Commit 90f309fb authored Jan 26, 2015 by Dietmar Eggemann Committed by Dmitry Shmidt Jan 31, 2017

ANDROID: sched: Enable idle balance to pull single task towards cpu with higher capacity



We do not want to miss out on the ability to pull a single remaining
task from a potential source cpu towards an idle destination cpu. Add an
extra criteria to need_active_balance() to kick off active load balance
if the source cpu is over-utilized and has lower capacity than the
destination cpu.

cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Morten Rasmussen <morten.rasmussen@arm.com>
Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Signed-off-by: Andres Oportus <andresoportus@google.com>

parent de9b6366

kernel/sched/fair.c

+12 −0

Original line number	Diff line number	Diff line
		@@ -5235,6 +5235,11 @@ static inline bool task_fits_spare(struct task_struct *p, int cpu)
		return __task_fits(p, cpu, cpu_util(cpu));
		}

		static bool cpu_overutilized(int cpu)
		{
		return (capacity_of(cpu) * 1024) < (cpu_util(cpu) * capacity_margin);
		}

		/*
		* find_idlest_group finds and returns the least busy CPU group within the
		* domain.
		@@ -7679,6 +7684,13 @@ static int need_active_balance(struct lb_env *env)
		return 1;
		}

		if ((capacity_of(env->src_cpu) < capacity_of(env->dst_cpu)) &&
		env->src_rq->cfs.h_nr_running == 1 &&
		cpu_overutilized(env->src_cpu) &&
		!cpu_overutilized(env->dst_cpu)) {
		return 1;
		}

		return unlikely(sd->nr_balance_failed > sd->cache_nice_tries+2);
		}