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FROMLIST: sched/topology: Lowest CPU asymmetry sched_domain level pointer

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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: Morten Rasmussen <morten.rasmussen@arm.com>
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
Message-Id: <20181016101513.26919-7-quentin.perret@arm.com>
Signed-off-by: Quentin Perret <quentin.perret@arm.com>
This commit is contained in:
Quentin Perret 2018-10-16 11:15:04 +01:00
parent 2b73358bce
commit a4dffa6a32
3 changed files with 9 additions and 4 deletions
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2
kernel/sched/fair.c
View File

@ -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 ||

3
kernel/sched/sched.h
View File

@ -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 {

8
kernel/sched/topology.c
View File

@ -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);
}
/*