From mboxrd@z Thu Jan 1 00:00:00 1970 From: Quentin Perret Subject: [PATCH v9 09/15] sched: Introduce sched_energy_present static key Date: Mon, 19 Nov 2018 14:18:51 +0000 Message-ID: <20181119141857.8625-10-quentin.perret@arm.com> References: <20181119141857.8625-1-quentin.perret@arm.com> Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <20181119141857.8625-1-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@codeaurora.org, skannan@codeaurora.org, 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 In order to make sure Energy Aware Scheduling (EAS) will not impact systems where no Energy Model is available, introduce a static key guarding the access to EAS code. Since EAS is enabled on a per-root-domain basis, the static key is enabled when at least one root domain meets all conditions for EAS. Cc: Ingo Molnar Cc: Peter Zijlstra Signed-off-by: Quentin Perret --- kernel/sched/sched.h | 4 ++++ kernel/sched/topology.c | 31 +++++++++++++++++++++++++++++++ 2 files changed, 35 insertions(+) diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index 0278b251c379..5b636a8aa900 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -2298,3 +2298,7 @@ unsigned long scale_irq_capacity(unsigned long util, unsigned long irq, unsigned #else #define perf_domain_span(pd) NULL #endif + +#ifdef CONFIG_SMP +extern struct static_key_false sched_energy_present; +#endif diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index 70492d4bfed6..1457ef80ee94 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -201,6 +201,7 @@ sd_parent_degenerate(struct sched_domain *sd, struct sched_domain *parent) return 1; } +DEFINE_STATIC_KEY_FALSE(sched_energy_present); #if defined(CONFIG_ENERGY_MODEL) && defined(CONFIG_CPU_FREQ_GOV_SCHEDUTIL) DEFINE_MUTEX(sched_energy_mutex); bool sched_energy_update; @@ -273,6 +274,35 @@ static void destroy_perf_domain_rcu(struct rcu_head *rp) free_pd(pd); } +static void sched_energy_start(int ndoms_new, cpumask_var_t doms_new[]) +{ + /* + * The conditions for EAS to start are checked during the creation of + * root domains. If one of them meets all conditions, it will have a + * non-null list of performance domains. + */ + while (ndoms_new) { + if (cpu_rq(cpumask_first(doms_new[ndoms_new - 1]))->rd->pd) + goto enable; + ndoms_new--; + } + + if (static_branch_unlikely(&sched_energy_present)) { + if (sched_debug()) + pr_info("%s: stopping EAS\n", __func__); + static_branch_disable_cpuslocked(&sched_energy_present); + } + + return; + +enable: + if (!static_branch_unlikely(&sched_energy_present)) { + if (sched_debug()) + pr_info("%s: starting EAS\n", __func__); + static_branch_enable_cpuslocked(&sched_energy_present); + } +} + /* * EAS can be used on a root domain if it meets all the following conditions: * 1. an Energy Model (EM) is available; @@ -2187,6 +2217,7 @@ void partition_sched_domains(int ndoms_new, cpumask_var_t doms_new[], match3: ; } + sched_energy_start(ndoms_new, doms_new); #endif /* Remember the new sched domains: */ -- 2.19.1