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From: Qi Zheng <arch0.zheng@gmail.com>
To: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
	vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
	rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de
Cc: linux-kernel@vger.kernel.org, Qi Zheng <arch0.zheng@gmail.com>
Subject: [PATCH] sched/core: add unlikely in group_has_capacity()
Date: Thu, 30 Jul 2020 21:54:23 +0800	[thread overview]
Message-ID: <20200730135423.232776-1-arch0.zheng@gmail.com> (raw)

1. The group_has_capacity() function is only called in
   group_classify().
2. Before calling the group_has_capacity() function,
   group_is_overloaded() will first judge the following
   formula, if it holds, the group_classify() will directly
   return the group_overloaded.

	(sgs->group_capacity * imbalance_pct) <
                        (sgs->group_runnable * 100)

Therefore, when the group_has_capacity() is called, the
probability that the above formalu holds is very small. Hint
compilers about that.

Signed-off-by: Qi Zheng <arch0.zheng@gmail.com>
---
 kernel/sched/fair.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 2ba8f230feb9..9074fd5e23b2 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -8234,8 +8234,8 @@ group_has_capacity(unsigned int imbalance_pct, struct sg_lb_stats *sgs)
 	if (sgs->sum_nr_running < sgs->group_weight)
 		return true;
 
-	if ((sgs->group_capacity * imbalance_pct) <
-			(sgs->group_runnable * 100))
+	if (unlikely((sgs->group_capacity * imbalance_pct) <
+			(sgs->group_runnable * 100)))
 		return false;
 
 	if ((sgs->group_capacity * 100) >
-- 
2.25.1


             reply	other threads:[~2020-07-30 13:54 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-30 13:54 Qi Zheng [this message]
2020-08-06 14:45 ` [PATCH] sched/core: add unlikely in group_has_capacity() Ingo Molnar
2020-08-07  2:47   ` Qi Zheng
2020-08-12  1:49     ` Qi Zheng
2020-08-17  8:18       ` Vincent Guittot

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