Merge branch 'gk/tracing-optimization'

The tracing infrastructure has been optimized for cases where no
tracing is requested.

* gk/tracing-optimization:
  trace: improve performance while category is disabled
  trace: remove trace key normalization

2 files changed, 48 insertions, 40 deletions

diff --git a/trace.c b/trace.c
index cb1293ed33..b7530b51a9 100644
--- a/trace.c
+++ b/trace.c
@@ -24,26 +24,14 @@
 #include "cache.h"
 #include "quote.h"
 
-/*
- * "Normalize" a key argument by converting NULL to our trace_default,
- * and otherwise passing through the value. All caller-facing functions
- * should normalize their inputs in this way, though most get it
- * for free by calling get_trace_fd() (directly or indirectly).
- */
-static void normalize_trace_key(struct trace_key **key)
-{
-	static struct trace_key trace_default = { "GIT_TRACE" };
-	if (!*key)
-		*key = &trace_default;
-}
+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)
 {
 	const char *trace;
 
-	normalize_trace_key(&key);
-
 	/* don't open twice */
 	if (key->initialized)
 		return key->fd;
@@ -81,8 +69,6 @@ static int get_trace_fd(struct trace_key *key)
 
 void trace_disable(struct trace_key *key)
 {
-	normalize_trace_key(&key);
-
 	if (key->need_close)
 		close(key->fd);
 	key->fd = 0;
@@ -128,7 +114,6 @@ static int prepare_trace_line(const char *file, int line,
 static void trace_write(struct trace_key *key, const void *buf, unsigned len)
 {
 	if (write_in_full(get_trace_fd(key), buf, len) < 0) {
-		normalize_trace_key(&key);
 		warning("unable to write trace for %s: %s",
 			key->key, strerror(errno));
 		trace_disable(key);
@@ -167,13 +152,13 @@ static void trace_argv_vprintf_fl(const char *file, int line,
 {
 	struct strbuf buf = STRBUF_INIT;
 
-	if (!prepare_trace_line(file, line, NULL, &buf))
+	if (!prepare_trace_line(file, line, &trace_default_key, &buf))
 		return;
 
 	strbuf_vaddf(&buf, format, ap);
 
 	sq_quote_argv(&buf, argv, 0);
-	print_trace_line(NULL, &buf);
+	print_trace_line(&trace_default_key, &buf);
 }
 
 void trace_strbuf_fl(const char *file, int line, struct trace_key *key,
@@ -188,8 +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)
@@ -215,7 +198,7 @@ void trace_printf(const char *format, ...)
 {
 	va_list ap;
 	va_start(ap, format);
-	trace_vprintf_fl(NULL, 0, NULL, format, ap);
+	trace_vprintf_fl(NULL, 0, &trace_default_key, format, ap);
 	va_end(ap);
 }
 
diff --git a/trace.h b/trace.h
index 179b249c59..88055abef7 100644
--- a/trace.h
+++ b/trace.h
@@ -11,7 +11,10 @@ struct trace_key {
 	unsigned int  need_close : 1;
 };
 
+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);
@@ -77,24 +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__, NULL, __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(&trace_perf_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)))
@@ -108,6 +129,10 @@ 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, ...);
+static inline int trace_pass_fl(struct trace_key *key)
+{
+	return key->fd || !key->initialized;
+}
 
 #endif /* HAVE_VARIADIC_MACROS */