linux-kernel - [PATCH v2 2/3] sched/fair: util_est: mask UTIL_AVG

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Date:   Mon,  5 Nov 2018 14:53:59 +0000
From:   Patrick Bellasi <patrick.bellasi@....com>
To:     linux-kernel@...r.kernel.org
Cc:     Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Quentin Perret <quentin.perret@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Todd Kjos <tkjos@...gle.com>,
        Steve Muckle <smuckle@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Ingo Molnar <mingo@...nel.org>
Subject: [PATCH v2 2/3] sched/fair: util_est: mask UTIL_AVG_UNCHANGED usages

The _task_util_est() is mainly used to add/remove the task contribution
to/from the rq's estimated utilization at task enqueue/dequeue time.
In both cases we ensure the UTIL_AVG_UNCHANGED flag is set to keep
consistency between enqueue and dequeue time while still being
transparent to update_load_avg calls which will eventually reset the
flag.

Let's move the flag forcing within _task_util_est() itself so that we
can simplify calling code by hiding that estimated utilization
implementation detail into one of its internal functions.

This will affect also the "public" API task_util_est() but we know that
the flag will (eventually) impact just on the LSB of the estimated
utilization, thus it's certainly acceptable.

Signed-off-by: Patrick Bellasi <patrick.bellasi@....com>
Cc: Ingo Molnar <mingo@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: linux-kernel@...r.kernel.org
---
 kernel/sched/fair.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 473a9cc559e8..aeb37fe4dbb1 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3604,7 +3604,7 @@ static inline unsigned long _task_util_est(struct task_struct *p)
 {
 	struct util_est ue = READ_ONCE(p->se.avg.util_est);
 
-	return max(ue.ewma, ue.enqueued);
+	return (max(ue.ewma, ue.enqueued) | UTIL_AVG_UNCHANGED);
 }
 
 static inline unsigned long task_util_est(struct task_struct *p)
@@ -3622,7 +3622,7 @@ static inline void util_est_enqueue(struct cfs_rq *cfs_rq,
 
 	/* Update root cfs_rq's estimated utilization */
 	enqueued  = cfs_rq->avg.util_est.enqueued;
-	enqueued += (_task_util_est(p) | UTIL_AVG_UNCHANGED);
+	enqueued += _task_util_est(p);
 	WRITE_ONCE(cfs_rq->avg.util_est.enqueued, enqueued);
 }
 
@@ -3650,8 +3650,7 @@ util_est_dequeue(struct cfs_rq *cfs_rq, struct task_struct *p, bool task_sleep)
 
 	/* 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));
+	ue.enqueued -= min_t(unsigned int, ue.enqueued, _task_util_est(p));
 	WRITE_ONCE(cfs_rq->avg.util_est.enqueued, ue.enqueued);
 
 	/*
@@ -6292,7 +6291,7 @@ static unsigned long cpu_util_without(int cpu, struct task_struct *p)
 		 */
 		if (unlikely(task_on_rq_queued(p) || current == p)) {
 			estimated -= min_t(unsigned int, estimated,
-					   (_task_util_est(p) | UTIL_AVG_UNCHANGED));
+					   _task_util_est(p));
 		}
 		util = max(util, estimated);
 	}
-- 
2.18.0