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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
This commit is contained in:
Steven Rostedt (VMware) 2020-08-18 15:57:52 +02:00 committed by Ingo Molnar
parent a945c8345e
commit d25e37d89d
4 changed files with 94 additions and 36 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
include/linux/tracepoint-defs.h
View File

@ -11,6 +11,8 @@
#include <linux/atomic.h>
#include <linux/static_key.h>
struct static_call_key;
struct trace_print_flags {
unsigned long mask;
const char *name;
@ -30,6 +32,9 @@ struct tracepoint_func {
struct tracepoint {
const char *name; /* Tracepoint name */
struct static_key key;
struct static_call_key *static_call_key;
void *static_call_tramp;
void *iterator;
int (*regfunc)(void);
void (*unregfunc)(void);
struct tracepoint_func __rcu *funcs;

86
include/linux/tracepoint.h
View File

@ -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)

14
include/trace/define_trace.h
View File

@ -25,7 +25,7 @@
#undef TRACE_EVENT
#define TRACE_EVENT(name, proto, args, tstruct, assign, print) \
DEFINE_TRACE(name)
DEFINE_TRACE(name, PARAMS(proto), PARAMS(args))
#undef TRACE_EVENT_CONDITION
#define TRACE_EVENT_CONDITION(name, proto, args, cond, tstruct, assign, print) \
@ -39,12 +39,12 @@
#undef TRACE_EVENT_FN
#define TRACE_EVENT_FN(name, proto, args, tstruct, \
assign, print, reg, unreg) \
DEFINE_TRACE_FN(name, reg, unreg)
DEFINE_TRACE_FN(name, reg, unreg, PARAMS(proto), PARAMS(args))
#undef TRACE_EVENT_FN_COND
#define TRACE_EVENT_FN_COND(name, proto, args, cond, tstruct, \
assign, print, reg, unreg) \
DEFINE_TRACE_FN(name, reg, unreg)
DEFINE_TRACE_FN(name, reg, unreg, PARAMS(proto), PARAMS(args))
#undef TRACE_EVENT_NOP
#define TRACE_EVENT_NOP(name, proto, args, struct, assign, print)
@ -54,15 +54,15 @@
#undef DEFINE_EVENT
#define DEFINE_EVENT(template, name, proto, args) \
DEFINE_TRACE(name)
DEFINE_TRACE(name, PARAMS(proto), PARAMS(args))
#undef DEFINE_EVENT_FN
#define DEFINE_EVENT_FN(template, name, proto, args, reg, unreg) \
DEFINE_TRACE_FN(name, reg, unreg)
DEFINE_TRACE_FN(name, reg, unreg, PARAMS(proto), PARAMS(args))
#undef DEFINE_EVENT_PRINT
#define DEFINE_EVENT_PRINT(template, name, proto, args, print) \
DEFINE_TRACE(name)
DEFINE_TRACE(name, PARAMS(proto), PARAMS(args))
#undef DEFINE_EVENT_CONDITION
#define DEFINE_EVENT_CONDITION(template, name, proto, args, cond) \
@ -70,7 +70,7 @@
#undef DECLARE_TRACE
#define DECLARE_TRACE(name, proto, args) \
DEFINE_TRACE(name)
DEFINE_TRACE(name, PARAMS(proto), PARAMS(args))
#undef TRACE_INCLUDE
#undef __TRACE_INCLUDE

25
kernel/tracepoint.c
View File

@ -221,6 +221,20 @@ static void *func_remove(struct tracepoint_func **funcs,
return old;
}
static void tracepoint_update_call(struct tracepoint *tp, struct tracepoint_func *tp_funcs)
{
void *func = tp->iterator;
/* Synthetic events do not have static call sites */
if (!tp->static_call_key)
return;
if (!tp_funcs[1].func)
func = tp_funcs[0].func;
__static_call_update(tp->static_call_key, tp->static_call_tramp, func);
}
/*
* Add the probe function to a tracepoint.
*/
@ -251,8 +265,9 @@ static int tracepoint_add_func(struct tracepoint *tp,
* include/linux/tracepoint.h using rcu_dereference_sched().
*/
rcu_assign_pointer(tp->funcs, tp_funcs);
if (!static_key_enabled(&tp->key))
static_key_slow_inc(&tp->key);
tracepoint_update_call(tp, tp_funcs);
static_key_enable(&tp->key);
release_probes(old);
return 0;
}
@ -281,9 +296,11 @@ static int tracepoint_remove_func(struct tracepoint *tp,
if (tp->unregfunc && static_key_enabled(&tp->key))
tp->unregfunc();
if (static_key_enabled(&tp->key))
static_key_slow_dec(&tp->key);
static_key_disable(&tp->key);
} else {
tracepoint_update_call(tp, tp_funcs);
}
rcu_assign_pointer(tp->funcs, tp_funcs);
release_probes(old);
return 0;