From afe06efdf07c12fd9370d5cce5383398cedf6c90 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Tue, 22 Nov 2016 12:23:53 -0800 Subject: [PATCH] sched: Extend scheduler's asym packing We generalize the scheduler's asym packing to provide an ordering of the cpu beyond just the cpu number. This allows the use of the ASYM_PACKING scheduler machinery to move loads to preferred CPU in a sched domain. The preference is defined with the cpu priority given by arch_asym_cpu_priority(cpu). We also record the most preferred cpu in a sched group when we build the cpu's capacity for fast lookup of preferred cpu during load balancing. Co-developed-by: Peter Zijlstra (Intel) Signed-off-by: Tim Chen Acked-by: Peter Zijlstra (Intel) Cc: linux-pm@vger.kernel.org Cc: jolsa@redhat.com Cc: rjw@rjwysocki.net Cc: linux-acpi@vger.kernel.org Cc: Srinivas Pandruvada Cc: bp@suse.de Link: http://lkml.kernel.org/r/0e73ae12737dfaafa46c07066cc7c5d3f1675e46.1479844244.git.tim.c.chen@linux.intel.com Signed-off-by: Thomas Gleixner --- include/linux/sched.h | 2 ++ kernel/sched/core.c | 15 ++++++++++++ kernel/sched/fair.c | 53 +++++++++++++++++++++++++++++-------------- kernel/sched/sched.h | 6 +++++ 4 files changed, 59 insertions(+), 17 deletions(-) diff --git a/include/linux/sched.h b/include/linux/sched.h index 19abba04ceca..fe9a499d5aa4 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1077,6 +1077,8 @@ static inline int cpu_numa_flags(void) } #endif +extern int arch_asym_cpu_priority(int cpu); + struct sched_domain_attr { int relax_domain_level; }; diff --git a/kernel/sched/core.c b/kernel/sched/core.c index dc64bd71ed2b..393759bd526e 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -6303,7 +6303,22 @@ static void init_sched_groups_capacity(int cpu, struct sched_domain *sd) WARN_ON(!sg); do { + int cpu, max_cpu = -1; + sg->group_weight = cpumask_weight(sched_group_cpus(sg)); + + if (!(sd->flags & SD_ASYM_PACKING)) + goto next; + + for_each_cpu(cpu, sched_group_cpus(sg)) { + if (max_cpu < 0) + max_cpu = cpu; + else if (sched_asym_prefer(cpu, max_cpu)) + max_cpu = cpu; + } + sg->asym_prefer_cpu = max_cpu; + +next: sg = sg->next; } while (sg != sd->groups); diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index aa475896782d..18d9e75f1f6e 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -97,6 +97,16 @@ unsigned int normalized_sysctl_sched_wakeup_granularity = 1000000UL; const_debug unsigned int sysctl_sched_migration_cost = 500000UL; +#ifdef CONFIG_SMP +/* + * For asym packing, by default the lower numbered cpu has higher priority. + */ +int __weak arch_asym_cpu_priority(int cpu) +{ + return -cpu; +} +#endif + #ifdef CONFIG_CFS_BANDWIDTH /* * Amount of runtime to allocate from global (tg) to local (per-cfs_rq) pool @@ -7388,16 +7398,18 @@ static bool update_sd_pick_busiest(struct lb_env *env, if (env->idle == CPU_NOT_IDLE) return true; /* - * ASYM_PACKING needs to move all the work to the lowest - * numbered CPUs in the group, therefore mark all groups - * higher than ourself as busy. + * ASYM_PACKING needs to move all the work to the highest + * prority CPUs in the group, therefore mark all groups + * of lower priority than ourself as busy. */ - if (sgs->sum_nr_running && env->dst_cpu < group_first_cpu(sg)) { + if (sgs->sum_nr_running && + sched_asym_prefer(env->dst_cpu, sg->asym_prefer_cpu)) { if (!sds->busiest) return true; - /* Prefer to move from highest possible cpu's work */ - if (group_first_cpu(sds->busiest) < group_first_cpu(sg)) + /* Prefer to move from lowest priority cpu's work */ + if (sched_asym_prefer(sds->busiest->asym_prefer_cpu, + sg->asym_prefer_cpu)) return true; } @@ -7549,8 +7561,8 @@ static int check_asym_packing(struct lb_env *env, struct sd_lb_stats *sds) if (!sds->busiest) return 0; - busiest_cpu = group_first_cpu(sds->busiest); - if (env->dst_cpu > busiest_cpu) + busiest_cpu = sds->busiest->asym_prefer_cpu; + if (sched_asym_prefer(busiest_cpu, env->dst_cpu)) return 0; env->imbalance = DIV_ROUND_CLOSEST( @@ -7888,10 +7900,11 @@ static int need_active_balance(struct lb_env *env) /* * ASYM_PACKING needs to force migrate tasks from busy but - * higher numbered CPUs in order to pack all tasks in the - * lowest numbered CPUs. + * lower priority CPUs in order to pack all tasks in the + * highest priority CPUs. */ - if ((sd->flags & SD_ASYM_PACKING) && env->src_cpu > env->dst_cpu) + if ((sd->flags & SD_ASYM_PACKING) && + sched_asym_prefer(env->dst_cpu, env->src_cpu)) return 1; } @@ -8740,7 +8753,7 @@ static inline bool nohz_kick_needed(struct rq *rq) unsigned long now = jiffies; struct sched_domain_shared *sds; struct sched_domain *sd; - int nr_busy, cpu = rq->cpu; + int nr_busy, i, cpu = rq->cpu; bool kick = false; if (unlikely(rq->idle_balance)) @@ -8791,12 +8804,18 @@ static inline bool nohz_kick_needed(struct rq *rq) } sd = rcu_dereference(per_cpu(sd_asym, cpu)); - if (sd && (cpumask_first_and(nohz.idle_cpus_mask, - sched_domain_span(sd)) < cpu)) { - kick = true; - goto unlock; - } + if (sd) { + for_each_cpu(i, sched_domain_span(sd)) { + if (i == cpu || + !cpumask_test_cpu(i, nohz.idle_cpus_mask)) + continue; + if (sched_asym_prefer(i, cpu)) { + kick = true; + goto unlock; + } + } + } unlock: rcu_read_unlock(); return kick; diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index d7e39317d688..7b34c7826ca5 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -540,6 +540,11 @@ struct dl_rq { #ifdef CONFIG_SMP +static inline bool sched_asym_prefer(int a, int b) +{ + return arch_asym_cpu_priority(a) > arch_asym_cpu_priority(b); +} + /* * We add the notion of a root-domain which will be used to define per-domain * variables. Each exclusive cpuset essentially defines an island domain by @@ -908,6 +913,7 @@ struct sched_group { unsigned int group_weight; struct sched_group_capacity *sgc; + int asym_prefer_cpu; /* cpu of highest priority in group */ /* * The CPUs this group covers.