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Subject[patch 14/16] Tracepoints : add DECLARE_TRACE() and DEFINE_TRACE()
Add DEFINE_TRACE() to tracepoints to let them declare the tracepoint structure
in a single spot for all the kernel. It helps reducing memory consumption,
especially when declaring a lot of tracepoints, e.g. for kmalloc tracing.

*API CHANGE WARNING* : now, DECLARE_TRACE() must be used in headers for
tracepoint declarations rather than DEFINE_TRACE(). This is the sane way to do
it. The name previously used was misleading.

Updates scheduler instrumentation to follow this API change.

Impact: API *CHANGE*. Must update all tracepoint users.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
CC: 'Ingo Molnar' <mingo@elte.hu>
CC: Lai Jiangshan <laijs@cn.fujitsu.com>
---
Documentation/tracepoints.txt | 7 +++++-
include/asm-generic/vmlinux.lds.h | 1
include/linux/tracepoint.h | 35 ++++++++++++++++++++++----------
include/trace/sched.h | 24 ++++++++++-----------
kernel/exit.c | 4 +++
kernel/fork.c | 2 +
kernel/kthread.c | 3 ++
kernel/sched.c | 6 +++++
kernel/signal.c | 2 +
samples/tracepoints/tp-samples-trace.h | 4 +--
samples/tracepoints/tracepoint-sample.c | 3 ++
11 files changed, 66 insertions(+), 25 deletions(-)
Index: linux.trees.git/include/linux/tracepoint.h
===================================================================
--- linux.trees.git.orig/include/linux/tracepoint.h 2008-11-14 17:40:39.000000000 -0500
+++ linux.trees.git/include/linux/tracepoint.h 2008-11-14 17:40:54.000000000 -0500
@@ -24,8 +24,12 @@ struct tracepoint {
const char *name; /* Tracepoint name */
int state; /* State. */
void **funcs;
-} __attribute__((aligned(8)));
-
+} __attribute__((aligned(32))); /*
+ * Aligned on 32 bytes because it is
+ * globally visible and gcc happily
+ * align these on the structure size.
+ * Keep in sync with vmlinux.lds.h.
+ */

#define TPPROTO(args...) args
#define TPARGS(args...) args
@@ -55,15 +59,10 @@ struct tracepoint {
* not add unwanted padding between the beginning of the section and the
* structure. Force alignment to the same alignment as the section start.
*/
-#define DEFINE_TRACE(name, proto, args) \
+#define DECLARE_TRACE(name, proto, args) \
+ extern struct tracepoint __tracepoint_##name; \
static inline void trace_##name(proto) \
{ \
- static const char __tpstrtab_##name[] \
- __attribute__((section("__tracepoints_strings"))) \
- = #name; \
- static struct tracepoint __tracepoint_##name \
- __attribute__((section("__tracepoints"), aligned(8))) = \
- { __tpstrtab_##name, 0, NULL }; \
if (unlikely(__tracepoint_##name.state)) \
__DO_TRACE(&__tracepoint_##name, \
TPPROTO(proto), TPARGS(args)); \
@@ -77,11 +76,23 @@ struct tracepoint {
return tracepoint_probe_unregister(#name, (void *)probe);\
}

+#define DEFINE_TRACE(name) \
+ static const char __tpstrtab_##name[] \
+ __attribute__((section("__tracepoints_strings"))) = #name; \
+ struct tracepoint __tracepoint_##name \
+ __attribute__((section("__tracepoints"), aligned(32))) = \
+ { __tpstrtab_##name, 0, NULL }
+
+#define EXPORT_TRACEPOINT_SYMBOL_GPL(name) \
+ EXPORT_SYMBOL_GPL(__tracepoint_##name)
+#define EXPORT_TRACEPOINT_SYMBOL(name) \
+ EXPORT_SYMBOL(__tracepoint_##name)
+
extern void tracepoint_update_probe_range(struct tracepoint *begin,
struct tracepoint *end);

#else /* !CONFIG_TRACEPOINTS */
-#define DEFINE_TRACE(name, proto, args) \
+#define DECLARE_TRACE(name, proto, args) \
static inline void _do_trace_##name(struct tracepoint *tp, proto) \
{ } \
static inline void trace_##name(proto) \
@@ -95,6 +106,10 @@ extern void tracepoint_update_probe_rang
return -ENOSYS; \
}

