From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752024AbbJYUgP (ORCPT ); Sun, 25 Oct 2015 16:36:15 -0400 Received: from mail.efficios.com ([78.47.125.74]:33118 "EHLO mail.efficios.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751608AbbJYUgN (ORCPT ); Sun, 25 Oct 2015 16:36:13 -0400 From: Mathieu Desnoyers To: Thomas Gleixner Cc: linux-kernel@vger.kernel.org, Peter Zijlstra , Julien Desfossez , Francis Giraldeau , Linus Torvalds , Mike Galbraith , Steven Rostedt , Ingo Molnar , Mathieu Desnoyers Subject: [RFC PATCH 4.1-rt backport] sched: Introduce the 'trace_sched_waking' tracepoint Date: Sun, 25 Oct 2015 16:35:24 -0400 Message-Id: <1445805324-2886-1-git-send-email-mathieu.desnoyers@efficios.com> X-Mailer: git-send-email 2.1.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Peter Zijlstra 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. [ Ported to linux-4.1.y-rt kernel by Mathieu Desnoyers. Resolved conflict: try_to_wake_up_local() does not exist in -rt kernel. Removed its instrumentation hunk. ] Reported-by: Mathieu Desnoyers CC: Julien Desfossez CC: Peter Zijlstra (Intel) Cc: Francis Giraldeau Cc: Linus Torvalds Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Steven Rostedt Cc: Thomas Gleixner CC: Ingo Molnar Link: http://lkml.kernel.org/r/20150609091336.GQ3644@twins.programming.kicks-ass.net Signed-off-by: Mathieu Desnoyers --- Julien Desfossez is currently implementing an in-kernel latency tracker module performing automated latency/deadline analysis, which main target is the real time kernel. In order to follow the wakeup chains, we need the sched_waking tracepoint. This is a backport of this tracepoint to the 4.1-rt kernel. I'm not sure what is the policy regarding patch backport from mainline to -rt kernels, hence the RFC. Thanks, Mathieu --- include/trace/events/sched.h | 30 +++++++++++++++++++++--------- kernel/sched/core.c | 8 +++++--- kernel/trace/trace_sched_switch.c | 2 +- kernel/trace/trace_sched_wakeup.c | 2 +- 4 files changed, 28 insertions(+), 14 deletions(-) diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h index 30fedaf..3b63828 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 799b75b..b8b53df 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1558,9 +1558,9 @@ 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) p->sched_class->task_woken(rq, p); @@ -1784,6 +1784,8 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) if (!(wake_flags & WF_LOCK_SLEEPER)) p->saved_state = TASK_RUNNING; + trace_sched_waking(p); + success = 1; /* we're going to change ->state */ cpu = task_cpu(p); @@ -2188,7 +2190,7 @@ 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 419ca37..f270088 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 d6e1003..79a2a5f 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(); -- 2.1.4