From e9d2b064149ff7ef4acbc65a1b9374ac8b218d3e Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Fri, 17 Sep 2010 11:28:50 +0200 Subject: [PATCH] perf: Undo the per cpu-context timer stuff Revert the timer per cpu-context timers because of unfortunate nohz interaction. Fixing that would have been somewhat ugly, so go back to driving things from the regular tick. Provide a jiffies interval feature for people who want slower rotations. Signed-off-by: Peter Zijlstra Cc: Stephane Eranian Cc: Robert Richter Cc: Yinghai Lu LKML-Reference: <20100917093009.519845633@chello.nl> Signed-off-by: Ingo Molnar --- include/linux/perf_event.h | 6 ++- kernel/perf_event.c | 79 +++++++++++++++++++++++--------------- kernel/sched.c | 2 + 3 files changed, 55 insertions(+), 32 deletions(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index 165287fd2cc4..61b1e2d760fd 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -870,8 +870,8 @@ struct perf_cpu_context { struct perf_event_context *task_ctx; int active_oncpu; int exclusive; - u64 timer_interval; - struct hrtimer timer; + struct list_head rotation_list; + int jiffies_interval; }; struct perf_output_handle { @@ -1065,6 +1065,7 @@ extern int perf_swevent_get_recursion_context(void); extern void perf_swevent_put_recursion_context(int rctx); extern void perf_event_enable(struct perf_event *event); extern void perf_event_disable(struct perf_event *event); +extern void perf_event_task_tick(void); #else static inline void perf_event_task_sched_in(struct task_struct *task) { } @@ -1099,6 +1100,7 @@ static inline int perf_swevent_get_recursion_context(void) { return -1; } static inline void perf_swevent_put_recursion_context(int rctx) { } static inline void perf_event_enable(struct perf_event *event) { } static inline void perf_event_disable(struct perf_event *event) { } +static inline void perf_event_task_tick(void) { } #endif #define perf_output_put(handle, x) \ diff --git a/kernel/perf_event.c b/kernel/perf_event.c index 27332e5f51a7..baae1367e945 100644 --- a/kernel/perf_event.c +++ b/kernel/perf_event.c @@ -77,23 +77,22 @@ void perf_pmu_enable(struct pmu *pmu) pmu->pmu_enable(pmu); } +static DEFINE_PER_CPU(struct list_head, rotation_list); + +/* + * perf_pmu_rotate_start() and perf_rotate_context() are fully serialized + * because they're strictly cpu affine and rotate_start is called with IRQs + * disabled, while rotate_context is called from IRQ context. + */ static void perf_pmu_rotate_start(struct pmu *pmu) { struct perf_cpu_context *cpuctx = this_cpu_ptr(pmu->pmu_cpu_context); + struct list_head *head = &__get_cpu_var(rotation_list); - if (hrtimer_active(&cpuctx->timer)) - return; + WARN_ON(!irqs_disabled()); - __hrtimer_start_range_ns(&cpuctx->timer, - ns_to_ktime(cpuctx->timer_interval), 0, - HRTIMER_MODE_REL_PINNED, 0); -} - -static void perf_pmu_rotate_stop(struct pmu *pmu) -{ - struct perf_cpu_context *cpuctx = this_cpu_ptr(pmu->pmu_cpu_context); - - hrtimer_cancel(&cpuctx->timer); + if (list_empty(&cpuctx->rotation_list)) + list_add(&cpuctx->rotation_list, head); } static void get_ctx(struct perf_event_context *ctx) @@ -1607,36 +1606,33 @@ static void rotate_ctx(struct perf_event_context *ctx) } /* - * Cannot race with ->pmu_rotate_start() because this is ran from hardirq - * context, and ->pmu_rotate_start() is called with irqs disabled (both are - * cpu affine, so there are