+#define DEFINE_TRACE(name)
+#define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
+#define EXPORT_TRACEPOINT_SYMBOL(name)
+
static inline void tracepoint_update_probe_range(struct tracepoint *begin,
struct tracepoint *end)
{ }
Index: linux.trees.git/Documentation/tracepoints.txt
===================================================================
--- linux.trees.git.orig/Documentation/tracepoints.txt 2008-11-14 17:37:14.000000000 -0500
+++ linux.trees.git/Documentation/tracepoints.txt 2008-11-14 17:40:54.000000000 -0500
@@ -42,7 +42,7 @@ In include/trace/subsys.h :

#include <linux/tracepoint.h>

-DEFINE_TRACE(subsys_eventname,
+DECLARE_TRACE(subsys_eventname,
TPPTOTO(int firstarg, struct task_struct *p),
TPARGS(firstarg, p));

@@ -50,6 +50,8 @@ In subsys/file.c (where the tracing stat

#include <trace/subsys.h>

+DEFINE_TRACE(subsys_eventname);
+
void somefct(void)
{
...
@@ -86,6 +88,9 @@ to limit collisions. Tracepoint names ar
considered as being the same whether they are in the core kernel image or in
modules.

+If the tracepoint has to be used in kernel modules, an
+EXPORT_TRACEPOINT_SYMBOL_GPL() or EXPORT_TRACEPOINT_SYMBOL() can be used to
+export the defined tracepoints.

* Probe / tracepoint example

Index: linux.trees.git/samples/tracepoints/tracepoint-sample.c
===================================================================
--- linux.trees.git.orig/samples/tracepoints/tracepoint-sample.c 2008-11-14 17:37:14.000000000 -0500
+++ linux.trees.git/samples/tracepoints/tracepoint-sample.c 2008-11-14 17:40:54.000000000 -0500
@@ -13,6 +13,9 @@
#include <linux/proc_fs.h>
#include "tp-samples-trace.h"

+DEFINE_TRACE(subsys_event);
+DEFINE_TRACE(subsys_eventb);
+
struct proc_dir_entry *pentry_example;

static int my_open(struct inode *inode, struct file *file)
Index: linux.trees.git/samples/tracepoints/tp-samples-trace.h
===================================================================
--- linux.trees.git.orig/samples/tracepoints/tp-samples-trace.h 2008-11-14 17:37:14.000000000 -0500
+++ linux.trees.git/samples/tracepoints/tp-samples-trace.h 2008-11-14 17:40:54.000000000 -0500
@@ -4,10 +4,10 @@
#include <linux/proc_fs.h> /* for struct inode and struct file */
#include <linux/tracepoint.h>

-DEFINE_TRACE(subsys_event,
+DECLARE_TRACE(subsys_event,
TPPROTO(struct inode *inode, struct file *file),
TPARGS(inode, file));
-DEFINE_TRACE(subsys_eventb,
+DECLARE_TRACE(subsys_eventb,
TPPROTO(void),
TPARGS());
#endif
Index: linux.trees.git/include/asm-generic/vmlinux.lds.h
===================================================================
--- linux.trees.git.orig/include/asm-generic/vmlinux.lds.h 2008-11-14 17:38:29.000000000 -0500
+++ linux.trees.git/include/asm-generic/vmlinux.lds.h 2008-11-14 17:40:54.000000000 -0500
@@ -71,6 +71,7 @@
VMLINUX_SYMBOL(__start___markers) = .; \
*(__markers) \
VMLINUX_SYMBOL(__stop___markers) = .; \
+ . = ALIGN(32); \
VMLINUX_SYMBOL(__start___tracepoints) = .; \
*(__tracepoints) \
VMLINUX_SYMBOL(__stop___tracepoints) = .; \
Index: linux.trees.git/include/trace/sched.h
===================================================================
--- linux.trees.git.orig/include/trace/sched.h 2008-11-14 17:37:14.000000000 -0500
+++ linux.trees.git/include/trace/sched.h 2008-11-14 17:40:54.000000000 -0500
@@ -4,52 +4,52 @@
#include <linux/sched.h>
#include <linux/tracepoint.h>

-DEFINE_TRACE(sched_kthread_stop,
+DECLARE_TRACE(sched_kthread_stop,
TPPROTO(struct task_struct *t),
TPARGS(t));

-DEFINE_TRACE(sched_kthread_stop_ret,
+DECLARE_TRACE(sched_kthread_stop_ret,
TPPROTO(int ret),
TPARGS(ret));

-DEFINE_TRACE(sched_wait_task,
+DECLARE_TRACE(sched_wait_task,
TPPROTO(struct rq *rq, struct task_struct *p),
TPARGS(rq, p));

-DEFINE_TRACE(sched_wakeup,
+DECLARE_TRACE(sched_wakeup,
TPPROTO(struct rq *rq, struct task_struct *p),
TPARGS(rq, p));

