[RFC PATCH] Tracepoint sched probes

[Mathieu Desnoyers]

** note : early RFC. This patch applies on a unreleased LTTng for
2.6.26-rc8 patchset.

Scheduler tracepoint probes

Only a single probe is implement as a POC.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxx>
CC: 'Peter Zijlstra' <peterz@xxxxxxxxxxxxx>
CC: "Frank Ch. Eigler" <fche@xxxxxxxxxx>
CC: 'Ingo Molnar' <mingo@xxxxxxx>
CC: 'Hideo AOKI' <haoki@xxxxxxxxxx>
CC: Takashi Nishiie <t-nishiie@xxxxxxxxxxxxxxxxxx>
CC: 'Steven Rostedt' <rostedt@xxxxxxxxxxx>
---
 init/Kconfig         |    7 +++++++
 kernel/Makefile      |    1 +
 kernel/sched-trace.c |   28 ++++++++++++++++++++++++++++
 kernel/sched-trace.h |   11 +++++++++++
 kernel/sched.c       |    5 +++--
 5 files changed, 50 insertions(+), 2 deletions(-)

Index: linux-2.6.26-rc7-lttng/kernel/sched-trace.c
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.26-rc7-lttng/kernel/sched-trace.c	2008-06-25 18:36:11.000000000 -0400
@@ -0,0 +1,28 @@
+#include <linux/module.h>
+#include "sched-trace.h"
+
+static void probe_sched_switch(void *private_data, struct task_struct *prev,
+	struct task_struct *next)
+{
+	trace_mark(kernel_sched_schedule,
+		"prev_pid %d next_pid %d prev_state %ld",
+		prev->pid, next->pid, prev->state);
+}
+
+int __init sched_trace_init(void)
+{
+	return register_trace_sched_switch(probe_sched_switch, NULL);
+}
+
+module_init(sched_trace_init);
+
+void __exit sched_trace_exit(void)
+{
+	unregister_trace_sched_switch(probe_sched_switch, NULL);
+}
+
+module_exit(sched_trace_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Mathieu Desnoyers");
+MODULE_DESCRIPTION("Scheduler Tracpoint Probes");
Index: linux-2.6.26-rc7-lttng/kernel/sched-trace.h
===================================================================
--- /dev/null	1970-01-01 00:00:00.000000000 +0000
+++ linux-2.6.26-rc7-lttng/kernel/sched-trace.h	2008-06-25 18:36:11.000000000 -0400
@@ -0,0 +1,11 @@
+#ifndef _KERNEL_SCHED_TRACE_H
+#define _KERNEL_SCHED_TRACE_H
+
+#include <linux/sched.h>
+#include <linux/tracepoint.h>
+
+DEFINE_TRACE(sched_switch,
+	TPPROTO(struct task_struct *prev, struct task_struct *next),
+	TPARGS(prev, next));
+
+#endif
Index: linux-2.6.26-rc7-lttng/kernel/sched.c
===================================================================
--- linux-2.6.26-rc7-lttng.orig/kernel/sched.c	2008-06-25 18:35:42.000000000 -0400
+++ linux-2.6.26-rc7-lttng/kernel/sched.c	2008-06-25 18:36:11.000000000 -0400
@@ -75,6 +75,8 @@
 #include <asm/tlb.h>
 #include <asm/irq_regs.h>
 
+#include "sched-trace.h"
+
 /*
  * Convert user-nice values [ -20 ... 0 ... 19 ]
  * to static priority [ MAX_RT_PRIO..MAX_PRIO-1 ],
@@ -2458,8 +2460,7 @@
 	struct mm_struct *mm, *oldmm;
 
 	prepare_task_switch(rq, prev, next);
-	trace_mark(internal_kernel_sched_schedule,
-		"prev %p next %p", prev, next);
+	trace_sched_switch(prev, next);
 	mm = next->mm;
 	oldmm = prev->active_mm;
 	/*
Index: linux-2.6.26-rc7-lttng/kernel/Makefile
===================================================================
--- linux-2.6.26-rc7-lttng.orig/kernel/Makefile	2008-06-25 18:35:42.000000000 -0400
+++ linux-2.6.26-rc7-lttng/kernel/Makefile	2008-06-25 18:36:11.000000000 -0400
@@ -70,6 +70,7 @@
 obj-$(USE_IMMEDIATE) += immediate.o
 obj-$(CONFIG_MARKERS) += marker.o
 obj-$(CONFIG_TRACEPOINTS) += tracepoint.o
+obj-$(CONFIG_SCHED_TRACE) += sched-trace.o
 obj-$(CONFIG_LATENCYTOP) += latencytop.o
 
 ifneq ($(CONFIG_SCHED_NO_NO_OMIT_FRAME_POINTER),y)
Index: linux-2.6.26-rc7-lttng/init/Kconfig
===================================================================
--- linux-2.6.26-rc7-lttng.orig/init/Kconfig	2008-06-25 18:36:07.000000000 -0400
+++ linux-2.6.26-rc7-lttng/init/Kconfig	2008-06-25 18:36:26.000000000 -0400
@@ -789,6 +789,13 @@
 	  Place an empty function call at each tracepoint site. Can be
 	  dynamically changed for a probe function.
 
+config SCHED_TRACE
+	depends on TRACEPOINTS
+	tristate "Scheduler tracing"
+	default y
+	help
+	  Build the scheduler tracing probes.
+
 config MARKERS
 	bool "Activate markers"
 	help

-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
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