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authorJason Baron <jbaron@redhat.com>2011-03-16 17:29:47 -0400
committerSteven Rostedt <rostedt@goodmis.org>2011-04-04 12:48:08 -0400
commitd430d3d7e646eb1eac2bb4aa244a644312e67c76 (patch)
tree0f52534f54d89e41042536ff2f1b2ce74c45c033 /include/linux/tracepoint.h
parentee5e51f51be755830f57445e268ba50e88ccbdbb (diff)
jump label: Introduce static_branch() interface
Introduce: static __always_inline bool static_branch(struct jump_label_key *key); instead of the old JUMP_LABEL(key, label) macro. In this way, jump labels become really easy to use: Define: struct jump_label_key jump_key; Can be used as: if (static_branch(&jump_key)) do unlikely code enable/disale via: jump_label_inc(&jump_key); jump_label_dec(&jump_key); that's it! For the jump labels disabled case, the static_branch() becomes an atomic_read(), and jump_label_inc()/dec() are simply atomic_inc(), atomic_dec() operations. We show testing results for this change below. Thanks to H. Peter Anvin for suggesting the 'static_branch()' construct. Since we now require a 'struct jump_label_key *key', we can store a pointer into the jump table addresses. In this way, we can enable/disable jump labels, in basically constant time. This change allows us to completely remove the previous hashtable scheme. Thanks to Peter Zijlstra for this re-write. Testing: I ran a series of 'tbench 20' runs 5 times (with reboots) for 3 configurations, where tracepoints were disabled. jump label configured in avg: 815.6 jump label *not* configured in (using atomic reads) avg: 800.1 jump label *not* configured in (regular reads) avg: 803.4 Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <20110316212947.GA8792@redhat.com> Signed-off-by: Jason Baron <jbaron@redhat.com> Suggested-by: H. Peter Anvin <hpa@linux.intel.com> Tested-by: David Daney <ddaney@caviumnetworks.com> Acked-by: Ralf Baechle <ralf@linux-mips.org> Acked-by: David S. Miller <davem@davemloft.net> Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'include/linux/tracepoint.h')
-rw-r--r--include/linux/tracepoint.h22
1 files changed, 10 insertions, 12 deletions
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
index 97c84a58efb8..d530a4460a0b 100644
--- a/include/linux/tracepoint.h
+++ b/include/linux/tracepoint.h
@@ -29,7 +29,7 @@ struct tracepoint_func {
29 29
30struct tracepoint { 30struct tracepoint {
31 const char *name; /* Tracepoint name */ 31 const char *name; /* Tracepoint name */
32 int state; /* State. */ 32 struct jump_label_key key;
33 void (*regfunc)(void); 33 void (*regfunc)(void);
34 void (*unregfunc)(void); 34 void (*unregfunc)(void);
35 struct tracepoint_func __rcu *funcs; 35 struct tracepoint_func __rcu *funcs;
@@ -146,9 +146,7 @@ void tracepoint_update_probe_range(struct tracepoint * const *begin,
146 extern struct tracepoint __tracepoint_##name; \ 146 extern struct tracepoint __tracepoint_##name; \
147 static inline void trace_##name(proto) \ 147 static inline void trace_##name(proto) \
148 { \ 148 { \
149 JUMP_LABEL(&__tracepoint_##name.state, do_trace); \ 149 if (static_branch(&__tracepoint_##name.key)) \
150 return; \
151do_trace: \
152 __DO_TRACE(&__tracepoint_##name, \ 150 __DO_TRACE(&__tracepoint_##name, \
153 TP_PROTO(data_proto), \ 151 TP_PROTO(data_proto), \
154 TP_ARGS(data_args), \ 152 TP_ARGS(data_args), \
@@ -176,14 +174,14 @@ do_trace: \
176 * structures, so we create an array of pointers that will be used for iteration 174 * structures, so we create an array of pointers that will be used for iteration
177 * on the tracepoints. 175 * on the tracepoints.
178 */ 176 */
179#define DEFINE_TRACE_FN(name, reg, unreg) \ 177#define DEFINE_TRACE_FN(name, reg, unreg) \
180 static const char __tpstrtab_##name[] \ 178 static const char __tpstrtab_##name[] \
181 __attribute__((section("__tracepoints_strings"))) = #name; \ 179 __attribute__((section("__tracepoints_strings"))) = #name; \
182 struct tracepoint __tracepoint_##name \ 180 struct tracepoint __tracepoint_##name \
183 __attribute__((section("__tracepoints"))) = \ 181 __attribute__((section("__tracepoints"))) = \
184 { __tpstrtab_##name, 0, reg, unreg, NULL }; \ 182 { __tpstrtab_##name, JUMP_LABEL_INIT, reg, unreg, NULL };\
185 static struct tracepoint * const __tracepoint_ptr_##name __used \ 183 static struct tracepoint * const __tracepoint_ptr_##name __used \
186 __attribute__((section("__tracepoints_ptrs"))) = \ 184 __attribute__((section("__tracepoints_ptrs"))) = \
187 &__tracepoint_##name; 185 &__tracepoint_##name;
188 186
189#define DEFINE_TRACE(name) \ 187#define DEFINE_TRACE(name) \