linux-kernel - [tip:sched/core] sched/topology: Add lowest CPU asymmetry sched

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Message-ID: <tip-011b27bb5d3139e8b5fe9ceff1fc7f6dc3145071@git.kernel.org>
Date:   Tue, 11 Dec 2018 07:34:57 -0800
From:   tip-bot for Quentin Perret <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     hpa@...or.com, quentin.perret@....com, tglx@...utronix.de,
        mingo@...nel.org, linux-kernel@...r.kernel.org,
        peterz@...radead.org, morten.rasmussen@....com,
        torvalds@...ux-foundation.org, efault@....de
Subject: [tip:sched/core] sched/topology: Add lowest CPU asymmetry
 sched_domain level pointer

Commit-ID:  011b27bb5d3139e8b5fe9ceff1fc7f6dc3145071
Gitweb:     https://git.kernel.org/tip/011b27bb5d3139e8b5fe9ceff1fc7f6dc3145071
Author:     Quentin Perret <quentin.perret@....com>
AuthorDate: Mon, 3 Dec 2018 09:56:19 +0000
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 11 Dec 2018 15:16:59 +0100

sched/topology: Add 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 will
only happen when the system is over-utilized, or this_cpu and prev_cpu
are in different sockets.

Suggested-by: Morten Rasmussen <morten.rasmussen@....com>
Signed-off-by: Quentin Perret <quentin.perret@....com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Mike Galbraith <efault@....de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: adharmap@...eaurora.org
Cc: chris.redpath@....com
Cc: currojerez@...eup.net
Cc: dietmar.eggemann@....com
Cc: edubezval@...il.com
Cc: gregkh@...uxfoundation.org
Cc: javi.merino@...nel.org
Cc: joel@...lfernandes.org
Cc: juri.lelli@...hat.com
Cc: patrick.bellasi@....com
Cc: pkondeti@...eaurora.org
Cc: rjw@...ysocki.net
Cc: skannan@...eaurora.org
Cc: smuckle@...gle.com
Cc: srinivas.pandruvada@...ux.intel.com
Cc: thara.gopinath@...aro.org
Cc: tkjos@...gle.com
Cc: valentin.schneider@....com
Cc: vincent.guittot@...aro.org
Cc: viresh.kumar@...aro.org
Link: https://lkml.kernel.org/r/20181203095628.11858-7-quentin.perret@arm.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/sched/fair.c     | 2 +-
 kernel/sched/sched.h    | 3 ++-
 kernel/sched/topology.c | 8 ++++++--
 3 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index fdc8356ea742..a31a6d325901 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -9299,7 +9299,7 @@ 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 ||
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 808a565187b1..75c403674706 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1303,7 +1303,8 @@ 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 {
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 169d25cafab5..137ccfed9a43 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -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);
 }
 
 /*