Commit-ID: 4ad3831a9d4af5e36da5d44a3b9c6522d0353cee Gitweb: https://git.kernel.org/tip/4ad3831a9d4af5e36da5d44a3b9c6522d0353cee Author: Chris Redpath <chris.redp...@arm.com> AuthorDate: Wed, 4 Jul 2018 11:17:48 +0100 Committer: Ingo Molnar <mi...@kernel.org> CommitDate: Mon, 10 Sep 2018 11:05:53 +0200
sched/fair: Don't move tasks to lower capacity CPUs unless necessary When lower capacity CPUs are load balancing and considering to pull something from a higher capacity group, we should not pull tasks from a CPU with only one task running as this is guaranteed to impede progress for that task. If there is more than one task running, load balance in the higher capacity group would have already made any possible moves to resolve imbalance and we should make better use of system compute capacity by moving a task if we still have more than one running. Signed-off-by: Chris Redpath <chris.redp...@arm.com> Signed-off-by: Morten Rasmussen <morten.rasmus...@arm.com> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Peter Zijlstra <pet...@infradead.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: dietmar.eggem...@arm.com Cc: gaku.inami...@renesas.com Cc: valentin.schnei...@arm.com Cc: vincent.guit...@linaro.org Link: http://lkml.kernel.org/r/1530699470-29808-11-git-send-email-morten.rasmus...@arm.com Signed-off-by: Ingo Molnar <mi...@kernel.org> --- kernel/sched/fair.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 8b228c5b3eb4..06ff75f4ac7b 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -8423,6 +8423,17 @@ static struct rq *find_busiest_queue(struct lb_env *env, capacity = capacity_of(i); + /* + * For ASYM_CPUCAPACITY domains, don't pick a CPU that could + * eventually lead to active_balancing high->low capacity. + * Higher per-CPU capacity is considered better than balancing + * average load. + */ + if (env->sd->flags & SD_ASYM_CPUCAPACITY && + capacity_of(env->dst_cpu) < capacity && + rq->nr_running == 1) + continue; + wl = weighted_cpuload(rq); /*
