linux-kernel - [PATCH RFC 5/5] sched/fair: remove impossible condition from find_idlest_group

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Date:   Sat, 28 Oct 2017 02:59:41 -0700
From:   Joel Fernandes <joelaf@...gle.com>
To:     linux-kernel@...r.kernel.org
Cc:     Joel Fernandes <joelaf@...gle.com>, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Brendan Jackman <brendan.jackman@....com>,
        Dietmar <dietmar.eggemann@....com>,
        "Cc: Srinivas Pandruvada" <srinivas.pandruvada@...ux.intel.com>,
        "Cc: Len Brown" <lenb@...nel.org>,
        "Cc: Rafael J. Wysocki" <rjw@...ysocki.net>,
        "Cc: Viresh Kumar" <viresh.kumar@...aro.org>,
        "Cc: Juri Lelli" <juri.lelli@....com>,
        "Cc: Patrick Bellasi" <patrick.bellasi@....com>,
        "Cc: Steve Muckle" <smuckle@...gle.com>,
        "Cc: Chris Redpath" <Chris.Redpath@....com>,
        "Cc: Atish Patra" <atish.patra@...cle.com>,
        "Cc: Vincent Guittot" <vincent.guittot@...aro.org>,
        "Cc: Morten Ramussen" <morten.rasmussen@....com>,
        "Cc: Frederic Weisbecker" <fweisbec@...il.com>,
        "Cc: Thomas Gleixner" <tglx@...utronix.de>,
        "Cc: EAS Dev" <eas-dev@...ts.linaro.org>,
        "Cc: Android Kernel" <kernel-team@...roid.com>
Subject: [PATCH RFC 5/5] sched/fair: remove impossible condition from find_idlest_group_cpu

find_idlest_group_cpu goes through CPUs of a group previous selected by
find_idlest_group. find_idlest_group returns NULL if the local group is the
selected one and doesn't execute find_idlest_group_cpu if the group to which
'cpu' belongs to is chosen. So we're always guaranteed to call
find_idlest_group_cpu with a group to which cpu is non-local. This makes one of
the conditions in find_idlest_group_cpu an impossible one, which we can get rid
off.

Cc: Ingo Molnar <mingo@...hat.com>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Brendan Jackman <brendan.jackman@....com>
Cc: Dietmar <dietmar.eggemann@....com>
Signed-off-by: Joel Fernandes <joelaf@...gle.com>
---
 kernel/sched/fair.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 5c49fdb4c508..740602ce799f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5922,7 +5922,7 @@ find_idlest_group_cpu(struct sched_group *group, struct task_struct *p, int this
 			}
 		} else if (shallowest_idle_cpu == -1) {
 			load = weighted_cpuload(cpu_rq(i));
-			if (load < min_load || (load == min_load && i == this_cpu)) {
+			if (load < min_load) {
 				min_load = load;
 				least_loaded_cpu = i;
 			}
-- 
2.15.0.rc2.357.g7e34df9404-goog