From: Barry Song <21cnbao@gmail.com>
To: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com,
vincent.guittot@linaro.org, rostedt@goodmis.org,
linux-kernel@vger.kernel.org
Cc: dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de,
bristot@redhat.com, Barry Song <song.bao.hua@hisilicon.com>
Subject: [PATCH] sched/fair: Remove the cost of a redundant cpumask_next_wrap in select_idle_cpu
Date: Tue, 23 Nov 2021 19:22:29 +0800 [thread overview]
Message-ID: <20211123112229.7812-1-21cnbao@gmail.com> (raw)
From: Barry Song <song.bao.hua@hisilicon.com>
This patch keeps the same scanning amount, but drops a redundant loop
of cpumask_next_wrap.
The original code did for_each_cpu_wrap(cpu, cpus, target + 1), then
checked --nr; this patch does --nr before doing the next loop, thus,
it can remove a cpumask_next_wrap() which costs a little bit.
Signed-off-by: Barry Song <song.bao.hua@hisilicon.com>
---
kernel/sched/fair.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index ff69f24..e2fb3e0 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6298,9 +6298,9 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool
span_avg = sd->span_weight * avg_idle;
if (span_avg > 4*avg_cost)
- nr = div_u64(span_avg, avg_cost);
+ nr = div_u64(span_avg, avg_cost) - 1;
else
- nr = 4;
+ nr = 3;
time = cpu_clock(this);
}
@@ -6312,11 +6312,11 @@ static int select_idle_cpu(struct task_struct *p, struct sched_domain *sd, bool
return i;
} else {
- if (!--nr)
- return -1;
idle_cpu = __select_idle_cpu(cpu, p);
if ((unsigned int)idle_cpu < nr_cpumask_bits)
break;
+ if (!--nr)
+ return -1;
}
}
--
1.8.3.1
next reply other threads:[~2021-11-23 11:22 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-23 11:22 Barry Song [this message]
2021-11-23 21:07 ` [PATCH] sched/fair: Remove the cost of a redundant cpumask_next_wrap in select_idle_cpu Peter Zijlstra
2021-11-24 0:07 ` Barry Song
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20211123112229.7812-1-21cnbao@gmail.com \
--to=21cnbao@gmail.com \
--cc=bristot@redhat.com \
--cc=bsegall@google.com \
--cc=dietmar.eggemann@arm.com \
--cc=juri.lelli@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=mgorman@suse.de \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=rostedt@goodmis.org \
--cc=song.bao.hua@hisilicon.com \
--cc=vincent.guittot@linaro.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.