From bbdacdfed2f5fa50a2cc9f500a36e05990a0837d Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Thu, 10 Aug 2017 17:10:26 +0200 Subject: [PATCH] sched/debug: Optimize sched_domain sysctl generation Currently we unconditionally destroy all sysctl bits and regenerate them after we've rebuild the domains (even if that rebuild is a no-op). And since we unconditionally (re)build the sysctl for all possible CPUs, onlining all CPUs gets us O(n^2) time. Instead change this to only rebuild the bits for CPUs we've actually installed new domains on. Reported-by: Ofer Levi(SW) Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Signed-off-by: Ingo Molnar --- kernel/sched/debug.c | 68 ++++++++++++++++++++++++++++++++--------- kernel/sched/sched.h | 4 +++ kernel/sched/topology.c | 1 + 3 files changed, 59 insertions(+), 14 deletions(-) diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index cfd84f79e075..4a23bbc3111b 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -327,38 +327,78 @@ static struct ctl_table *sd_alloc_ctl_cpu_table(int cpu) return table; } +static cpumask_var_t sd_sysctl_cpus; static struct ctl_table_header *sd_sysctl_header; + void register_sched_domain_sysctl(void) { - int i, cpu_num = num_possible_cpus(); - struct ctl_table *entry = sd_alloc_ctl_entry(cpu_num + 1); + static struct ctl_table *cpu_entries; + static struct ctl_table **cpu_idx; char buf[32]; + int i; - WARN_ON(sd_ctl_dir[0].child); - sd_ctl_dir[0].child = entry; + if (!cpu_entries) { + cpu_entries = sd_alloc_ctl_entry(num_possible_cpus() + 1); + if (!cpu_entries) + return; - if (entry == NULL) - return; + WARN_ON(sd_ctl_dir[0].child); + sd_ctl_dir[0].child = cpu_entries; + } - for_each_possible_cpu(i) { - snprintf(buf, 32, "cpu%d", i); - entry->procname = kstrdup(buf, GFP_KERNEL); - entry->mode = 0555; - entry->child = sd_alloc_ctl_cpu_table(i); - entry++; + if (!cpu_idx) { + struct ctl_table *e = cpu_entries; + + cpu_idx = kcalloc(nr_cpu_ids, sizeof(struct ctl_table*), GFP_KERNEL); + if (!cpu_idx) + return; + + /* deal with sparse possible map */ + for_each_possible_cpu(i) { + cpu_idx[i] = e; + e++; + } + } + + if (!cpumask_available(sd_sysctl_cpus)) { + if (!alloc_cpumask_var(&sd_sysctl_cpus, GFP_KERNEL)) + return; + + /* init to possible to not have holes in @cpu_entries */ + cpumask_copy(sd_sysctl_cpus, cpu_possible_mask); + } + + for_each_cpu(i, sd_sysctl_cpus) { + struct ctl_table *e = cpu_idx[i]; + + if (e->child) + sd_free_ctl_entry(&e->child); + + if (!e->procname) { + snprintf(buf, 32, "cpu%d", i); + e->procname = kstrdup(buf, GFP_KERNEL); + } + e->mode = 0555; + e->child = sd_alloc_ctl_cpu_table(i); + + __cpumask_clear_cpu(i, sd_sysctl_cpus); } WARN_ON(sd_sysctl_header); sd_sysctl_header = register_sysctl_table(sd_ctl_root); } +void dirty_sched_domain_sysctl(int cpu) +{ + if (cpumask_available(sd_sysctl_cpus)) + __cpumask_set_cpu(cpu, sd_sysctl_cpus); +} + /* may be called multiple times per register */ void unregister_sched_domain_sysctl(void) { unregister_sysctl_table(sd_sysctl_header); sd_sysctl_header = NULL; - if (sd_ctl_dir[0].child) - sd_free_ctl_entry(&sd_ctl_dir[0].child); } #endif /* CONFIG_SYSCTL */ #endif /* CONFIG_SMP */ diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index eeef1a3086d1..25e5cb1107f3 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -1120,11 +1120,15 @@ extern int group_balance_cpu(struct sched_group *sg); #if defined(CONFIG_SCHED_DEBUG) && defined(CONFIG_SYSCTL) void register_sched_domain_sysctl(void); +void dirty_sched_domain_sysctl(int cpu); void unregister_sched_domain_sysctl(void); #else static inline void register_sched_domain_sysctl(void) { } +static inline void dirty_sched_domain_sysctl(int cpu) +{ +} static inline void unregister_sched_domain_sysctl(void) { } diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c index 727daa2a0abe..6f7b43982f73 100644 --- a/kernel/sched/topology.c +++ b/kernel/sched/topology.c @@ -459,6 +459,7 @@ cpu_attach_domain(struct sched_domain *sd, struct root_domain *rd, int cpu) rq_attach_root(rq, rd); tmp = rq->sd; rcu_assign_pointer(rq->sd, sd); + dirty_sched_domain_sysctl(cpu); destroy_sched_domains(tmp); update_top_cache_domain(cpu); -- 2.20.1