,11 +3451,11 @@ void set_task_rq_fair(struct sched_entity *se,
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static inline void
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update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq *gcfs_rq)
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{
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long delta = gcfs_rq->avg.util_avg - se->avg.util_avg;
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u32 divider;
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long delta_sum, delta_avg = gcfs_rq->avg.util_avg - se->avg.util_avg;
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u32 new_sum, divider;
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/* Nothing to update */
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if (!delta)
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if (!delta_avg)
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return;
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/*
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@ -3464,13 +3464,20 @@ update_tg_cfs_util(struct cfs_rq *cfs_rq, struct sched_entity *se, struct cfs_rq
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*/
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divider = get_pelt_divider(&cfs_rq->avg);
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/* Set new sched_entity's utilization */
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se->avg.util_avg = gcfs_rq->avg.util_avg;
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se->avg.util_sum = se->avg.util_avg * divider;
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new_sum = se->avg.util_avg * divider;
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delta_sum = (long)new_sum - (long)se->avg.util_sum;
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se->avg.util_sum = new_sum;
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/* Update parent cfs_rq utilization */
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add_positive(&cfs_rq->avg.util_avg, delta);
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cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * divider;
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add_positive(&cfs_rq->avg.util_avg, delta_avg);
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add_positive(&cfs_rq->avg.util_sum, delta_sum);
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/* See update_cfs_rq_load_avg() */
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cfs_rq->avg.util_sum = max_t(u32, cfs_rq->avg.util_sum,
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cfs_rq->avg.util_avg * PELT_MIN_DIVIDER);
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}
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static inline void
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@ -3790,7 +3797,11 @@ static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s
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dequeue_load_avg(cfs_rq, se);
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sub_positive(&cfs_rq->avg.util_avg, se->avg.util_avg);
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cfs_rq->avg.util_sum = cfs_rq->avg.util_avg * divider;
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sub_positive(&cfs_rq->avg.util_sum, se->avg.util_sum);
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/* See update_cfs_rq_load_avg() */
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cfs_rq->avg.util_sum = max_t(u32, cfs_rq->avg.util_sum,
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cfs_rq->avg.util_avg * PELT_MIN_DIVIDER);
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sub_positive(&cfs_rq->avg.runnable_avg, se->avg.runnable_avg);
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cfs_rq->avg.runnable_sum = cfs_rq->avg.runnable_avg * divider;
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