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authorSteven Rostedt (VMware)2020-08-18 15:57:52 +0200
committerIngo Molnar2020-09-01 09:58:06 +0200
commitd25e37d89dd2f41d7acae0429039d2f0ae8b4a07 (patch)
tree16e6d52b374b3907e51dd3a96b30f3c427f9a55f /include/linux/tracepoint.h
parenta945c8345ec0decb2f1a7f19a8c5e60bcb1dd1eb (diff)
tracepoint: Optimize using static_call()
Currently the tracepoint site will iterate a vector and issue indirect calls to however many handlers are registered (ie. the vector is long). Using static_call() it is possible to optimize this for the common case of only having a single handler registered. In this case the static_call() can directly call this handler. Otherwise, if the vector is longer than 1, call a function that iterates the whole vector like the current code. [peterz: updated to new interface] Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Link: https://lore.kernel.org/r/20200818135805.279421092@infradead.org
Diffstat (limited to 'include/linux/tracepoint.h')
-rw-r--r--include/linux/tracepoint.h86
1 files changed, 61 insertions, 25 deletions
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 598fec9f9dbf..3722a10fc46d 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -19,6 +19,7 @@
#include <linux/cpumask.h>
#include <linux/rcupdate.h>
#include <linux/tracepoint-defs.h>
+#include <linux/static_call.h>
struct module;
struct tracepoint;
@@ -92,7 +93,9 @@ extern int syscall_regfunc(void);
extern void syscall_unregfunc(void);
#endif /* CONFIG_HAVE_SYSCALL_TRACEPOINTS */
+#ifndef PARAMS
#define PARAMS(args...) args
+#endif
#define TRACE_DEFINE_ENUM(x)
#define TRACE_DEFINE_SIZEOF(x)
@@ -148,6 +151,12 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
#ifdef TRACEPOINTS_ENABLED
+#ifdef CONFIG_HAVE_STATIC_CALL
+#define __DO_TRACE_CALL(name) static_call(tp_func_##name)
+#else
+#define __DO_TRACE_CALL(name) __tracepoint_iter_##name
+#endif /* CONFIG_HAVE_STATIC_CALL */
+
/*
* it_func[0] is never NULL because there is at least one element in the array
* when the array itself is non NULL.
@@ -157,12 +166,11 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
* has a "void" prototype, then it is invalid to declare a function
* as "(void *, void)".
*/
-#define __DO_TRACE(tp, proto, args, cond, rcuidle) \
+#define __DO_TRACE(name, proto, args, cond, rcuidle) \
do { \
struct tracepoint_func *it_func_ptr; \
- void *it_func; \
- void *__data; \
int __maybe_unused __idx = 0; \
+ void *__data; \
\
if (!(cond)) \
return; \
@@ -182,14 +190,11 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
rcu_irq_enter_irqson(); \
} \
\
- it_func_ptr = rcu_dereference_raw((tp)->funcs); \
- \
+ it_func_ptr = \
+ rcu_dereference_raw((&__tracepoint_##name)->funcs); \
if (it_func_ptr) { \
- do { \
- it_func = (it_func_ptr)->func; \
- __data = (it_func_ptr)->data; \
- ((void(*)(proto))(it_func))(args); \
- } while ((++it_func_ptr)->func); \
+ __data = (it_func_ptr)->data; \
+ __DO_TRACE_CALL(name)(args); \
} \
\
if (rcuidle) { \
@@ -205,7 +210,7 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
static inline void trace_##name##_rcuidle(proto) \
{ \
if (static_key_false(&__tracepoint_##name.key)) \
- __DO_TRACE(&__tracepoint_##name, \
+ __DO_TRACE(name, \
TP_PROTO(data_proto), \
TP_ARGS(data_args), \
TP_CONDITION(cond), 1); \
@@ -227,11 +232,13 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
* poking RCU a bit.
