diff options
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/sched/core.c | 70 | ||||
| -rw-r--r-- | kernel/sched/debug.c | 13 | ||||
| -rw-r--r-- | kernel/sched/features.h | 2 | ||||
| -rw-r--r-- | kernel/sched/sched.h | 10 |
4 files changed, 94 insertions, 1 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index e6c714b9b211..fcb35ae15619 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -58,7 +58,17 @@ const_debug unsigned int sysctl_sched_features = #include "features.h" 0; #undef SCHED_FEAT -#endif + +/* + * Print a warning if need_resched is set for the given duration (if + * LATENCY_WARN is enabled). + * + * If sysctl_resched_latency_warn_once is set, only one warning will be shown + * per boot. + */ +__read_mostly int sysctl_resched_latency_warn_ms = 100; +__read_mostly int sysctl_resched_latency_warn_once = 1; +#endif /* CONFIG_SCHED_DEBUG */ /* * Number of tasks to iterate in a single balance run. @@ -4527,6 +4537,55 @@ unsigned long long task_sched_runtime(struct task_struct *p) return ns; } +#ifdef CONFIG_SCHED_DEBUG +static u64 cpu_resched_latency(struct rq *rq) +{ + int latency_warn_ms = READ_ONCE(sysctl_resched_latency_warn_ms); + u64 resched_latency, now = rq_clock(rq); + static bool warned_once; + + if (sysctl_resched_latency_warn_once && warned_once) + return 0; + + if (!need_resched() || !latency_warn_ms) + return 0; + + if (system_state == SYSTEM_BOOTING) + return 0; + + if (!rq->last_seen_need_resched_ns) { + rq->last_seen_need_resched_ns = now; + rq->ticks_without_resched = 0; + return 0; + } + + rq->ticks_without_resched++; + resched_latency = now - rq->last_seen_need_resched_ns; + if (resched_latency <= latency_warn_ms * NSEC_PER_MSEC) + return 0; + + warned_once = true; + + return resched_latency; +} + +static int __init setup_resched_latency_warn_ms(char *str) +{ + long val; + + if ((kstrtol(str, 0, &val))) { + pr_warn("Unable to set resched_latency_warn_ms\n"); + return 1; + } + + sysctl_resched_latency_warn_ms = val; + return 1; +} +__setup("resched_latency_warn_ms=", setup_resched_latency_warn_ms); +#else +static inline u64 cpu_resched_latency(struct rq *rq) { return 0; } +#endif /* CONFIG_SCHED_DEBUG */ + /* * This function gets called by the timer code, with HZ frequency. * We call it with interrupts disabled. @@ -4538,6 +4597,7 @@ void scheduler_tick(void) struct task_struct *curr = rq->curr; struct rq_flags rf; unsigned long thermal_pressure; + u64 resched_latency; arch_scale_freq_tick(); sched_clock_tick(); @@ -4548,10 +4608,15 @@ void scheduler_tick(void) thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq)); update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure); curr->sched_class->task_tick(rq, curr, 0); + if (sched_feat(LATENCY_WARN)) + resched_latency = cpu_resched_latency(rq); calc_global_load_tick(rq); rq_unlock(rq, &rf); + if (sched_feat(LATENCY_WARN) && resched_latency) + resched_latency_warn(cpu, resched_latency); + perf_event_task_tick(); #ifdef CONFIG_SMP @@ -5046,6 +5111,9 @@ static void __sched notrace __schedule(bool preempt) next = pick_next_task(rq, prev, &rf); clear_tsk_need_resched(prev); clear_preempt_need_resched(); +#ifdef CONFIG_SCHED_DEBUG + rq->last_seen_need_resched_ns = 0; +#endif if (likely(prev != next)) { rq->nr_switches++; diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 461342f598ef..7251fc477a11 100644 --- a/kernel/sched/debug.c +++ b/kernel/sched/debug.c @@ -309,6 +309,9 @@ static __init int sched_init_debug(void) debugfs_create_u32("min_granularity_ns", 0644, debugfs_sched, &sysctl_sched_min_granularity); debugfs_create_u32("wakeup_granularity_ns", 0644, debugfs_sched, &sysctl_sched_wakeup_granularity); + debugfs_create_u32("latency_warn_ms", 0644, debugfs_sched, &sysctl_resched_latency_warn_ms); + debugfs_create_u32("latency_warn_once", 0644, debugfs_sched, &sysctl_resched_latency_warn_once); + #ifdef CONFIG_SMP debugfs_create_file("tunable_scaling", 0644, debugfs_sched, NULL, &sched_scaling_fops); debugfs_create_u32("migration_cost_ns", 0644, debugfs_sched, &sysctl_sched_migration_cost); @@ -1027,3 +1030,13 @@ void proc_sched_set_task(struct task_struct *p) memset(&p->se.statistics, 0, sizeof(p->se.statistics)); #endif } + +void resched_latency_warn(int cpu, u64 latency) +{ + static DEFINE_RATELIMIT_STATE(latency_check_ratelimit, 60 * 60 * HZ, 1); + + WARN(__ratelimit(&latency_check_ratelimit), + "sched: CPU %d need_resched set for > %llu ns (%d ticks) " + "without schedule\n", + cpu, latency, cpu_rq(cpu)->ticks_without_resched); +} diff --git a/kernel/sched/features.h b/kernel/sched/features.h index 011c5ec7b7b5..7f8dace0964c 100644 --- a/kernel/sched/features.h +++ b/kernel/sched/features.h @@ -91,5 +91,7 @@ SCHED_FEAT(WA_BIAS, true) SCHED_FEAT(UTIL_EST, true) SCHED_FEAT(UTIL_EST_FASTUP, true) +SCHED_FEAT(LATENCY_WARN, false) + SCHED_FEAT(ALT_PERIOD, true) SCHED_FEAT(BASE_SLICE, true) diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index bde72482cbb8..a189bec13729 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -58,6 +58,7 @@ #include <linux/prefetch.h> #include <linux/profile.h> #include <linux/psi.h> +#include <linux/ratelimit.h> #include <linux/rcupdate_wait.h> #include <linux/security.h> #include <linux/stop_machine.h> @@ -971,6 +972,11 @@ struct rq { atomic_t nr_iowait; +#ifdef CONFIG_SCHED_DEBUG + u64 last_seen_need_resched_ns; + int ticks_without_resched; +#endif + #ifdef CONFIG_MEMBARRIER int membarrier_state; #endif @@ -2371,6 +2377,8 @@ extern void print_dl_stats(struct seq_file *m, int cpu); extern void print_cfs_rq(struct seq_file *m, int cpu, struct cfs_rq *cfs_rq); extern void print_rt_rq(struct seq_file *m, int cpu, struct rt_rq *rt_rq); extern void print_dl_rq(struct seq_file *m, int cpu, struct dl_rq *dl_rq); + +extern void resched_latency_warn(int cpu, u64 latency); #ifdef CONFIG_NUMA_BALANCING extern void show_numa_stats(struct task_struct *p, struct seq_file *m); @@ -2378,6 +2386,8 @@ extern void print_numa_stats(struct seq_file *m, int node, unsigned long tsf, unsigned long tpf, unsigned long gsf, unsigned long gpf); #endif /* CONFIG_NUMA_BALANCING */ +#else +static inline void resched_latency_warn(int cpu, u64 latency) {} #endif /* CONFIG_SCHED_DEBUG */ extern void init_cfs_rq(struct cfs_rq *cfs_rq); |