Commit a9cfb877 authored by Mathieu Desnoyers's avatar Mathieu Desnoyers Committed by Steven Rostedt (Google)
Browse files

tracing: Introduce tracepoint extended structure 



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: default avatarJordan 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: default avatarMathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: default avatarSteven Rostedt (Google) <rostedt@goodmis.org>
parent e9f0a363

include/linux/tracepoint-defs.h

+6 −2
Original line number Diff line number Diff line
@@ -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

include/linux/tracepoint.h

+13 −6
Original line number Diff line number Diff line
@@ -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);				\

kernel/tracepoint.c

+4 −5
Original line number Diff line number Diff line
@@ -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);