From mboxrd@z Thu Jan 1 00:00:00 1970 From: Quentin Perret Subject: [RFC PATCH v4 06/12] sched/topology: Lowest energy aware balancing sched_domain level pointer Date: Thu, 28 Jun 2018 12:40:37 +0100 Message-ID: <20180628114043.24724-7-quentin.perret@arm.com> References: <20180628114043.24724-1-quentin.perret@arm.com> Return-path: In-Reply-To: <20180628114043.24724-1-quentin.perret@arm.com> Sender: linux-kernel-owner@vger.kernel.org To: peterz@infradead.org, rjw@rjwysocki.net, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org Cc: gregkh@linuxfoundation.org, mingo@redhat.com, dietmar.eggemann@arm.com, morten.rasmussen@arm.com, chris.redpath@arm.com, patrick.bellasi@arm.com, valentin.schneider@arm.com, vincent.guittot@linaro.org, thara.gopinath@linaro.org, viresh.kumar@linaro.org, tkjos@google.com, joel@joelfernandes.org, smuckle@google.com, adharmap@quicinc.com, skannan@quicinc.com, pkondeti@codeaurora.org, juri.lelli@redhat.com, edubezval@gmail.com, srinivas.pandruvada@linux.intel.com, currojerez@riseup.net, javi.merino@kernel.org, quentin.perret@arm.com List-Id: linux-pm@vger.kernel.org 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 cc: Peter Zijlstra Suggested-by: Morten Rasmussen Signed-off-by: Quentin Perret --- 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 7038df9fb713..1c32714aed0d 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1168,6 +1168,7 @@ 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 357eff55c1a7..368669fbf0f0 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -414,6 +414,7 @@ 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) { @@ -439,6 +440,9 @@ 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); } /* -- 2.17.1