linux-kernel - [PATCH 3.16 183/204] sched/topology: Optimize build_group

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Date:   Thu, 28 Dec 2017 17:05:44 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, riel@...hat.com,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        "Lauro Ramos Venancio" <lvenanci@...hat.com>, lwang@...hat.com,
        "Mike Galbraith" <efault@....de>, "Ingo Molnar" <mingo@...nel.org>,
        "Thomas Gleixner" <tglx@...utronix.de>,
        "Linus Torvalds" <torvalds@...ux-foundation.org>
Subject: [PATCH 3.16 183/204] sched/topology: Optimize build_group_mask()

3.16.52-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Lauro Ramos Venancio <lvenanci@...hat.com>

commit f32d782e31bf079f600dcec126ed117b0577e85c upstream.

The group mask is always used in intersection with the group CPUs. So,
when building the group mask, we don't have to care about CPUs that are
not part of the group.

Signed-off-by: Lauro Ramos Venancio <lvenanci@...hat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mike Galbraith <efault@....de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: lwang@...hat.com
Cc: riel@...hat.com
Link: http://lkml.kernel.org/r/1492717903-5195-2-git-send-email-lvenanci@redhat.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
[bwh: Backported to 3.16:
 - Update another reference to 'span' introduced by an earlier backport of
   sched/topology changes
 - Adjust filename]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 kernel/sched/core.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5782,14 +5782,14 @@ enum s_alloc {
 static void
 build_group_mask(struct sched_domain *sd, struct sched_group *sg, struct cpumask *mask)
 {
-	const struct cpumask *span = sched_domain_span(sd);
+	const struct cpumask *sg_span = sched_group_cpus(sg);
 	struct sd_data *sdd = sd->private;
 	struct sched_domain *sibling;
 	int i;
 
 	cpumask_clear(mask);
 
-	for_each_cpu(i, span) {
+	for_each_cpu(i, sg_span) {
 		sibling = *per_cpu_ptr(sdd->sd, i);
 
 		/*
@@ -5801,7 +5801,7 @@ build_group_mask(struct sched_domain *sd
 			continue;
 
 		/* If we would not end up here, we can't continue from here */
-		if (!cpumask_equal(span, sched_domain_span(sibling->child)))
+		if (!cpumask_equal(sg_span, sched_domain_span(sibling->child)))
 			continue;
 
 		cpumask_set_cpu(i, mask);