Messages in this thread Patch in this message | | | Date | Tue, 19 May 2009 17:03:39 -0400 | From | Jason Baron <> | Subject | [PATCH 1/3] tracepoints: add tracepoint_call() to optimize tracepoints disabled |
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Add a wrapper function call before the call to 'trace_##name'. This preserves the type checking, while allowing arguments that are passed to the tracepoint to not be evaluated until after the tracepoint on/off check is performed. This reduces the cost when tracepoints are disabled.
Signed-off-by: Jason Baron <jbaron@redhat.com>
--- include/linux/tracepoint.h | 20 +++++++++++++++++++- 1 files changed, 19 insertions(+), 1 deletions(-)
diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h index 14df7e6..d747c78 100644 --- a/include/linux/tracepoint.h +++ b/include/linux/tracepoint.h @@ -65,7 +65,6 @@ struct tracepoint { extern struct tracepoint __tracepoint_##name; \ static inline void trace_##name(proto) \ { \ - if (unlikely(__tracepoint_##name.state)) \ __DO_TRACE(&__tracepoint_##name, \ TP_PROTO(proto), TP_ARGS(args)); \ } \ @@ -78,6 +77,19 @@ struct tracepoint { return tracepoint_probe_unregister(#name, (void *)probe);\ } +/* + * Use this function in the instrumented code. This wrapper call to trace_##name + * is added so that arguments aren't evaluated, and do not have side-effects + * when a tracepoint is disabled. We still call the inline for type checking. + */ + +#define tracepoint_call(name, ...) \ +do { \ + extern struct tracepoint __tracepoint_##name;\ + if (unlikely(__tracepoint_##name.state)) \ + trace_##name(__VA_ARGS__); \ +} while (0) + #define DEFINE_TRACE(name) \ static const char __tpstrtab_##name[] \ __attribute__((section("__tracepoints_strings"))) = #name; \ @@ -108,6 +120,12 @@ extern void tracepoint_update_probe_range(struct tracepoint *begin, return -ENOSYS; \ } +#define tracepoint_call(name, ...) \ +do { \ + if (0) \ + trace_##name(__VA_ARGS__);\ +} while (0) + #define DEFINE_TRACE(name) #define EXPORT_TRACEPOINT_SYMBOL_GPL(name) #define EXPORT_TRACEPOINT_SYMBOL(name) -- 1.6.0.6
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