sched/fair: Spread out tasks evenly when not overloaded
When there is only one CPU per group, using the idle CPUs to evenly spread tasks doesn't make sense and nr_running is a better metrics. Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org> Cc: Ben Segall <bsegall@google.com> Cc: Dietmar Eggemann <dietmar.eggemann@arm.com> Cc: Juri Lelli <juri.lelli@redhat.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Mike Galbraith <efault@gmx.de> Cc: Morten.Rasmussen@arm.com Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: hdanton@sina.com Cc: parth@linux.ibm.com Cc: pauld@redhat.com Cc: quentin.perret@arm.com Cc: riel@surriel.com Cc: srikar@linux.vnet.ibm.com Cc: valentin.schneider@arm.com Link: https://lkml.kernel.org/r/1571405198-27570-8-git-send-email-vincent.guittot@linaro.org Signed-off-by: Ingo Molnar <mingo@kernel.org>
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@ -8591,18 +8591,34 @@ static struct sched_group *find_busiest_group(struct lb_env *env)
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busiest->sum_nr_running > local->sum_nr_running + 1)
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goto force_balance;
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if (busiest->group_type != group_overloaded &&
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(env->idle == CPU_NOT_IDLE ||
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local->idle_cpus <= (busiest->idle_cpus + 1)))
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/*
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* If the busiest group is not overloaded
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* and there is no imbalance between this and busiest group
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* wrt. idle CPUs, it is balanced. The imbalance
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* becomes significant if the diff is greater than 1 otherwise
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* we might end up just moving the imbalance to another
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* group.
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*/
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goto out_balanced;
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if (busiest->group_type != group_overloaded) {
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if (env->idle == CPU_NOT_IDLE)
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/*
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* If the busiest group is not overloaded (and as a
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* result the local one too) but this CPU is already
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* busy, let another idle CPU try to pull task.
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*/
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goto out_balanced;
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if (busiest->group_weight > 1 &&
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local->idle_cpus <= (busiest->idle_cpus + 1))
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/*
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* If the busiest group is not overloaded
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* and there is no imbalance between this and busiest
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* group wrt idle CPUs, it is balanced. The imbalance
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* becomes significant if the diff is greater than 1
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* otherwise we might end up to just move the imbalance
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* on another group. Of course this applies only if
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* there is more than 1 CPU per group.
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*/
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goto out_balanced;
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if (busiest->sum_h_nr_running == 1)
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/*
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* busiest doesn't have any tasks waiting to run
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*/
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goto out_balanced;
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}
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force_balance:
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/* Looks like there is an imbalance. Compute it */
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