[PATCH 2/2] Reduce performance cost of the trace if trace category is disabled

[gennady.kupava@xxxxxxxxx]

From: Gennady Kupava <gkupava@xxxxxxxxxxxxx>

- Do the check if the trace key is enabled sooner in call chain.
- Move just enough code from trace.c into trace.h header so all code
  necessary to determine that trace is disabled could be inlined to
  calling functions.

Signed-off-by: Gennady Kupava <gkupava@xxxxxxxxxxxxx>
---
 trace.c |  3 +--
 trace.h | 58 ++++++++++++++++++++++++++++++++++++++++------------------
 2 files changed, 41 insertions(+), 20 deletions(-)

diff --git a/trace.c b/trace.c
index d47ea28e8..b7530b51a 100644
--- a/trace.c
+++ b/trace.c
@@ -25,6 +25,7 @@
 #include "quote.h"
 
 struct trace_key trace_default_key = { "GIT_TRACE", 0, 0, 0 };
+struct trace_key trace_perf_key = TRACE_KEY_INIT(PERFORMANCE);
 
 /* Get a trace file descriptor from "key" env variable. */
 static int get_trace_fd(struct trace_key *key)
@@ -172,8 +173,6 @@ void trace_strbuf_fl(const char *file, int line, struct trace_key *key,
 	print_trace_line(key, &buf);
 }
 
-static struct trace_key trace_perf_key = TRACE_KEY_INIT(PERFORMANCE);
-
 static void trace_performance_vprintf_fl(const char *file, int line,
 					 uint64_t nanos, const char *format,
 					 va_list ap)
diff --git a/trace.h b/trace.h
index 24b32f8f4..cd9e280ba 100644
--- a/trace.h
+++ b/trace.h
@@ -14,6 +14,7 @@ struct trace_key {
 extern struct trace_key trace_default_key;
 
 #define TRACE_KEY_INIT(name) { "GIT_TRACE_" #name, 0, 0, 0 }
+extern struct trace_key trace_perf_key;
 
 extern void trace_repo_setup(const char *prefix);
 extern int trace_want(struct trace_key *key);
@@ -79,24 +80,42 @@ extern void trace_performance_since(uint64_t start, const char *format, ...);
  * comma, but this is non-standard.
  */
 
-#define trace_printf(...) \
-	trace_printf_key_fl(TRACE_CONTEXT, __LINE__, &trace_default_key, __VA_ARGS__)
-
-#define trace_printf_key(key, ...) \
-	trace_printf_key_fl(TRACE_CONTEXT, __LINE__, key, __VA_ARGS__)
-
-#define trace_argv_printf(argv, ...) \
-	trace_argv_printf_fl(TRACE_CONTEXT, __LINE__, argv, __VA_ARGS__)
-
-#define trace_strbuf(key, data) \
-	trace_strbuf_fl(TRACE_CONTEXT, __LINE__, key, data)
-
-#define trace_performance(nanos, ...) \
-	trace_performance_fl(TRACE_CONTEXT, __LINE__, nanos, __VA_ARGS__)
-
-#define trace_performance_since(start, ...) \
-	trace_performance_fl(TRACE_CONTEXT, __LINE__, getnanotime() - (start), \
-			     __VA_ARGS__)
+#define trace_printf_key(key, ...)					    \
+	do {								    \
+		if (trace_pass_fl(key))					    \
+			trace_printf_key_fl(TRACE_CONTEXT, __LINE__, key,   \
+					    __VA_ARGS__);		    \
+	} while(0)
+
+#define trace_printf(...) trace_printf_key(&trace_default_key, __VA_ARGS__);
+
+#define trace_argv_printf(argv, ...)					    \
+	do {								    \
+		if (trace_pass_fl(&trace_default_key))			    \
+		       trace_argv_printf_fl(TRACE_CONTEXT, __LINE__,	    \
+					    argv, __VA_ARGS__);		    \
+	} while(0)
+
+#define trace_strbuf(key, data)						    \
+	do {								    \
+		if (trace_pass_fl(key))					    \
+			trace_strbuf_fl(TRACE_CONTEXT, __LINE__, key, data);\
+	} while(0)
+
+#define trace_performance(nanos, ...)					    \
+	do {								    \
+		if (trace_pass_fl(key))					    \
+			trace_performance_fl(TRACE_CONTEXT, __LINE__, nanos,\
+					     __VA_ARGS__);  		    \
+	} while(0)
+
+#define trace_performance_since(start, ...)				    \
+	do {								    \
+		if (trace_pass_fl(&trace_perf_key))			    \
+			trace_performance_fl(TRACE_CONTEXT, __LINE__,       \
+					     getnanotime() - (start),	    \
+					     __VA_ARGS__);		    \
+	} while(0)
 
 /* backend functions, use non-*fl macros instead */
 __attribute__((format (printf, 4, 5)))
@@ -110,6 +129,9 @@ 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, ...);
+inline int trace_pass_fl(struct trace_key *key) {
+	return key->fd || !key->initialized;
+}
 
 #endif /* HAVE_VARIADIC_MACROS */
 
-- 
2.14.1