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sched/fair: Improve PELT stuff some more
Vincent noted that the update_tg_load_avg() usage in commit:
3d30544f02
("sched/fair: Apply more PELT fixes")
isn't entirely sufficient. We need to call this function every time
cfs_rq->avg.load changes, this includes when update_cfs_rq_load_avg()
returns true, but {attach,detach}_entity_load_avg() themselves also
change it. This means we need to unconditionally call
update_tg_load_avg().
Also, add more comments.
Reported-by: Vincent Guittot <vincent.guittot@linaro.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
parent
a1fd46565b
commit
7c3edd2c30
1 changed files with 25 additions and 19 deletions
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@ -726,7 +726,6 @@ void post_init_entity_util_avg(struct sched_entity *se)
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struct sched_avg *sa = &se->avg;
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long cap = (long)(SCHED_CAPACITY_SCALE - cfs_rq->avg.util_avg) / 2;
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u64 now = cfs_rq_clock_task(cfs_rq);
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int tg_update;
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if (cap > 0) {
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if (cfs_rq->avg.util_avg != 0) {
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@ -759,10 +758,9 @@ void post_init_entity_util_avg(struct sched_entity *se)
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}
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}
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tg_update = update_cfs_rq_load_avg(now, cfs_rq, false);
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update_cfs_rq_load_avg(now, cfs_rq, false);
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attach_entity_load_avg(cfs_rq, se);
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if (tg_update)
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update_tg_load_avg(cfs_rq, false);
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update_tg_load_avg(cfs_rq, false);
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}
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#else /* !CONFIG_SMP */
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@ -2803,9 +2801,21 @@ __update_load_avg(u64 now, int cpu, struct sched_avg *sa,
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}
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#ifdef CONFIG_FAIR_GROUP_SCHED
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/*
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* Updating tg's load_avg is necessary before update_cfs_share (which is done)
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* and effective_load (which is not done because it is too costly).
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/**
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* update_tg_load_avg - update the tg's load avg
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* @cfs_rq: the cfs_rq whose avg changed
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* @force: update regardless of how small the difference
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*
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* This function 'ensures': tg->load_avg := \Sum tg->cfs_rq[]->avg.load.
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* However, because tg->load_avg is a global value there are performance
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* considerations.
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*
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* In order to avoid having to look at the other cfs_rq's, we use a
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* differential update where we store the last value we propagated. This in
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* turn allows skipping updates if the differential is 'small'.
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*
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* Updating tg's load_avg is necessary before update_cfs_share() (which is
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* done) and effective_load() (which is not done because it is too costly).
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*/
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static inline void update_tg_load_avg(struct cfs_rq *cfs_rq, int force)
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{
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@ -2931,10 +2941,10 @@ static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq)
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*
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* cfs_rq->avg is used for task_h_load() and update_cfs_share() for example.
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*
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* Returns true if the load decayed or we removed utilization. It is expected
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* that one calls update_tg_load_avg() on this condition, but after you've
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* modified the cfs_rq avg (attach/detach), such that we propagate the new
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* avg up.
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* Returns true if the load decayed or we removed load.
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*
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* Since both these conditions indicate a changed cfs_rq->avg.load we should
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* call update_tg_load_avg() when this function returns true.
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*/
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static inline int
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update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq, bool update_freq)
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@ -8442,7 +8452,6 @@ static void detach_task_cfs_rq(struct task_struct *p)
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struct sched_entity *se = &p->se;
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struct cfs_rq *cfs_rq = cfs_rq_of(se);
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u64 now = cfs_rq_clock_task(cfs_rq);
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int tg_update;
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if (!vruntime_normalized(p)) {
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/*
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@ -8454,10 +8463,9 @@ static void detach_task_cfs_rq(struct task_struct *p)
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}
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/* Catch up with the cfs_rq and remove our load when we leave */
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tg_update = update_cfs_rq_load_avg(now, cfs_rq, false);
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update_cfs_rq_load_avg(now, cfs_rq, false);
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detach_entity_load_avg(cfs_rq, se);
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if (tg_update)
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update_tg_load_avg(cfs_rq, false);
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update_tg_load_avg(cfs_rq, false);
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}
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static void attach_task_cfs_rq(struct task_struct *p)
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@ -8465,7 +8473,6 @@ static void attach_task_cfs_rq(struct task_struct *p)
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struct sched_entity *se = &p->se;
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struct cfs_rq *cfs_rq = cfs_rq_of(se);
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u64 now = cfs_rq_clock_task(cfs_rq);
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int tg_update;
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#ifdef CONFIG_FAIR_GROUP_SCHED
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/*
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@ -8476,10 +8483,9 @@ static void attach_task_cfs_rq(struct task_struct *p)
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#endif
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/* Synchronize task with its cfs_rq */
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tg_update = update_cfs_rq_load_avg(now, cfs_rq, false);
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update_cfs_rq_load_avg(now, cfs_rq, false);
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attach_entity_load_avg(cfs_rq, se);
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if (tg_update)
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update_tg_load_avg(cfs_rq, false);
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update_tg_load_avg(cfs_rq, false);
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if (!vruntime_normalized(p))
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se->vruntime += cfs_rq->min_vruntime;
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