From 7a31b5cce774cd17698b5062061c5a2522e1bdd7 Mon Sep 17 00:00:00 2001 From: Morten Rasmussen Date: Thu, 18 Dec 2014 14:47:18 +0000 Subject: [PATCH] sched: Calculate energy consumption of sched_group For energy-aware load-balancing decisions it is necessary to know the energy consumption estimates of groups of cpus. This patch introduces a basic function, sched_group_energy(), which estimates the energy consumption of the cpus in the group and any resources shared by the members of the group. NOTE: The function has five levels of identation and breaks the 80 character limit. Refactoring is necessary. cc: Ingo Molnar cc: Peter Zijlstra Signed-off-by: Morten Rasmussen --- kernel/sched/core.c | 4 ++ kernel/sched/fair.c | 156 +++++++++++++++++++++++++++++++++++++++++++ kernel/sched/sched.h | 1 + 3 files changed, 161 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 9d82f4c47e3b..a8f33eedbe8f 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -5994,6 +5994,7 @@ DEFINE_PER_CPU(struct sched_domain *, sd_numa); DEFINE_PER_CPU(struct sched_domain *, sd_busy); DEFINE_PER_CPU(struct sched_domain *, sd_asym); DEFINE_PER_CPU(struct sched_domain *, sd_ea); +DEFINE_PER_CPU(struct sched_domain *, sd_scs); static void update_top_cache_domain(int cpu) { @@ -6027,6 +6028,9 @@ static void update_top_cache_domain(int cpu) break; } rcu_assign_pointer(per_cpu(sd_ea, cpu), ea_sd); + + sd = highest_flag_domain(cpu, SD_SHARE_CAP_STATES); + rcu_assign_pointer(per_cpu(sd_scs, cpu), sd); } /* diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 318141042a3e..49f7567c6b07 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -4701,6 +4701,162 @@ static inline bool energy_aware(void) return sched_feat(ENERGY_AWARE); } +/* + * cpu_norm_util() returns the cpu util relative to a specific capacity, + * i.e. it's busy ratio, in the range [0..SCHED_LOAD_SCALE] which is useful for + * energy calculations. Using the scale-invariant util returned by + * cpu_util() and approximating scale-invariant util by: + * + * util ~ (curr_freq/max_freq)*1024 * capacity_orig/1024 * running_time/time + * + * the normalized util can be found using the specific capacity. + * + * capacity = capacity_orig * curr_freq/max_freq + * + * norm_util = running_time/time ~ util/capacity + */ +static unsigned long cpu_norm_util(int cpu, unsigned long capacity) +{ + int util = cpu_util(cpu); + + if (util >= capacity) + return SCHED_CAPACITY_SCALE; + + return (util << SCHED_CAPACITY_SHIFT)/capacity; +} + +static unsigned long group_max_util(struct sched_group *sg) +{ + int i; + unsigned long max_util = 0; + + for_each_cpu(i, sched_group_cpus(sg)) + max_util = max(max_util, cpu_util(i)); + + return max_util; +} + +/* + * group_norm_util() returns the approximated group util relative to it's + * current capacity (busy ratio) in the range [0..SCHED_LOAD_SCALE] for use in + * energy calculations. Since task executions may or may not overlap in time in + * the group the true normalized util is between max(cpu_norm_util(i)) and + * sum(cpu_norm_util(i)) when iterating over all cpus in the group, i. The + * latter is used as the estimate as it leads to a more pessimistic energy + * estimate (more busy). + */ +static unsigned long group_norm_util(struct sched_group *sg, int cap_idx) +{ + int i; + unsigned long util_sum = 0; + unsigned long capacity = sg->sge->cap_states[cap_idx].cap; + + for_each_cpu(i, sched_group_cpus(sg)) + util_sum += cpu_norm_util(i, capacity); + + if (util_sum > SCHED_CAPACITY_SCALE) + return SCHED_CAPACITY_SCALE; + return util_sum; +} + +static int find_new_capacity(struct sched_group *sg, + const struct sched_group_energy const *sge) +{ + int idx; + unsigned long util = group_max_util(sg); + + for (idx = 0; idx < sge->nr_cap_states; idx++) { + if (sge->cap_states[idx].cap >= util) + return idx; + } + + return idx; +} + +/* + * sched_group_energy(): Computes the absolute energy consumption of cpus + * belonging to the sched_group including shared resources shared only by + * members of the group. Iterates over all cpus in the hierarchy below the + * sched_group starting from the bottom working it's way up before going to + * the next cpu until all cpus are covered at all levels. The current + * implementation is likely to gather the same util statistics multiple times. + * This can probably be done in a faster but more complex way. + * Note: sched_group_energy() may fail when racing with sched_domain updates. + */ +static int sched_group_energy(struct sched_group *sg_top) +{ + struct sched_domain *sd; + int cpu, total_energy = 0; + struct cpumask visit_cpus; + struct sched_group *sg; + + WARN_ON(!sg_top->sge); + + cpumask_copy(&visit_cpus, sched_group_cpus(sg_top)); + + while (!cpumask_empty(&visit_cpus)) { + struct sched_group *sg_shared_cap = NULL; + + cpu = cpumask_first(&visit_cpus); + + /* + * Is the group utilization affected by cpus outside this + * sched_group? + */ + sd = rcu_dereference(per_cpu(sd_scs, cpu)); + + if (!sd) + /* + * We most probably raced with hotplug; returning a + * wrong energy estimation is better than entering an + * infinite loop. + */ + return -EINVAL; + + if (sd->parent) + sg_shared_cap = sd->parent->groups; + + for_each_domain(cpu, sd) { + sg = sd->groups; + + /* Has this sched_domain already been visited? */ + if (sd->child && group_first_cpu(sg) != cpu) + break; + + do { + struct sched_group *sg_cap_util; + unsigned long group_util; + int sg_busy_energy, sg_idle_energy, cap_idx; + + if (sg_shared_cap && sg_shared_cap->group_weight >= sg->group_weight) + sg_cap_util = sg_shared_cap; + else + sg_cap_util = sg; + + cap_idx = find_new_capacity(sg_cap_util, sg->sge); + group_util = group_norm_util(sg, cap_idx); + sg_busy_energy = (group_util * sg->sge->cap_states[cap_idx].power) + >> SCHED_CAPACITY_SHIFT; + sg_idle_energy = ((SCHED_LOAD_SCALE-group_util) * sg->sge->idle_states[0].power) + >> SCHED_CAPACITY_SHIFT; + + total_energy += sg_busy_energy + sg_idle_energy; + + if (!sd->child) + cpumask_xor(&visit_cpus, &visit_cpus, sched_group_cpus(sg)); + + if (cpumask_equal(sched_group_cpus(sg), sched_group_cpus(sg_top))) + goto next_cpu; + + } while (sg = sg->next, sg != sd->groups); + } +next_cpu: + continue; + } + + return total_energy; +} + /* * Detect M:N waker/wakee relationships via a switching-frequency heuristic. * A waker of many should wake a different task than the one last awakened diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index a77516a15ba0..a618db2936d4 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -840,6 +840,7 @@ DECLARE_PER_CPU(struct sched_domain *, sd_numa); DECLARE_PER_CPU(struct sched_domain *, sd_busy); DECLARE_PER_CPU(struct sched_domain *, sd_asym); DECLARE_PER_CPU(struct sched_domain *, sd_ea); +DECLARE_PER_CPU(struct sched_domain *, sd_scs); struct sched_group_capacity { atomic_t ref; -- 2.34.1