*/
#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
+ extern int __tracepoint_iter_##name(data_proto); \
+ DECLARE_STATIC_CALL(tp_func_##name, __tracepoint_iter_##name); \
extern struct tracepoint __tracepoint_##name; \
static inline void trace_##name(proto) \
{ \
if (static_key_false(&__tracepoint_##name.key)) \
- __DO_TRACE(&__tracepoint_##name, \
+ __DO_TRACE(name, \
TP_PROTO(data_proto), \
TP_ARGS(data_args), \
TP_CONDITION(cond), 0); \
@@ -277,21 +284,50 @@ 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) \
- static const char __tpstrtab_##name[] \
- __section(__tracepoints_strings) = #name; \
- struct tracepoint __tracepoint_##name __used \
- __section(__tracepoints) = \
- { __tpstrtab_##name, STATIC_KEY_INIT_FALSE, reg, unreg, NULL };\
- __TRACEPOINT_ENTRY(name);
+#define DEFINE_TRACE_FN(_name, _reg, _unreg, proto, args) \
+ static const char __tpstrtab_##_name[] \
+ __section(__tracepoints_strings) = #_name; \
+ extern struct static_call_key STATIC_CALL_KEY(tp_func_##_name); \
+ int __tracepoint_iter_##_name(void *__data, proto); \
+ struct tracepoint __tracepoint_##_name __used \
+ __section(__tracepoints) = { \
+ .name = __tpstrtab_##_name, \
+ .key = STATIC_KEY_INIT_FALSE, \
+ .static_call_key = &STATIC_CALL_KEY(tp_func_##_name), \
+ .static_call_tramp = STATIC_CALL_TRAMP_ADDR(tp_func_##_name), \
+ .iterator = &__tracepoint_iter_##_name, \
+ .regfunc = _reg, \
+ .unregfunc = _unreg, \
+ .funcs = NULL }; \
+ __TRACEPOINT_ENTRY(_name); \
+ int __tracepoint_iter_##_name(void *__data, proto) \
+ { \
+ struct tracepoint_func *it_func_ptr; \
+ void *it_func; \
+ \
+ it_func_ptr = \
+ rcu_dereference_raw((&__tracepoint_##_name)->funcs); \
+ do { \
+ it_func = (it_func_ptr)->func; \
+ __data = (it_func_ptr)->data; \
+ ((void(*)(void *, proto))(it_func))(__data, args); \
+ } while ((++it_func_ptr)->func); \
+ return 0; \
+ } \
+ DEFINE_STATIC_CALL(tp_func_##_name, __tracepoint_iter_##_name);
-#define DEFINE_TRACE(name) \
- DEFINE_TRACE_FN(name, NULL, NULL);
+#define DEFINE_TRACE(name, proto, args) \
+ DEFINE_TRACE_FN(name, NULL, NULL, PARAMS(proto), PARAMS(args));
#define EXPORT_TRACEPOINT_SYMBOL_GPL(name) \
- EXPORT_SYMBOL_GPL(__tracepoint_##name)
+ EXPORT_SYMBOL_GPL(__tracepoint_##name); \
+ EXPORT_SYMBOL_GPL(__tracepoint_iter_##name); \
+ EXPORT_STATIC_CALL_GPL(tp_func_##name)
#define EXPORT_TRACEPOINT_SYMBOL(name) \
- EXPORT_SYMBOL(__tracepoint_##name)
+ EXPORT_SYMBOL(__tracepoint_##name); \
+ EXPORT_SYMBOL(__tracepoint_iter_##name); \
+ EXPORT_STATIC_CALL(tp_func_##name)
+
#else /* !TRACEPOINTS_ENABLED */
#define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
@@ -320,8 +356,8 @@ static inline struct tracepoint *tracepoint_ptr_deref(tracepoint_ptr_t *p)
return false; \
}
-#define DEFINE_TRACE_FN(name, reg, unreg)
-#define DEFINE_TRACE(name)
+#define DEFINE_TRACE_FN(name, reg, unreg, proto, args)
+#define DEFINE_TRACE(name, proto, args)
#define EXPORT_TRACEPOINT_SYMBOL_GPL(name)
#define EXPORT_TRACEPOINT_SYMBOL(name)