trace.h: support nested performance tracing

Performance measurements are listed right now as a flat list, which is
fine when we measure big blocks. But when we start adding more and
more measurements, some of them could be just part of a bigger
measurement and a flat list gives a wrong impression that they are
executed at the same level instead of nested.

Add trace_performance_enter() and trace_performance_leave() to allow
indent these nested measurements. For now it does not help much
because the only nested thing is (lazy) name hash initialization
(e.g. called in diff-index from "git status"). This will help more
because I'm going to add some more tracing that's actually nested.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/trace.h b/trace.h
index 2b6a1bc17c..171b256d26 100644
--- a/trace.h
+++ b/trace.h
@@ -23,6 +23,7 @@ extern void trace_disable(struct trace_key *key);
 extern uint64_t getnanotime(void);
 extern void trace_command_performance(const char **argv);
 extern void trace_verbatim(struct trace_key *key, const void *buf, unsigned len);
+uint64_t trace_performance_enter(void);
 
 #ifndef HAVE_VARIADIC_MACROS
 
@@ -45,6 +46,9 @@ extern void trace_performance(uint64_t nanos, const char *format, ...);
 __attribute__((format (printf, 2, 3)))
 extern void trace_performance_since(uint64_t start, const char *format, ...);
 
+__attribute__((format (printf, 1, 2)))
+void trace_performance_leave(const char *format, ...);
+
 #else
 
 /*
@@ -118,6 +122,14 @@ extern void trace_performance_since(uint64_t start, const char *format, ...);
 					     __VA_ARGS__);		    \
 	} while (0)
 
+#define trace_performance_leave(...)					    \
+	do {								    \
+		if (trace_pass_fl(&trace_perf_key))			    \
+			trace_performance_leave_fl(TRACE_CONTEXT, __LINE__, \
+						   getnanotime(),	    \
+						   __VA_ARGS__);	    \
+	} while (0)
+
 /* backend functions, use non-*fl macros instead */
 __attribute__((format (printf, 4, 5)))
 extern void trace_printf_key_fl(const char *file, int line, struct trace_key *key,
@@ -130,6 +142,9 @@ extern void trace_strbuf_fl(const char *file, int line, struct trace_key *key,
 __attribute__((format (printf, 4, 5)))
 extern void trace_performance_fl(const char *file, int line,
 				 uint64_t nanos, const char *fmt, ...);
+__attribute__((format (printf, 4, 5)))
+extern void trace_performance_leave_fl(const char *file, int line,
+				       uint64_t nanos, const char *fmt, ...);
 static inline int trace_pass_fl(struct trace_key *key)
 {
 	return key->fd || !key->initialized;