Instead of providing asynchronous checks for the nohz subsystem to verify perf event tick dependency, migrate perf to the new mask.
Perf needs the tick for two situations: 1) Freq events. We could set the tick dependency when those are installed on a CPU context. But setting a global dependency on top of the global freq events accounting is much easier. If people want that to be optimized, we can still refine that on the per-CPU tick dependency level. This patch dooesn't change the current behaviour anyway. 2) Throttled events: this is a per-cpu dependency. Cc: Christoph Lameter <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Preeti U Murthy <[email protected]> Cc: Rik van Riel <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Viresh Kumar <[email protected]> Signed-off-by: Frederic Weisbecker <[email protected]> --- include/linux/perf_event.h | 6 ------ kernel/events/core.c | 19 +++++-------------- kernel/time/tick-sched.c | 6 ------ 3 files changed, 5 insertions(+), 26 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 2027809..ff25348 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -1013,12 +1013,6 @@ static inline int __perf_event_disable(void *info) { return -1; } static inline void perf_event_task_tick(void) { } #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/kernel/events/core.c b/kernel/events/core.c index d3dae34..9980bd9 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -3064,17 +3064,6 @@ 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); @@ -3085,6 +3074,7 @@ void perf_event_task_tick(void) __this_cpu_inc(perf_throttled_seq); throttled = __this_cpu_xchg(perf_throttled_count, 0); + tick_nohz_clear_tick_dependency_this_cpu(TICK_PERF_EVENTS_BIT); list_for_each_entry_safe(ctx, tmp, head, active_ctx_list) perf_adjust_freq_unthr_context(ctx, throttled); @@ -3453,7 +3443,8 @@ 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); + if (atomic_dec_and_test(&nr_freq_events)) + tick_nohz_clear_tick_dependency(TICK_PERF_EVENTS_BIT); if (is_cgroup_event(event)) static_key_slow_dec_deferred(&perf_sched_events); if (has_branch_stack(event)) @@ -6089,9 +6080,9 @@ 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_nohz_set_tick_dependency_this_cpu(TICK_PERF_EVENTS_BIT); hwc->interrupts = MAX_INTERRUPTS; perf_log_throttle(event, 0); - tick_nohz_full_kick(); ret = 1; } } @@ -7477,7 +7468,7 @@ static void account_event(struct perf_event *event) atomic_inc(&nr_task_events); if (event->attr.freq) { if (atomic_inc_return(&nr_freq_events) == 1) - tick_nohz_full_kick_all(); + tick_nohz_set_tick_dependency(TICK_PERF_EVENTS_BIT); } if (has_branch_stack(event)) static_key_slow_inc(&perf_sched_events.key); diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index a64646e..fbe4736 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> @@ -203,11 +202,6 @@ static bool can_stop_full_tick(struct tick_sched *ts) return false; } - if (!perf_event_can_stop_tick()) { - trace_tick_stop(0, "perf events running\n"); - return false; - } - #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK /* * sched_clock_tick() needs us? -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
