[for-next][PATCH 07/11] tracing: Introduce tracepoint extended structure

Steven Rostedt
2024-11-01T10:36:09Z

From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>

Shrink the struct tracepoint size from 80 bytes to 72 bytes on x86-64 by
moving the (typically NULL) regfunc/unregfunc pointers to an extended
structure.

Tested-by: Jordan Rife <jrife@google.com>
Cc: Michael Jeanson <mjeanson@efficios.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Yonghong Song <yhs@fb.com>
Cc: Paul E. McKenney <paulmck@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc: bpf@vger.kernel.org
Cc: Joel Fernandes <joel@joelfernandes.org>
Cc: Jordan Rife <jrife@google.com>
Cc: linux-trace-kernel@vger.kernel.org
Link: https://lore.kernel.org/20241031152056.744137-2-mathieu.desnoyers@efficios.com
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
include/linux/tracepoint-defs.h | 8 ++++++--
include/linux/tracepoint.h | 19 +++++++++++++------
kernel/tracepoint.c | 9 ++++-----
3 files changed, 23 insertions(+), 13 deletions(-)

diff --git a/include/linux/tracepoint-defs.h b/include/linux/tracepoint-defs.h
index 60a6e8314d4c..967c08d9da84 100644
--- a/include/linux/tracepoint-defs.h
+++ b/include/linux/tracepoint-defs.h
@@ -29,6 +29,11 @@ struct tracepoint_func {
int prio;
};

+struct tracepoint_ext {
+ int (*regfunc)(void);
+ void (*unregfunc)(void);
+};
+
struct tracepoint {
const char *name; /* Tracepoint name */
struct static_key_false key;
@@ -36,9 +41,8 @@ struct tracepoint {
void *static_call_tramp;
void *iterator;
void *probestub;
- int (*regfunc)(void);
- void (*unregfunc)(void);
struct tracepoint_func __rcu *funcs;
+ struct tracepoint_ext *ext;
};

#ifdef CONFIG_HAVE_ARCH_PREL32_RELOCATIONS
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 0dc67fad706c..862ab49177a4 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -302,7 +302,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
* structures, so we create an array of pointers that will be used for iteration
* on the tracepoints.
*/
-#define DEFINE_TRACE_FN(_name, _reg, _unreg, proto, args) \
+#define __DEFINE_TRACE_EXT(_name, _ext, proto, args) \
static const char __tpstrtab_##_name[] \
__section("__tracepoints_strings") = #_name; \
extern struct static_call_key STATIC_CALL_KEY(tp_func_##_name); \
@@ -316,9 +316,9 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
.static_call_tramp = STATIC_CALL_TRAMP_ADDR(tp_func_##_name), \
.iterator = &__traceiter_##_name, \
.probestub = &__probestub_##_name, \
- .regfunc = _reg, \
- .unregfunc = _unreg, \
- .funcs = NULL }; \
+ .funcs = NULL, \
+ .ext = _ext, \
+ }; \
__TRACEPOINT_ENTRY(_name); \
int __traceiter_##_name(void *__data, proto) \
{ \
@@ -341,8 +341,15 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
} \
DEFINE_STATIC_CALL(tp_func_##_name, __traceiter_##_name);

-#define DEFINE_TRACE(name, proto, args) \
- DEFINE_TRACE_FN(name, NULL, NULL, PARAMS(proto), PARAMS(args));
+#define DEFINE_TRACE_FN(_name, _reg, _unreg, _proto, _args) \
+ static struct tracepoint_ext __tracepoint_ext_##_name = { \
+ .regfunc = _reg, \
+ .unregfunc = _unreg, \
+ }; \
+ __DEFINE_TRACE_EXT(_name, &__tracepoint_ext_##_name, PARAMS(_proto), PARAMS(_args));
+
+#define DEFINE_TRACE(_name, _proto, _args) \
+ __DEFINE_TRACE_EXT(_name, NULL, PARAMS(_proto), PARAMS(_args));

#define EXPORT_TRACEPOINT_SYMBOL_GPL(name) \
EXPORT_SYMBOL_GPL(__tracepoint_##name); \
diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index 6474e2cf22c9..5658dc92f5b5 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -278,8 +278,8 @@ static int tracepoint_add_func(struct tracepoint *tp,
struct tracepoint_func *old, *tp_funcs;
int ret;

- if (tp->regfunc && !static_key_enabled(&tp->key)) {
- ret = tp->regfunc();
+ if (tp->ext && tp->ext->regfunc && !static_key_enabled(&tp->key)) {
+ ret = tp->ext->regfunc();
if (ret < 0)
return ret;
}
@@ -362,9 +362,8 @@ static int tracepoint_remove_func(struct tracepoint *tp,
switch (nr_func_state(tp_funcs)) {
case TP_FUNC_0: /* 1->0 */
/* Removed last function */
- if (tp->unregfunc && static_key_enabled(&tp->key))
- tp->unregfunc();
-
+ if (tp->ext && tp->ext->unregfunc && static_key_enabled(&tp->key))
+ tp->ext->unregfunc();
static_branch_disable(&tp->key);
/* Set iterator static call */
tracepoint_update_call(tp, tp_funcs);
--
2.45.2