From b5454ecc76bb3122d801ad0ee762cc5e80544629 Mon Sep 17 00:00:00 2001
From: Peter Zijlstra <peterz@infradead.org>
Date: Fri, 12 May 2017 14:18:10 +0200
Subject: [PATCH] sched/fair: Implement more accurate async detach
References: bnc#1066110 Scheduler utilisation tracking
Patch-mainline: v4.15-rc1
Git-commit: 9a2dd585b2c431ec1e5d46a9d9568291c7a534cc
The problem with the overestimate is that it will subtract too big a
value from the load_sum, thereby pushing it down further than it ought
to go. Since runnable_load_avg is not subject to a similar 'force',
this results in the occasional 'runnable_load > load' situation.
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
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>
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
kernel/sched/fair.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 011c092596f8..d06f05b4b5e6 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3585,6 +3585,7 @@ update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
if (cfs_rq->removed.nr) {
unsigned long r;
+ u32 divider = LOAD_AVG_MAX - 1024 + sa->period_contrib;
raw_spin_lock(&cfs_rq->removed.lock);
swap(cfs_rq->removed.util_avg, removed_util);
@@ -3593,17 +3594,13 @@ update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
cfs_rq->removed.nr = 0;
raw_spin_unlock(&cfs_rq->removed.lock);
- /*
- * The LOAD_AVG_MAX for _sum is a slight over-estimate,
- * which is safe due to sub_positive() clipping at 0.
- */
r = removed_load;
sub_positive(&sa->load_avg, r);
- sub_positive(&sa->load_sum, r * LOAD_AVG_MAX);
+ sub_positive(&sa->load_sum, r * divider);
r = removed_util;
sub_positive(&sa->util_avg, r);
- sub_positive(&sa->util_sum, r * LOAD_AVG_MAX);
+ sub_positive(&sa->util_sum, r * divider);
add_tg_cfs_propagate(cfs_rq, -(long)removed_runnable_sum);