diff options
| -rw-r--r-- | include/linux/atomic.h | 21 | ||||
| -rw-r--r-- | include/linux/perf_event.h | 6 | ||||
| -rw-r--r-- | include/linux/posix-timers.h | 3 | ||||
| -rw-r--r-- | include/linux/sched.h | 11 | ||||
| -rw-r--r-- | include/linux/tick.h | 97 | ||||
| -rw-r--r-- | include/trace/events/timer.h | 36 | ||||
| -rw-r--r-- | kernel/events/core.c | 65 | ||||
| -rw-r--r-- | kernel/sched/clock.c | 5 | ||||
| -rw-r--r-- | kernel/sched/core.c | 49 | ||||
| -rw-r--r-- | kernel/sched/rt.c | 16 | ||||
| -rw-r--r-- | kernel/sched/sched.h | 48 | ||||
| -rw-r--r-- | kernel/time/posix-cpu-timers.c | 52 | ||||
| -rw-r--r-- | kernel/time/tick-sched.c | 175 | ||||
| -rw-r--r-- | kernel/time/tick-sched.h | 1 |
14 files changed, 424 insertions, 161 deletions
diff --git a/include/linux/atomic.h b/include/linux/atomic.h index 301de78..6c502cb 100644 --- a/include/linux/atomic.h +++ b/include/linux/atomic.h @@ -548,6 +548,27 @@ static inline int atomic_dec_if_positive(atomic_t *v) } #endif +/** + * fetch_or - perform *ptr |= mask and return old value of *ptr + * @ptr: pointer to value + * @mask: mask to OR on the value + * + * cmpxchg based fetch_or, macro so it works for different integer types + */ +#ifndef fetch_or +#define fetch_or(ptr, mask) \ +({ typeof(*(ptr)) __old, __val = *(ptr); \ + for (;;) { \ + __old = cmpxchg((ptr), __val, __val | (mask)); \ + if (__old == __val) \ + break; \ + __val = __old; \ + } \ + __old; \ +}) +#endif + + #ifdef CONFIG_GENERIC_ATOMIC64 #include <asm-generic/atomic64.h> #endif diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index a9d8cab..79ec7bb 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1110,12 +1110,6 @@ static inline void perf_event_task_tick(void) { } static inline int perf_event_release_kernel(struct perf_event *event) { return 0; } #endif -#if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_NO_HZ_FULL) -extern bool perf_event_can_stop_tick(void); -#else -static inline bool perf_event_can_stop_tick(void) { return true; } -#endif - #if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_CPU_SUP_INTEL) extern void perf_restore_debug_store(void); #else diff --git a/include/linux/posix-timers.h b/include/linux/posix-timers.h index 907f3fd..62d44c1 100644 --- a/include/linux/posix-timers.h +++ b/include/linux/posix-timers.h @@ -128,9 +128,6 @@ void posix_cpu_timer_schedule(struct k_itimer *timer); void run_posix_cpu_timers(struct task_struct *task); void posix_cpu_timers_exit(struct task_struct *task); void posix_cpu_timers_exit_group(struct task_struct *task); - -bool posix_cpu_timers_can_stop_tick(struct task_struct *tsk); - void set_process_cpu_timer(struct task_struct *task, unsigned int clock_idx, cputime_t *newval, cputime_t *oldval); diff --git a/include/linux/sched.h b/include/linux/sched.h index 838a89a..c617ea12 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -717,6 +717,10 @@ struct signal_struct { /* Earliest-expiration cache. */ struct task_cputime cputime_expires; +#ifdef CONFIG_NO_HZ_FULL + unsigned long tick_dep_mask; +#endif + struct list_head cpu_timers[3]; struct pid *tty_old_pgrp; @@ -1542,6 +1546,10 @@ struct task_struct { VTIME_SYS, } vtime_snap_whence; #endif + +#ifdef CONFIG_NO_HZ_FULL + unsigned long tick_dep_mask; +#endif unsigned long nvcsw, nivcsw; /* context switch counts */ u64 start_time; /* monotonic time in nsec */ u64 real_start_time; /* boot based time in nsec */ @@ -2356,10 +2364,7 @@ static inline void wake_up_nohz_cpu(int cpu) { } #endif #ifdef CONFIG_NO_HZ_FULL -extern bool sched_can_stop_tick(void); extern u64 scheduler_tick_max_deferment(void); -#else -static inline bool sched_can_stop_tick(void) { return false; } #endif #ifdef CONFIG_SCHED_AUTOGROUP diff --git a/include/linux/tick.h b/include/linux/tick.h index 97fd4e5..21f7364 100644 --- a/include/linux/tick.h +++ b/include/linux/tick.h @@ -97,6 +97,19 @@ static inline void tick_broadcast_exit(void) tick_broadcast_oneshot_control(TICK_BROADCAST_EXIT); } +enum tick_dep_bits { + TICK_DEP_BIT_POSIX_TIMER = 0, + TICK_DEP_BIT_PERF_EVENTS = 1, + TICK_DEP_BIT_SCHED = 2, + TICK_DEP_BIT_CLOCK_UNSTABLE = 3 +}; + +#define TICK_DEP_MASK_NONE 0 +#define TICK_DEP_MASK_POSIX_TIMER (1 << TICK_DEP_BIT_POSIX_TIMER) +#define TICK_DEP_MASK_PERF_EVENTS (1 << TICK_DEP_BIT_PERF_EVENTS) +#define TICK_DEP_MASK_SCHED (1 << TICK_DEP_BIT_SCHED) +#define TICK_DEP_MASK_CLOCK_UNSTABLE (1 << TICK_DEP_BIT_CLOCK_UNSTABLE) + #ifdef CONFIG_NO_HZ_COMMON extern int tick_nohz_enabled; extern int tick_nohz_tick_stopped(void); @@ -154,9 +167,73 @@ static inline int housekeeping_any_cpu(void) return cpumask_any_and(housekeeping_mask, cpu_online_mask); } -extern void tick_nohz_full_kick(void); +extern void tick_nohz_dep_set(enum tick_dep_bits bit); +extern void tick_nohz_dep_clear(enum tick_dep_bits bit); +extern void tick_nohz_dep_set_cpu(int cpu, enum tick_dep_bits bit); +extern void tick_nohz_dep_clear_cpu(int cpu, enum tick_dep_bits bit); +extern void tick_nohz_dep_set_task(struct task_struct *tsk, + enum tick_dep_bits bit); +extern void tick_nohz_dep_clear_task(struct task_struct *tsk, + enum tick_dep_bits bit); +extern void tick_nohz_dep_set_signal(struct signal_struct *signal, + enum tick_dep_bits bit); +extern void tick_nohz_dep_clear_signal(struct signal_struct *signal, + enum tick_dep_bits bit); + +/* + * The below are tick_nohz_[set,clear]_dep() wrappers that optimize off-cases + * on top of static keys. + */ +static inline void tick_dep_set(enum tick_dep_bits bit) +{ + if (tick_nohz_full_enabled()) + tick_nohz_dep_set(bit); +} + +static inline void tick_dep_clear(enum tick_dep_bits bit) +{ + if (tick_nohz_full_enabled()) + tick_nohz_dep_clear(bit); +} + +static inline void tick_dep_set_cpu(int cpu, enum tick_dep_bits bit) +{ + if (tick_nohz_full_cpu(cpu)) + tick_nohz_dep_set_cpu(cpu, bit); +} + +static inline void tick_dep_clear_cpu(int cpu, enum tick_dep_bits bit) +{ + if (tick_nohz_full_cpu(cpu)) + tick_nohz_dep_clear_cpu(cpu, bit); +} + +static inline void tick_dep_set_task(struct task_struct *tsk, + enum tick_dep_bits bit) +{ + if (tick_nohz_full_enabled()) + tick_nohz_dep_set_task(tsk, bit); +} +static inline void tick_dep_clear_task(struct task_struct *tsk, + enum tick_dep_bits bit) +{ + if (tick_nohz_full_enabled()) + tick_nohz_dep_clear_task(tsk, bit); +} +static inline void tick_dep_set_signal(struct signal_struct *signal, + enum tick_dep_bits bit) +{ + if (tick_nohz_full_enabled()) + tick_nohz_dep_set_signal(signal, bit); +} +static inline void tick_dep_clear_signal(struct signal_struct *signal, + enum tick_dep_bits bit) +{ + if (tick_nohz_full_enabled()) + tick_nohz_dep_clear_signal(signal, bit); +} + extern void tick_nohz_full_kick_cpu(int cpu); -extern void tick_nohz_full_kick_all(void); extern void __tick_nohz_task_switch(void); #else static inline int housekeeping_any_cpu(void) @@ -166,9 +243,21 @@ static inline int housekeeping_any_cpu(void) static inline bool tick_nohz_full_enabled(void) { return false; } static inline bool tick_nohz_full_cpu(int cpu) { return false; } static inline void tick_nohz_full_add_cpus_to(struct cpumask *mask) { } + +static inline void tick_dep_set(enum tick_dep_bits bit) { } +static inline void tick_dep_clear(enum tick_dep_bits bit) { } +static inline void tick_dep_set_cpu(int cpu, enum tick_dep_bits bit) { } +static inline void tick_dep_clear_cpu(int cpu, enum