From: Mel Gorman <mgorman@techsingularity.net>
To: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@kernel.org>
Cc: Vincent Guittot <vincent.guittot@linaro.org>,
Valentin Schneider <valentin.schneider@arm.com>,
Juri Lelli <juri.lelli@redhat.com>,
LKML <linux-kernel@vger.kernel.org>,
Mel Gorman <mgorman@techsingularity.net>
Subject: [PATCH 2/4] sched: Avoid unnecessary calculation of load imbalance at clone time
Date: Fri, 20 Nov 2020 09:06:28 +0000 [thread overview]
Message-ID: <20201120090630.3286-3-mgorman@techsingularity.net> (raw)
In-Reply-To: <20201120090630.3286-1-mgorman@techsingularity.net>
In find_idlest_group(), the load imbalance is only relevant when the group
is either overloaded or fully busy but it is calculated unconditionally.
This patch moves the imbalance calculation to the context it is required.
Technically, it is a micro-optimisation but really the benefit is avoiding
confusing one type of imbalance with another depending on the group_type
in the next patch.
No functional change.
Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
---
kernel/sched/fair.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 5fbed29e4001..9aded12aaa90 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8777,9 +8777,6 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
.group_type = group_overloaded,
};
- imbalance = scale_load_down(NICE_0_LOAD) *
- (sd->imbalance_pct-100) / 100;
-
do {
int local_group;
@@ -8833,6 +8830,11 @@ find_idlest_group(struct sched_domain *sd, struct task_struct *p, int this_cpu)
switch (local_sgs.group_type) {
case group_overloaded:
case group_fully_busy:
+
+ /* Calculate allowed imbalance based on load */
+ imbalance = scale_load_down(NICE_0_LOAD) *
+ (sd->imbalance_pct-100) / 100;
+
/*
* When comparing groups across NUMA domains, it's possible for
* the local domain to be very lightly loaded relative to the
--
2.26.2
next prev parent reply other threads:[~2020-11-20 9:06 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-20 9:06 [PATCH v3 0/4] Revisit NUMA imbalance tolerance and fork balancing Mel Gorman
2020-11-20 9:06 ` [PATCH 1/4] sched/numa: Rename nr_running and break out the magic number Mel Gorman
2020-11-20 13:32 ` Vincent Guittot
2020-11-25 14:02 ` [tip: sched/core] " tip-bot2 for Mel Gorman
2020-11-20 9:06 ` Mel Gorman [this message]
2020-11-20 13:32 ` [PATCH 2/4] sched: Avoid unnecessary calculation of load imbalance at clone time Vincent Guittot
2020-11-25 14:02 ` [tip: sched/core] " tip-bot2 for Mel Gorman
2020-11-20 9:06 ` [PATCH 3/4] sched/numa: Allow a floating imbalance between NUMA nodes Mel Gorman
2020-11-20 13:33 ` Vincent Guittot
2020-11-25 14:02 ` [tip: sched/core] " tip-bot2 for Mel Gorman
2020-11-20 9:06 ` [PATCH 4/4] sched: Limit the amount of NUMA imbalance that can exist at fork time Mel Gorman
2020-11-20 13:33 ` Vincent Guittot
2020-11-25 14:02 ` [tip: sched/core] " tip-bot2 for Mel Gorman
2020-11-20 12:58 ` [PATCH v3 0/4] Revisit NUMA imbalance tolerance and fork balancing Peter Zijlstra
2020-11-20 14:02 ` Mel Gorman
-- strict thread matches above, loose matches on Subject: below --
2020-11-19 8:30 [PATCH v2 " Mel Gorman
2020-11-19 8:30 ` [PATCH 2/4] sched: Avoid unnecessary calculation of load imbalance at clone time Mel Gorman
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