no SMP races). + * perf_pmu_rotate_start() and perf_rotate_context() are fully serialized + * because they're strictly cpu affine and rotate_start is called with IRQs + * disabled, while rotate_context is called from IRQ context. */ -static enum hrtimer_restart perf_event_context_tick(struct hrtimer *timer) +static void perf_rotate_context(struct perf_cpu_context *cpuctx) { - enum hrtimer_restart restart = HRTIMER_NORESTART; - struct perf_cpu_context *cpuctx; + u64 interval = (u64)cpuctx->jiffies_interval * TICK_NSEC; struct perf_event_context *ctx = NULL; - int rotate = 0; - - cpuctx = container_of(timer, struct perf_cpu_context, timer); + int rotate = 0, remove = 1; if (cpuctx->ctx.nr_events) { - restart = HRTIMER_RESTART; + remove = 0; if (cpuctx->ctx.nr_events != cpuctx->ctx.nr_active) rotate = 1; } ctx = cpuctx->task_ctx; if (ctx && ctx->nr_events) { - restart = HRTIMER_RESTART; + remove = 0; if (ctx->nr_events != ctx->nr_active) rotate = 1; } perf_pmu_disable(cpuctx->ctx.pmu); - perf_ctx_adjust_freq(&cpuctx->ctx, cpuctx->timer_interval); + perf_ctx_adjust_freq(&cpuctx->ctx, interval); if (ctx) - perf_ctx_adjust_freq(ctx, cpuctx->timer_interval); + perf_ctx_adjust_freq(ctx, interval); if (!rotate) goto done; @@ -1654,10 +1650,24 @@ static enum hrtimer_restart perf_event_context_tick(struct hrtimer *timer) task_ctx_sched_in(ctx, EVENT_FLEXIBLE); done: + if (remove) + list_del_init(&cpuctx->rotation_list); + perf_pmu_enable(cpuctx->ctx.pmu); - hrtimer_forward_now(timer, ns_to_ktime(cpuctx->timer_interval)); +} + +void perf_event_task_tick(void) +{ + struct list_head *head = &__get_cpu_var(rotation_list); + struct perf_cpu_context *cpuctx, *tmp; - return restart; + WARN_ON(!irqs_disabled()); + + list_for_each_entry_safe(cpuctx, tmp, head, rotation_list) { + if (cpuctx->jiffies_interval == 1 || + !(jiffies % cpuctx->jiffies_interval)) + perf_rotate_context(cpuctx); + } } static int event_enable_on_exec(struct perf_event *event, @@ -5186,9 +5196,8 @@ int perf_pmu_register(struct pmu *pmu) __perf_event_init_context(&cpuctx->ctx); cpuctx->ctx.type = cpu_context; cpuctx->ctx.pmu = pmu; - cpuctx->timer_interval = TICK_NSEC; - hrtimer_init(&cpuctx->timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL); - cpuctx->timer.function = perf_event_context_tick; + cpuctx->jiffies_interval = 1; + INIT_LIST_HEAD(&cpuctx->rotation_list); } got_cpu_context: @@ -6229,6 +6238,7 @@ static void __init perf_event_init_all_cpus(void) for_each_possible_cpu(cpu) { swhash = &per_cpu(swevent_htable, cpu); mutex_init(&swhash->hlist_mutex); + INIT_LIST_HEAD(&per_cpu(rotation_list, cpu)); } } @@ -6248,6 +6258,15 @@ static void __cpuinit perf_event_init_cpu(int cpu) } #ifdef CONFIG_HOTPLUG_CPU +static void perf_pmu_rotate_stop(struct pmu *pmu) +{ + struct perf_cpu_context *cpuctx = this_cpu_ptr(pmu->pmu_cpu_context); + + WARN_ON(!irqs_disabled()); + + list_del_init(&cpuctx->rotation_list); +} + static void __perf_event_exit_context(void *__info) { struct perf_event_context *ctx = __info; diff --git a/kernel/sched.c b/kernel/sched.c index 1c3ea7a55b7b..794819eab9ca 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -3584,6 +3584,8 @@ void scheduler_tick(void) curr->sched_class->task_tick(rq, curr, 0); raw_spin_unlock(&rq->lock); + perf_event_task_tick(); + #ifdef CONFIG_SMP rq->idle_at_tick = idle_cpu(cpu); trigger_load_balance(rq, cpu); -- GitLab