tick_dep_bits bit) { } +static inline void tick_dep_set_task(struct task_struct *tsk, + enum tick_dep_bits bit) { } +static inline void tick_dep_clear_task(struct task_struct *tsk, + enum tick_dep_bits bit) { } +static inline void tick_dep_set_signal(struct signal_struct *signal, + enum tick_dep_bits bit) { } +static inline void tick_dep_clear_signal(struct signal_struct *signal, + enum tick_dep_bits bit) { } + static inline void tick_nohz_full_kick_cpu(int cpu) { } -static inline void tick_nohz_full_kick(void) { } -static inline void tick_nohz_full_kick_all(void) { } static inline void __tick_nohz_task_switch(void) { } #endif diff --git a/include/trace/events/timer.h b/include/trace/events/timer.h index 073b9ac..5144013 100644 --- a/include/trace/events/timer.h +++ b/include/trace/events/timer.h @@ -328,23 +328,49 @@ TRACE_EVENT(itimer_expire, ); #ifdef CONFIG_NO_HZ_COMMON + +#define TICK_DEP_NAMES \ + tick_dep_name(NONE) \ + tick_dep_name(POSIX_TIMER) \ + tick_dep_name(PERF_EVENTS) \ + tick_dep_name(SCHED) \ + tick_dep_name_end(CLOCK_UNSTABLE) + +#undef tick_dep_name +#undef tick_dep_name_end + +#define tick_dep_name(sdep) TRACE_DEFINE_ENUM(TICK_DEP_MASK_##sdep); +#define tick_dep_name_end(sdep) TRACE_DEFINE_ENUM(TICK_DEP_MASK_##sdep); + +TICK_DEP_NAMES + +#undef tick_dep_name +#undef tick_dep_name_end + +#define tick_dep_name(sdep) { TICK_DEP_MASK_##sdep, #sdep }, +#define tick_dep_name_end(sdep) { TICK_DEP_MASK_##sdep, #sdep } + +#define show_tick_dep_name(val) \ + __print_symbolic(val, TICK_DEP_NAMES) + TRACE_EVENT(tick_stop, - TP_PROTO(int success, char *error_msg), + TP_PROTO(int success, int dependency), - TP_ARGS(success, error_msg), + TP_ARGS(success, dependency), TP_STRUCT__entry( __field( int , success ) - __string( msg, error_msg ) + __field( int , dependency ) ), TP_fast_assign( __entry->success = success; - __assign_str(msg, error_msg); + __entry->dependency = dependency; ), - TP_printk("success=%s msg=%s", __entry->success ? "yes" : "no", __get_str(msg)) + TP_printk("success=%d dependency=%s", __entry->success, \ + show_tick_dep_name(__entry->dependency)) ); #endif diff --git a/kernel/events/core.c b/kernel/events/core.c index b723149..712570d 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3112,17 +3112,6 @@ done: return rotate; } -#ifdef CONFIG_NO_HZ_FULL -bool perf_event_can_stop_tick(void) -{ - if (atomic_read(&nr_freq_events) || - __this_cpu_read(perf_throttled_count)) - return false; - else - return true; -} -#endif - void perf_event_task_tick(void) { struct list_head *head = this_cpu_ptr(&active_ctx_list); @@ -3133,6 +3122,7 @@ void perf_event_task_tick(void) __this_cpu_inc(perf_throttled_seq); throttled = __this_cpu_xchg(perf_throttled_count, 0); + tick_dep_clear_cpu(smp_processor_id(), TICK_DEP_BIT_PERF_EVENTS); list_for_each_entry_safe(ctx, tmp, head, active_ctx_list) perf_adjust_freq_unthr_context(ctx, throttled); @@ -3564,6 +3554,28 @@ static void unaccount_event_cpu(struct perf_event *event, int cpu) atomic_dec(&per_cpu(perf_cgroup_events, cpu)); } +#ifdef CONFIG_NO_HZ_FULL +static DEFINE_SPINLOCK(nr_freq_lock); +#endif + +static void unaccount_freq_event_nohz(void) +{ +#ifdef CONFIG_NO_HZ_FULL + spin_lock(&nr_freq_lock); + if (atomic_dec_and_test(&nr_freq_events)) + tick_nohz_dep_clear(TICK_DEP_BIT_PERF_EVENTS); + spin_unlock(&nr_freq_lock); +#endif +} + +static void unaccount_freq_event(void) +{ + if (tick_nohz_full_enabled()) + unaccount_freq_event_nohz(); + else + atomic_dec(&nr_freq_events); +} + static void unaccount_event(struct perf_event *event) { bool dec = false; @@ -3580,7 +3592,7 @@ static void unaccount_event(struct perf_event *event) if (event->attr.task) atomic_dec(&nr_task_events); if (event->attr.freq) - atomic_dec(&nr_freq_events); + unaccount_freq_event(); if (event->attr.context_switch) { dec = true; atomic_dec(&nr_switch_events); @@ -6424,9 +6436,9 @@ static int __perf_event_overflow(struct perf_event *event, if (unlikely(throttle && hwc->interrupts >= max_samples_per_tick)) { __this_cpu_inc(perf_throttled_count); + tick_dep_set_cpu(smp_processor_id(), TICK_DEP_BIT_PERF_EVENTS); hwc->interrupts = MAX_INTERRUPTS; perf_log_throttle(event, 0); - tick_nohz_full_kick(); ret = 1; } } @@ -7815,6 +7827,27 @@ static void account_event_cpu(struct perf_event *event, int cpu) atomic_inc(&per_cpu(perf_cgroup_events, cpu)); } +/* Freq events need the tick to stay alive (see perf_event_task_tick). */ +static void account_freq_event_nohz(void) +{ +#ifdef CONFIG_NO_HZ_FULL + /* Lock so we don't race with concurrent unaccount */ + spin_lock(&nr_freq_lock); + if (atomic_inc_return(&nr_freq_events) == 1) + tick_nohz_dep_set(TICK_DEP_BIT_PERF_EVENTS); + spin_unlock(&nr_freq_lock); +#endif +} + +static void account_freq_event(void) +{ + if (tick_nohz_full_enabled()) + account_freq_event_nohz(); + else + atomic_inc(&nr_freq_events); +} + + static void account_event(struct perf_event *event) { bool inc = false; @@ -7830,10 +7863,8 @@ static void account_event(struct perf_event *event) atomic_inc(&nr_comm_events); if (event->attr.task) atomic_inc(&nr_task_events); - if (event->attr.freq) { - if (atomic_inc_return(&nr_freq_events) == 1) - tick_nohz_full_kick_all(); - } + if (event->attr.freq) + account_freq_event(); if (event->attr.context_switch) { atomic_inc(&nr_switch_events); inc = true; diff --git a/kernel/sched/clock.c b/kernel/sched/clock.c index bc54e84..fedb967 100644 --- a/kernel/sched/clock.c +++ b/kernel/sched/clock.c @@ -61,6 +61,7 @@ #include <linux/static_key.h> #include <linux/workqueue.h> #include <linux/compiler.h> +#include <linux/tick.h> /* * Scheduler clock - returns current time in nanosec units. @@ -89,6 +90,8 @@ static void __set_sched_clock_stable(void) { if (!sched_clock_stable()) static_key_slow_inc(&__sched_clock_stable); + + tick_dep_clear(TICK_DEP_BIT_CLOCK_UNSTABLE); } void set_sched_clock_stable(void) @@ -108,6 +111,8 @@ static void __clear_sched_clock_stable(struct work_struct *work) /* XXX worry about clock continuity */ if (sched_clock_stable()) static_key_slow_dec(&__sched_clock_stable); + + tick_dep_set(TICK_DEP_BIT_CLOCK_UNSTABLE); } static DECLARE_WORK(sched_clock_work, __clear_sched_clock_stable); diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 05114b1..e5725b9 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -320,20 +320,6 @@ static inline void init_hrtick(void) } #endif /* CONFIG_SCHED_HRTICK */ -/* - * cmpxchg based fetch_or, macro so it works for different integer types - */ -#define fetch_or(ptr, val) \ -({ typeof(*(ptr)) __old, __val = *(ptr); \ - for (;;) { \ - __old = cmpxchg((ptr), __val, __val | (val)); \ - if (__old == __val) \ - break; \ - __val = __old; \ - } \ - __old; \ -}) - #if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG) /* * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG, @@ -582,31 +568,36 @@ static inline bool got_nohz_idle_kick(void) #endif /* CONFIG_NO_HZ_COMMON */ #ifdef CONFIG_NO_HZ_FULL -bool sched_can_stop_tick(void) +bool sched_can_stop_tick(struct rq *rq) { + int fifo_nr_running; + + /* Deadline tasks, even if single, need the tick */ + if (rq->dl.dl_nr_running) + return false; + /* - * FIFO realtime policy runs the highest priority task. Other runnable - * tasks are of a lower priority. The scheduler tick does nothing. + * FIFO realtime policy runs the highest priority task (after DEADLINE). + * Other