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Message-Id: <20180521142505.6522-9-quentin.perret@arm.com>
Date: Mon, 21 May 2018 15:25:03 +0100
From: Quentin Perret <quentin.perret@....com>
To: peterz@...radead.org, rjw@...ysocki.net,
gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
linux-pm@...r.kernel.org
Cc: mingo@...hat.com, dietmar.eggemann@....com,
morten.rasmussen@....com, chris.redpath@....com,
patrick.bellasi@....com, valentin.schneider@....com,
vincent.guittot@...aro.org, thara.gopinath@...aro.org,
viresh.kumar@...aro.org, tkjos@...gle.com, joelaf@...gle.com,
smuckle@...gle.com, adharmap@...cinc.com, skannan@...cinc.com,
pkondeti@...eaurora.org, juri.lelli@...hat.com,
edubezval@...il.com, srinivas.pandruvada@...ux.intel.com,
currojerez@...eup.net, javi.merino@...nel.org,
quentin.perret@....com
Subject: [RFC PATCH v3 08/10] sched: Lowest energy aware balancing sched_domain level pointer
Add another member to the family of per-cpu sched_domain shortcut
pointers. This one, sd_ea, points to the lowest level at which energy
aware scheduling should be used.
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_ea shortcut is wired to the lowest
scheduling domain at which the SD_ASYM_CPUCAPACITY flag is set. For
example, it is possible to apply energy-aware scheduling within a socket
on a multi-socket system, as long as each socket has an asymmetric
topology. Cross-sockets wake-up balancing will only happen when the
system is over-utilized, or this_cpu and prev_cpu are in different
sockets.
cc: Ingo Molnar <mingo@...hat.com>
cc: Peter Zijlstra <peterz@...radead.org>
Suggested-by: Morten Rasmussen <morten.rasmussen@....com>
Signed-off-by: Quentin Perret <quentin.perret@....com>
---
kernel/sched/sched.h | 1 +
kernel/sched/topology.c | 4 ++++
2 files changed, 5 insertions(+)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 0dd895554f78..31535198f545 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1151,6 +1151,7 @@ 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_ea);
struct sched_group_capacity {
atomic_t ref;
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 3e22c798f18d..8e7ee37771bb 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -398,6 +398,7 @@ 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_ea);
static void update_top_cache_domain(int cpu)
{
@@ -423,6 +424,9 @@ static void update_top_cache_domain(int cpu)
sd = highest_flag_domain(cpu, SD_ASYM_PACKING);
rcu_assign_pointer(per_cpu(sd_asym, cpu), sd);
+
+ sd = lowest_flag_domain(cpu, SD_ASYM_CPUCAPACITY);
+ rcu_assign_pointer(per_cpu(sd_ea, cpu), sd);
}
/*
--
2.17.0
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