-DEFINE_TRACE(sched_wakeup_new,
+DECLARE_TRACE(sched_wakeup_new,
TPPROTO(struct rq *rq, struct task_struct *p),
TPARGS(rq, p));

-DEFINE_TRACE(sched_switch,
+DECLARE_TRACE(sched_switch,
TPPROTO(struct rq *rq, struct task_struct *prev,
struct task_struct *next),
TPARGS(rq, prev, next));

-DEFINE_TRACE(sched_migrate_task,
+DECLARE_TRACE(sched_migrate_task,
TPPROTO(struct rq *rq, struct task_struct *p, int dest_cpu),
TPARGS(rq, p, dest_cpu));

-DEFINE_TRACE(sched_process_free,
+DECLARE_TRACE(sched_process_free,
TPPROTO(struct task_struct *p),
TPARGS(p));

-DEFINE_TRACE(sched_process_exit,
+DECLARE_TRACE(sched_process_exit,
TPPROTO(struct task_struct *p),
TPARGS(p));

-DEFINE_TRACE(sched_process_wait,
+DECLARE_TRACE(sched_process_wait,
TPPROTO(struct pid *pid),
TPARGS(pid));

-DEFINE_TRACE(sched_process_fork,
+DECLARE_TRACE(sched_process_fork,
TPPROTO(struct task_struct *parent, struct task_struct *child),
TPARGS(parent, child));

-DEFINE_TRACE(sched_signal_send,
+DECLARE_TRACE(sched_signal_send,
TPPROTO(int sig, struct task_struct *p),
TPARGS(sig, p));

Index: linux.trees.git/kernel/sched.c
===================================================================
--- linux.trees.git.orig/kernel/sched.c 2008-11-14 17:38:29.000000000 -0500
+++ linux.trees.git/kernel/sched.c 2008-11-14 17:40:54.000000000 -0500
@@ -118,6 +118,12 @@
*/
#define RUNTIME_INF ((u64)~0ULL)

+DEFINE_TRACE(sched_wait_task);
+DEFINE_TRACE(sched_wakeup);
+DEFINE_TRACE(sched_wakeup_new);
+DEFINE_TRACE(sched_switch);
+DEFINE_TRACE(sched_migrate_task);
+
#ifdef CONFIG_SMP
/*
* Divide a load by a sched group cpu_power : (load / sg->__cpu_power)
Index: linux.trees.git/kernel/exit.c
===================================================================
--- linux.trees.git.orig/kernel/exit.c 2008-11-14 17:38:29.000000000 -0500
+++ linux.trees.git/kernel/exit.c 2008-11-14 17:40:54.000000000 -0500
@@ -54,6 +54,10 @@
#include <asm/pgtable.h>
#include <asm/mmu_context.h>

+DEFINE_TRACE(sched_process_free);
+DEFINE_TRACE(sched_process_exit);
+DEFINE_TRACE(sched_process_wait);
+
static void exit_mm(struct task_struct * tsk);

static inline int task_detached(struct task_struct *p)
Index: linux.trees.git/kernel/fork.c
===================================================================
--- linux.trees.git.orig/kernel/fork.c 2008-11-14 17:38:29.000000000 -0500
+++ linux.trees.git/kernel/fork.c 2008-11-14 17:40:54.000000000 -0500
@@ -80,6 +80,8 @@ DEFINE_PER_CPU(unsigned long, process_co

__cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */

+DEFINE_TRACE(sched_process_fork);
+
int nr_processes(void)
{
int cpu;
Index: linux.trees.git/kernel/kthread.c
===================================================================
--- linux.trees.git.orig/kernel/kthread.c 2008-11-14 17:37:14.000000000 -0500
+++ linux.trees.git/kernel/kthread.c 2008-11-14 17:40:54.000000000 -0500
@@ -21,6 +21,9 @@ static DEFINE_SPINLOCK(kthread_create_lo
static LIST_HEAD(kthread_create_list);
struct task_struct *kthreadd_task;

+DEFINE_TRACE(sched_kthread_stop);
+DEFINE_TRACE(sched_kthread_stop_ret);
+
struct kthread_create_info
{
/* Information passed to kthread() from kthreadd. */
Index: linux.trees.git/kernel/signal.c
===================================================================
--- linux.trees.git.orig/kernel/signal.c 2008-11-14 17:37:13.000000000 -0500
+++ linux.trees.git/kernel/signal.c 2008-11-14 17:40:54.000000000 -0500
@@ -41,6 +41,8 @@

static struct kmem_cache *sigqueue_cachep;

+DEFINE_TRACE(sched_signal_send);
+
static void __user *sig_handler(struct task_struct *t, int sig)
{
return t->sighand->action[sig - 1].sa.sa_handler;
--
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68


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