runnable tasks are of a lower priority. The scheduler tick + * isn't needed. */ - if (current->policy == SCHED_FIFO) + fifo_nr_running = rq->rt.rt_nr_running - rq->rt.rr_nr_running; + if (fifo_nr_running) return true; /* * Round-robin realtime tasks time slice with other tasks at the same - * realtime priority. Is this task the only one at this priority? + * realtime priority. */ - if (current->policy == SCHED_RR) { - struct sched_rt_entity *rt_se = ¤t->rt; - - return list_is_singular(&rt_se->run_list); + if (rq->rt.rr_nr_running) { + if (rq->rt.rr_nr_running == 1) + return true; + else + return false; } - /* - * More than one running task need preemption. - * nr_running update is assumed to be visible - * after IPI is sent from wakers. - */ - if (this_rq()->nr_running > 1) + /* Normal multitasking need periodic preemption checks */ + if (rq->cfs.nr_running > 1) return false; return true; diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c index a774b4d..5624713 100644 --- a/kernel/sched/rt.c +++ b/kernel/sched/rt.c @@ -1150,12 +1150,27 @@ unsigned int rt_se_nr_running(struct sched_rt_entity *rt_se) } static inline +unsigned int rt_se_rr_nr_running(struct sched_rt_entity *rt_se) +{ + struct rt_rq *group_rq = group_rt_rq(rt_se); + struct task_struct *tsk; + + if (group_rq) + return group_rq->rr_nr_running; + + tsk = rt_task_of(rt_se); + + return (tsk->policy == SCHED_RR) ? 1 : 0; +} + +static inline void inc_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq) { int prio = rt_se_prio(rt_se); WARN_ON(!rt_prio(prio)); rt_rq->rt_nr_running += rt_se_nr_running(rt_se); + rt_rq->rr_nr_running += rt_se_rr_nr_running(rt_se); inc_rt_prio(rt_rq, prio); inc_rt_migration(rt_se, rt_rq); @@ -1168,6 +1183,7 @@ void dec_rt_tasks(struct sched_rt_entity *rt_se, struct rt_rq *rt_rq) WARN_ON(!rt_prio(rt_se_prio(rt_se))); WARN_ON(!rt_rq->rt_nr_running); rt_rq->rt_nr_running -= rt_se_nr_running(rt_se); + rt_rq->rr_nr_running -= rt_se_rr_nr_running(rt_se); dec_rt_prio(rt_rq, rt_se_prio(rt_se)); dec_rt_migration(rt_se, rt_rq); diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index ef5875f..b2ff5a2 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -450,6 +450,7 @@ static inline int rt_bandwidth_enabled(void) struct rt_rq { struct rt_prio_array active; unsigned int rt_nr_running; + unsigned int rr_nr_running; #if defined CONFIG_SMP || defined CONFIG_RT_GROUP_SCHED struct { int curr; /* highest queued rt task prio */ @@ -1313,6 +1314,35 @@ unsigned long to_ratio(u64 period, u64 runtime); extern void init_entity_runnable_average(struct sched_entity *se); +#ifdef CONFIG_NO_HZ_FULL +extern bool sched_can_stop_tick(struct rq *rq); + +/* + * Tick may be needed by tasks in the runqueue depending on their policy and + * requirements. If tick is needed, lets send the target an IPI to kick it out of + * nohz mode if necessary. + */ +static inline void sched_update_tick_dependency(struct rq *rq) +{ + int cpu; + + if (!tick_nohz_full_enabled()) + return; + + cpu = cpu_of(rq); + + if (!tick_nohz_full_cpu(cpu)) + return; + + if (sched_can_stop_tick(rq)) + tick_nohz_dep_clear_cpu(cpu, TICK_DEP_BIT_SCHED); + else + tick_nohz_dep_set_cpu(cpu, TICK_DEP_BIT_SCHED); +} +#else +static inline void sched_update_tick_dependency(struct rq *rq) { } +#endif + static inline void add_nr_running(struct rq *rq, unsigned count) { unsigned prev_nr = rq->nr_running; @@ -1324,26 +1354,16 @@ static inline void add_nr_running(struct rq *rq, unsigned count) if (!rq->rd->overload) rq->rd->overload = true; #endif - -#ifdef CONFIG_NO_HZ_FULL - if (tick_nohz_full_cpu(rq->cpu)) { - /* - * Tick is needed if more than one task runs on a CPU. - * Send the target an IPI