From: Brendan Jackman <brendan.jackman@arm.com>
To: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
linux-kernel@vger.kernel.org
Cc: Joel Fernandes <joelaf@google.com>,
Andres Oportus <andresoportus@google.com>,
Dietmar Eggemann <dietmar.eggemann@arm.com>,
Vincent Guittot <vincent.guittot@linaro.org>,
Josef Bacik <josef@toxicpanda.com>,
Morten Rasmussen <morten.rasmussen@arm.com>
Subject: [PATCH v2 4/5] sched/fair: Fix use of find_idlest_group when no groups are allowed
Date: Fri, 25 Aug 2017 11:16:31 +0100 [thread overview]
Message-ID: <20170825101632.28065-5-brendan.jackman@arm.com> (raw)
In-Reply-To: <20170825101632.28065-1-brendan.jackman@arm.com>
When p is allowed on none of the CPUs in the sched_domain, we
currently return NULL from find_idlest_group, and pointlessly
continue the search on lower sched_domain levels (where p is also not
allowed) before returning prev_cpu regardless (as we have not updated
new_cpu).
Add an explicit check for this case, and a comment to
find_idlest_group. Now when find_idlest_group returns NULL, it always
means that the local group is allowed and idlest.
Signed-off-by: Brendan Jackman <brendan.jackman@arm.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Josef Bacik <josef@toxicpanda.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Morten Rasmussen <morten.rasmussen@arm.com>
Cc: Peter Zijlstra <peterz@infradead.org>
---
kernel/sched/fair.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 0ce75bbcde45..26080917ff8d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -5380,6 +5380,8 @@ static unsigned long capacity_spare_wake(int cpu, struct task_struct *p)
/*
* find_idlest_group finds and returns the least busy CPU group within the
* domain.
+ *
+ * Assumes p is allowed on at least one CPU in sd.
*/
static struct sched_group *
find_idlest_group(struct sched_domain *sd, struct task_struct *p,
@@ -5567,6 +5569,9 @@ static inline int find_idlest_cpu(struct sched_domain *sd, struct task_struct *p
{
int new_cpu = prev_cpu;
+ if (!cpumask_intersects(sched_domain_span(sd), &p->cpus_allowed))
+ return prev_cpu;
+
while (sd) {
struct sched_group *group;
struct sched_domain *tmp;
--
2.14.1
next prev parent reply other threads:[~2017-08-25 10:17 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-25 10:16 [PATCH v2 0/5] sched/fair: Tweaks for select_task_rq_fair slowpath Brendan Jackman
2017-08-25 10:16 ` [PATCH v2 1/5] sched/fair: Move select_task_rq_fair slow-path into its own function Brendan Jackman
2017-08-25 12:22 ` Josef Bacik
2017-08-25 13:40 ` Vincent Guittot
2017-08-25 10:16 ` [PATCH v2 2/5] sched/fair: Remove unnecessary comparison with -1 Brendan Jackman
2017-08-25 12:44 ` Josef Bacik
2017-08-25 13:40 ` Vincent Guittot
2017-08-25 10:16 ` [PATCH v2 3/5] sched/fair: Fix find_idlest_group when local group is not allowed Brendan Jackman
2017-08-25 13:39 ` Vincent Guittot
2017-08-25 10:16 ` Brendan Jackman [this message]
2017-08-25 13:39 ` [PATCH v2 4/5] sched/fair: Fix use of find_idlest_group when no groups are allowed Vincent Guittot
2017-08-25 10:16 ` [PATCH v2 5/5] sched/fair: Fix use of find_idlest_group when local group is idlest Brendan Jackman
2017-08-25 13:38 ` Vincent Guittot
2017-08-25 15:51 ` Brendan Jackman
2017-08-28 8:56 ` Vincent Guittot
2017-08-28 9:11 ` Vincent Guittot
2017-08-29 17:09 ` Brendan Jackman
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