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Commit a4dffa6a authored by Quentin Perret's avatar Quentin Perret
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FROMLIST: sched/topology: Lowest CPU asymmetry sched_domain level pointer 



Add another member to the family of per-cpu sched_domain shortcut
pointers. This one, sd_asym_cpucapacity, points to the lowest level
at which the SD_ASYM_CPUCAPACITY flag is set. While at it, rename the
sd_asym shortcut to sd_asym_packing to avoid confusions.

Generally speaking, the largest opportunity to save energy via
scheduling comes from a smarter exploitation of heterogeneous platforms
(i.e. big.LITTLE). Consequently, the sd_asym_cpucapacity shortcut will
be used at first as the lowest domain where Energy-Aware Scheduling
(EAS) should be applied. For example, it is possible to apply EAS within
a socket on a multi-socket system, as long as each socket has an
asymmetric topology. Energy-aware cross-sockets wake-up balancing can
only happen if this_cpu and prev_cpu are in different sockets.

Change-Id: Ie777a1733991d40ce063b318e915199ba3c5416a
cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>
Suggested-by: default avatarMorten Rasmussen <morten.rasmussen@arm.com>
Signed-off-by: default avatarQuentin Perret <quentin.perret@arm.com>
Message-Id: <20181016101513.26919-7-quentin.perret@arm.com>
Signed-off-by: default avatarQuentin Perret <quentin.perret@arm.com>
parent 2b73358b

kernel/sched/fair.c

+1 −1
Original line number Diff line number Diff line
@@ -9269,7 +9269,7 @@ static void nohz_balancer_kick(struct rq *rq) 
		}

	}



	sd = rcu_dereference(per_cpu(sd_asym, cpu));

	sd = rcu_dereference(per_cpu(sd_asym_packing, cpu));

	if (sd) {

		for_each_cpu(i, sched_domain_span(sd)) {

			if (i == cpu ||

kernel/sched/sched.h

+2 −1
Original line number Diff line number Diff line
@@ -1206,7 +1206,8 @@ DECLARE_PER_CPU(int, sd_llc_size); 
DECLARE_PER_CPU(int, sd_llc_id);

DECLARE_PER_CPU(struct sched_domain_shared *, sd_llc_shared);

DECLARE_PER_CPU(struct sched_domain *, sd_numa);

DECLARE_PER_CPU(struct sched_domain *, sd_asym);

DECLARE_PER_CPU(struct sched_domain *, sd_asym_packing);

DECLARE_PER_CPU(struct sched_domain *, sd_asym_cpucapacity);

extern struct static_key_false sched_asym_cpucapacity;



struct sched_group_capacity {

kernel/sched/topology.c

+6 −2
Original line number Diff line number Diff line
@@ -508,7 +508,8 @@ DEFINE_PER_CPU(int, sd_llc_size); 
DEFINE_PER_CPU(int, sd_llc_id);

DEFINE_PER_CPU(struct sched_domain_shared *, sd_llc_shared);

DEFINE_PER_CPU(struct sched_domain *, sd_numa);

DEFINE_PER_CPU(struct sched_domain *, sd_asym);

DEFINE_PER_CPU(struct sched_domain *, sd_asym_packing);

DEFINE_PER_CPU(struct sched_domain *, sd_asym_cpucapacity);

DEFINE_STATIC_KEY_FALSE(sched_asym_cpucapacity);



static void update_top_cache_domain(int cpu)
@@ -534,7 +535,10 @@ static void update_top_cache_domain(int cpu) 
	rcu_assign_pointer(per_cpu(sd_numa, cpu), sd);



	sd = highest_flag_domain(cpu, SD_ASYM_PACKING);

	rcu_assign_pointer(per_cpu(sd_asym, cpu), sd);

	rcu_assign_pointer(per_cpu(sd_asym_packing, cpu), sd);



	sd = lowest_flag_domain(cpu, SD_ASYM_CPUCAPACITY);

	rcu_assign_pointer(per_cpu(sd_asym_cpucapacity, cpu), sd);

}



/*