to kick it out of nohz mode. - * - * We assume that IPI implies full memory barrier and the - * new value of rq->nr_running is visible on reception - * from the target. - */ - tick_nohz_full_kick_cpu(rq->cpu); - } -#endif } + + sched_update_tick_dependency(rq); } static inline void sub_nr_running(struct rq *rq, unsigned count) { rq->nr_running -= count; + /* Check if we still need preemption */ + sched_update_tick_dependency(rq); } static inline void rq_last_tick_reset(struct rq *rq) diff --git a/kernel/time/posix-cpu-timers.c b/kernel/time/posix-cpu-timers.c index f5e86d2..1cafba8 100644 --- a/kernel/time/posix-cpu-timers.c +++ b/kernel/time/posix-cpu-timers.c @@ -333,7 +333,6 @@ static int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp) return err; } - /* * Validate the clockid_t for a new CPU-clock timer, and initialize the timer. * This is called from sys_timer_create() and do_cpu_nanosleep() with the @@ -517,6 +516,10 @@ static void arm_timer(struct k_itimer *timer) cputime_expires->sched_exp = exp; break; } + if (CPUCLOCK_PERTHREAD(timer->it_clock)) + tick_dep_set_task(p, TICK_DEP_BIT_POSIX_TIMER); + else + tick_dep_set_signal(p->signal, TICK_DEP_BIT_POSIX_TIMER); } } @@ -582,39 +585,6 @@ static int cpu_timer_sample_group(const clockid_t which_clock, return 0; } -#ifdef CONFIG_NO_HZ_FULL -static void nohz_kick_work_fn(struct work_struct *work) -{ - tick_nohz_full_kick_all(); -} - -static DECLARE_WORK(nohz_kick_work, nohz_kick_work_fn); - -/* - * We need the IPIs to be sent from sane process context. - * The posix cpu timers are always set with irqs disabled. - */ -static void posix_cpu_timer_kick_nohz(void) -{ - if (context_tracking_is_enabled()) - schedule_work(&nohz_kick_work); -} - -bool posix_cpu_timers_can_stop_tick(struct task_struct *tsk) -{ - if (!task_cputime_zero(&tsk->cputime_expires)) - return false; - - /* Check if cputimer is running. This is accessed without locking. */ - if (READ_ONCE(tsk->signal->cputimer.running)) - return false; - - return true; -} -#else -static inline void posix_cpu_timer_kick_nohz(void) { } -#endif - /* * Guts of sys_timer_settime for CPU timers. * This is called with the timer locked and interrupts disabled. @@ -761,8 +731,7 @@ static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags, sample_to_timespec(timer->it_clock, old_incr, &old->it_interval); } - if (!ret) - posix_cpu_timer_kick_nohz(); + return ret; } @@ -911,6 +880,8 @@ static void check_thread_timers(struct task_struct *tsk, __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk); } } + if (task_cputime_zero(tsk_expires)) + tick_dep_clear_task(tsk, TICK_DEP_BIT_POSIX_TIMER); } static inline void stop_process_timers(struct signal_struct *sig) @@ -919,6 +890,7 @@ static inline void stop_process_timers(struct signal_struct *sig) /* Turn off cputimer->running. This is done without locking. */ WRITE_ONCE(cputimer->running, false); + tick_dep_clear_signal(sig, TICK_DEP_BIT_POSIX_TIMER); } static u32 onecputick; @@ -1095,8 +1067,6 @@ void posix_cpu_timer_schedule(struct k_itimer *timer) arm_timer(timer); unlock_task_sighand(p, &flags); - /* Kick full dynticks CPUs in case they need to tick on the new timer */ - posix_cpu_timer_kick_nohz(); out: timer->it_overrun_last = timer->it_overrun; timer->it_overrun = -1; @@ -1270,7 +1240,7 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx, } if (!