From fbd705a0c6184580d0e2fbcbd47a37b6e5822511 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 9 Jun 2015 11:13:36 +0200 Subject: [PATCH] sched: Introduce the 'trace_sched_waking' tracepoint Mathieu reported that since 317f394160e9 ("sched: Move the second half of ttwu() to the remote cpu") trace_sched_wakeup() can happen out of context of the waker. This is a problem when you want to analyse wakeup paths because it is now very hard to correlate the wakeup event to whoever issued the wakeup. OTOH trace_sched_wakeup() is issued at the point where we set p->state = TASK_RUNNING, which is right were we hand the task off to the scheduler, so this is an important point when looking at scheduling behaviour, up to here its been the wakeup path everything hereafter is due to scheduler policy. To bridge this gap, introduce a second tracepoint: trace_sched_waking. It is guaranteed to be called in the waker context. Reported-by: Mathieu Desnoyers Signed-off-by: Peter Zijlstra (Intel) Cc: Francis Giraldeau Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner Link: http://lkml.kernel.org/r/20150609091336.GQ3644@twins.programming.kicks-ass.net Signed-off-by: Ingo Molnar --- include/trace/events/sched.h | 30 +++++++++++++++++++++--------- kernel/sched/core.c | 10 +++++++--- kernel/trace/trace_sched_switch.c | 2 +- kernel/trace/trace_sched_wakeup.c | 2 +- 4 files changed, 30 insertions(+), 14 deletions(-) diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h index d57a575fe31f..539d6bc3216a 100644 --- a/include/trace/events/sched.h +++ b/include/trace/events/sched.h @@ -55,9 +55,9 @@ TRACE_EVENT(sched_kthread_stop_ret, */ DECLARE_EVENT_CLASS(sched_wakeup_template, - TP_PROTO(struct task_struct *p, int success), + TP_PROTO(struct task_struct *p), - TP_ARGS(__perf_task(p), success), + TP_ARGS(__perf_task(p)), TP_STRUCT__entry( __array( char, comm, TASK_COMM_LEN ) @@ -71,25 +71,37 @@ DECLARE_EVENT_CLASS(sched_wakeup_template, memcpy(__entry->comm, p->comm, TASK_COMM_LEN); __entry->pid = p->pid; __entry->prio = p->prio; - __entry->success = success; + __entry->success = 1; /* rudiment, kill when possible */ __entry->target_cpu = task_cpu(p); ), - TP_printk("comm=%s pid=%d prio=%d success=%d target_cpu=%03d", + TP_printk("comm=%s pid=%d prio=%d target_cpu=%03d", __entry->comm, __entry->pid, __entry->prio, - __entry->success, __entry->target_cpu) + __entry->target_cpu) ); +/* + * Tracepoint called when waking a task; this tracepoint is guaranteed to be + * called from the waking context. + */ +DEFINE_EVENT(sched_wakeup_template, sched_waking, + TP_PROTO(struct task_struct *p), + TP_ARGS(p)); + +/* + * Tracepoint called when the task is actually woken; p->state == TASK_RUNNNG. + * It it not always called from the waking context. + */ DEFINE_EVENT(sched_wakeup_template, sched_wakeup, - TP_PROTO(struct task_struct *p, int success), - TP_ARGS(p, success)); + TP_PROTO(struct task_struct *p), + TP_ARGS(p)); /* * Tracepoint for waking up a new task: */ DEFINE_EVENT(sched_wakeup_template, sched_wakeup_new, - TP_PROTO(struct task_struct *p, int success), - TP_ARGS(p, success)); + TP_PROTO(struct task_struct *p), + TP_ARGS(p)); #ifdef CREATE_TRACE_POINTS static inline long __trace_sched_switch_state(struct task_struct *p) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 48be7dc3d497..fa5826cc612f 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1654,9 +1654,9 @@ static void ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags) { check_preempt_curr(rq, p, wake_flags); - trace_sched_wakeup(p, true); - p->state = TASK_RUNNING; + trace_sched_wakeup(p); + #ifdef CONFIG_SMP if (p->sched_class->task_woken) { /* @@ -1874,6 +1874,8 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) if (!(p->state & state)) goto out; + trace_sched_waking(p); + success = 1; /* we're going to change ->state */ cpu = task_cpu(p); @@ -1949,6 +1951,8 @@ static void try_to_wake_up_local(struct task_struct *p) if (!(p->state & TASK_NORMAL)) goto out; + trace_sched_waking(p); + if (!task_on_rq_queued(p)) ttwu_activate(rq, p, ENQUEUE_WAKEUP); @@ -2307,7 +2311,7 @@ void wake_up_new_task(struct task_struct *p) rq = __task_rq_lock(p); activate_task(rq, p, 0); p->on_rq = TASK_ON_RQ_QUEUED; - trace_sched_wakeup_new(p, true); + trace_sched_wakeup_new(p); check_preempt_curr(rq, p, WF_FORK); #ifdef CONFIG_SMP if (p->sched_class->task_woken) diff --git a/kernel/trace/trace_sched_switch.c b/kernel/trace/trace_sched_switch.c index 419ca37e72c9..f270088e9929 100644 --- a/kernel/trace/trace_sched_switch.c +++ b/kernel/trace/trace_sched_switch.c @@ -26,7 +26,7 @@ probe_sched_switch(void *ignore, struct task_struct *prev, struct task_struct *n } static void -probe_sched_wakeup(void *ignore, struct task_struct *wakee, int success) +probe_sched_wakeup(void *ignore, struct task_struct *wakee) { if (unlikely(!sched_ref)) return; diff --git a/kernel/trace/trace_sched_wakeup.c b/kernel/trace/trace_sched_wakeup.c index 9b33dd117f3f..12cbe77b4136 100644 --- a/kernel/trace/trace_sched_wakeup.c +++ b/kernel/trace/trace_sched_wakeup.c @@ -514,7 +514,7 @@ static void wakeup_reset(struct trace_array *tr) } static void -probe_wakeup(void *ignore, struct task_struct *p, int success) +probe_wakeup(void *ignore, struct task_struct *p) { struct trace_array_cpu *data; int cpu = smp_processor_id(); -- 2.20.1