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: 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>

diff --git a/include/linux/tracepoint-defs.h b/include/linux/tracepoint-defs.h
index 60a6e8314d4cc33b8453104d53d4e4cda939aefc..967c08d9da848b626ff2785a643744d234b87271 100644 (file)
--- 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 0dc67fad706c6bfa2b7e39443bf53366934e1c8e..862ab49177a44e1b8596bdaf3c28e0ad46e1acd0 100644 (file)
--- 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 6474e2cf22c965a64f1ed55a2e4f292c34994efc..5658dc92f5b589caa562e3c263af5548d0c8b2fb 100644 (file)
--- 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);