*newval) - goto out; + return; *newval += now; } @@ -1288,8 +1258,8 @@ void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx, tsk->signal->cputime_expires.virt_exp = *newval; break; } -out: - posix_cpu_timer_kick_nohz(); + + tick_dep_set_signal(tsk->signal, TICK_DEP_BIT_POSIX_TIMER); } static int do_cpu_nanosleep(const clockid_t which_clock, int flags, diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index 0b17424..969e670 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -22,7 +22,6 @@ #include <linux/module.h> #include <linux/irq_work.h> #include <linux/posix-timers.h> -#include <linux/perf_event.h> #include <linux/context_tracking.h> #include <asm/irq_regs.h> @@ -158,54 +157,63 @@ static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs) cpumask_var_t tick_nohz_full_mask; cpumask_var_t housekeeping_mask; bool tick_nohz_full_running; +static unsigned long tick_dep_mask; -static bool can_stop_full_tick(void) +static void trace_tick_dependency(unsigned long dep) +{ + if (dep & TICK_DEP_MASK_POSIX_TIMER) { + trace_tick_stop(0, TICK_DEP_MASK_POSIX_TIMER); + return; + } + + if (dep & TICK_DEP_MASK_PERF_EVENTS) { + trace_tick_stop(0, TICK_DEP_MASK_PERF_EVENTS); + return; + } + + if (dep & TICK_DEP_MASK_SCHED) { + trace_tick_stop(0, TICK_DEP_MASK_SCHED); + return; + } + + if (dep & TICK_DEP_MASK_CLOCK_UNSTABLE) + trace_tick_stop(0, TICK_DEP_MASK_CLOCK_UNSTABLE); +} + +static bool can_stop_full_tick(struct tick_sched *ts) { WARN_ON_ONCE(!irqs_disabled()); - if (!sched_can_stop_tick()) { - trace_tick_stop(0, "more than 1 task in runqueue\n"); + if (tick_dep_mask) { + trace_tick_dependency(tick_dep_mask); return false; } - if (!posix_cpu_timers_can_stop_tick(current)) { - trace_tick_stop(0, "posix timers running\n"); + if (ts->tick_dep_mask) { + trace_tick_dependency(ts->tick_dep_mask); return false; } - if (!perf_event_can_stop_tick()) { - trace_tick_stop(0, "perf events running\n"); + if (current->tick_dep_mask) { + trace_tick_dependency(current->tick_dep_mask); return false; } - /* sched_clock_tick() needs us? */ -#ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK - /* - * TODO: kick full dynticks CPUs when - * sched_clock_stable is set. - */ - if (!sched_clock_stable()) { - trace_tick_stop(0, "unstable sched clock\n"); - /* - * Don't allow the user to think they can get - * full NO_HZ with this machine. - */ - WARN_ONCE(tick_nohz_full_running, - "NO_HZ FULL will not work with unstable sched clock"); + if (current->signal->tick_dep_mask) { + trace_tick_dependency(current->signal->tick_dep_mask); return false; } -#endif return true; } -static void nohz_full_kick_work_func(struct irq_work *work) +static void nohz_full_kick_func(struct irq_work *work) { /* Empty, the tick restart happens on tick_nohz_irq_exit() */ } static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = { - .func = nohz_full_kick_work_func, + .func = nohz_full_kick_func, }; /* @@ -214,7 +222,7 @@ static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = { * This kick, unlike tick_nohz_full_kick_cpu() and tick_nohz_full_kick_all(), * is NMI safe. */ -void tick_nohz_full_kick(void) +static void tick_nohz_full_kick(void) { if (!tick_nohz_full_cpu(smp_processor_id())) return; @@ -234,27 +242,112 @@ void tick_nohz_full_kick_cpu(int cpu) irq_work_queue_on(&per_cpu(nohz_full_kick_work, cpu), cpu); } -static void nohz_full_kick_ipi(void *info) -{ - /* Empty, the tick restart happens on tick_nohz_irq_exit() */ -} - /* * Kick all full dynticks CPUs in order to force these to re-evaluate * their dependency on the tick and restart it if necessary. */ -void tick_nohz_full_kick_all(void) +static void tick_nohz_full_kick_all(void) { + int cpu; + if (!tick_nohz_full_running) return; preempt_disable(); - smp_call_function_many(tick_nohz_full_mask, - nohz_full_kick_ipi, NULL, false); - tick_nohz_full_kick(); + for_each_cpu_and(cpu, tick_nohz_full_mask, cpu_online_mask) + tick_nohz_full_kick_cpu(cpu); preempt_enable(); } +static void tick_nohz_dep_set_all(unsigned