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Subject[RFC PATCH] Tracepoint sched probes
** 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@polymtl.ca>
CC: 'Peter Zijlstra' <peterz@infradead.org>
CC: "Frank Ch. Eigler" <fche@redhat.com>
CC: 'Ingo Molnar' <mingo@elte.hu>
CC: 'Hideo AOKI' <haoki@redhat.com>
CC: Takashi Nishiie <t-nishiie@np.css.fujitsu.com>
CC: 'Steven Rostedt' <rostedt@goodmis.org>
---
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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