long *dep, + enum tick_dep_bits bit) +{ + unsigned long prev; + + prev = fetch_or(dep, BIT_MASK(bit)); + if (!prev) + tick_nohz_full_kick_all(); +} + +/* + * Set a global tick dependency. Used by perf events that rely on freq and + * by unstable clock. + */ +void tick_nohz_dep_set(enum tick_dep_bits bit) +{ + tick_nohz_dep_set_all(&tick_dep_mask, bit); +} + +void tick_nohz_dep_clear(enum tick_dep_bits bit) +{ + clear_bit(bit, &tick_dep_mask); +} + +/* + * Set per-CPU tick dependency. Used by scheduler and perf events in order to + * manage events throttling. + */ +void tick_nohz_dep_set_cpu(int cpu, enum tick_dep_bits bit) +{ + unsigned long prev; + struct tick_sched *ts; + + ts = per_cpu_ptr(&tick_cpu_sched, cpu); + + prev = fetch_or(&ts->tick_dep_mask, BIT_MASK(bit)); + if (!prev) { + preempt_disable(); + /* Perf needs local kick that is NMI safe */ + if (cpu == smp_processor_id()) { + tick_nohz_full_kick(); + } else { + /* Remote irq work not NMI-safe */ + if (!WARN_ON_ONCE(in_nmi())) + tick_nohz_full_kick_cpu(cpu); + } + preempt_enable(); + } +} + +void tick_nohz_dep_clear_cpu(int cpu, enum tick_dep_bits bit) +{ + struct tick_sched *ts = per_cpu_ptr(&tick_cpu_sched, cpu); + + clear_bit(bit, &ts->tick_dep_mask); +} + +/* + * Set a per-task tick dependency. Posix CPU timers need this in order to elapse + * per task timers. + */ +void tick_nohz_dep_set_task(struct task_struct *tsk, enum tick_dep_bits bit) +{ + /* + * We could optimize this with just kicking the target running the task + * if that noise matters for nohz full users. + */ + tick_nohz_dep_set_all(&tsk->tick_dep_mask, bit); +} + +void tick_nohz_dep_clear_task(struct task_struct *tsk, enum tick_dep_bits bit) +{ + clear_bit(bit, &tsk->tick_dep_mask); +} + +/* + * Set a per-taskgroup tick dependency. Posix CPU timers need this in order to elapse + * per process timers. + */ +void tick_nohz_dep_set_signal(struct signal_struct *sig, enum tick_dep_bits bit) +{ + tick_nohz_dep_set_all(&sig->tick_dep_mask, bit); +} + +void tick_nohz_dep_clear_signal(struct signal_struct *sig, enum tick_dep_bits bit) +{ + clear_bit(bit, &sig->tick_dep_mask); +} + /* * Re-evaluate the need for the tick as we switch the current task. * It might need the tick due to per task/process properties: @@ -263,15 +356,19 @@ void tick_nohz_full_kick_all(void) void __tick_nohz_task_switch(void) { unsigned long flags; + struct tick_sched *ts; local_irq_save(flags); if (!tick_nohz_full_cpu(smp_processor_id())) goto out; - if (tick_nohz_tick_stopped() && !can_stop_full_tick()) - tick_nohz_full_kick(); + ts = this_cpu_ptr(&tick_cpu_sched); + if (ts->tick_stopped) { + if (current->tick_dep_mask || current->signal->tick_dep_mask) + tick_nohz_full_kick(); + } out: local_irq_restore(flags); } @@ -689,7 +786,7 @@ static ktime_t tick_nohz_stop_sched_tick(struct tick_sched *ts, ts->last_tick = hrtimer_get_expires(&ts->sched_timer); ts->tick_stopped = 1; - trace_tick_stop(1, " "); + trace_tick_stop(1, TICK_DEP_MASK_NONE); } /* @@ -740,7 +837,7 @@ static void tick_nohz_full_update_tick(struct tick_sched *ts) if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE) return; - if (can_stop_full_tick()) + if (can_stop_full_tick(ts)) tick_nohz_stop_sched_tick(ts, ktime_get(), cpu); else if (ts->tick_stopped) tick_nohz_restart_sched_tick(ts, ktime_get(), 1); diff --git a/kernel/time/tick-sched.h b/kernel/time/tick-sched.h index a4a8d4e..eb4e325 100644 --- a/kernel/time/tick-sched.h +++ b/kernel/time/tick-sched.h @@ -60,6 +60,7 @@ struct tick_sched { u64 next_timer; ktime_t idle_expires; int do_timer_last; + unsigned long tick_dep_mask; }; extern struct tick_sched *tick_get_tick_sched(int cpu); |
