[PATCH v5 00/11] add performance tracing facility

[PATCH v5 00/11] add performance tracing facility

[Karsten Blees]

Here's v5 of the performance tracing patch series, now including a bunch of cleanups and adding timestamp, file and line to all trace output.

I'm particularly interested in feedback for the output format. As file names have different lengths, printing file:line as prefix results in unaligned output:

 > GIT_TRACE=1 git stash list
 00:12:10.544266 git.c:512 trace: exec: 'git-stash' 'list'
 00:12:10.544266 run-command.c:337 trace: run_command: 'git-stash' 'list'
 00:12:10.649779 git.c:312 trace: built-in: git 'rev-parse' '--git-dir'

We could add separators to make it easier to parse, e.g.:

 > GIT_TRACE=1 git stash list
 [00:12:10.544266 git.c:512] trace: exec: 'git-stash' 'list'
 [00:12:10.544266 run-command.c:337] trace: run_command: 'git-stash' 'list'
 [00:12:10.649779 git.c:312] trace: built-in: git 'rev-parse' '--git-dir'

Or print file:line at the end (but what about multi-line messages, such as packet-trace?):

 > GIT_TRACE=1 git stash list
 00:12:10.544266 trace: exec: 'git-stash' 'list' (git.c:512)
 00:12:10.544266 trace: run_command: 'git-stash' 'list' (run-command.c:337)
 00:12:10.649779 trace: built-in: git 'rev-parse' '--git-dir' (git.c:312)


Karsten Blees (11):
  trace: move trace declarations from cache.h to new trace.h
  trace: consistently name the format parameter
  trace: remove redundant printf format attribute
  trace: factor out printing to the trace file
  trace: add infrastructure to augment trace output with additional info
  trace: add current timestamp to all trace output
  trace: move code around, in preparation to file:line output
  trace: add 'file:line' to all trace output
  trace: add high resolution timer function to debug performance issues
  trace: add trace_performance facility to debug performance issues
  git: add performance tracing for git's main() function to debug
    scripts

 Makefile          |   7 ++
 cache.h           |  13 +--
 config.mak.uname  |   1 +
 git-compat-util.h |   4 +
 git.c             |   2 +
 trace.c           | 304 +++++++++++++++++++++++++++++++++++++++++++++++-------
 trace.h           |  96 +++++++++++++++++
 7 files changed, 379 insertions(+), 48 deletions(-)
 create mode 100644 trace.h

-- 
1.9.2.msysgit.0.501.gaeecf09

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[PATCH v5 01/11] trace: move trace declarations from cache.h to new trace.h

[Karsten Blees]

Also include direct dependencies (strbuf.h and git-compat-util.h for
__attribute__) so that trace.h can be used independently of cache.h, e.g.
in test programs.

Signed-off-by: Karsten Blees <blees@dcon.de>
---
 cache.h | 13 ++-----------
 trace.h | 17 +++++++++++++++++
 2 files changed, 19 insertions(+), 11 deletions(-)
 create mode 100644 trace.h

diff --git a/cache.h b/cache.h
index 1e4b4f0..79ac940 100644
--- a/cache.h
+++ b/cache.h
@@ -7,6 +7,7 @@
 #include "advice.h"
 #include "gettext.h"
 #include "convert.h"
+#include "trace.h"
 
 #include SHA1_HEADER
 #ifndef git_SHA_CTX
@@ -1378,17 +1379,7 @@ extern void *alloc_tag_node(void);
 extern void *alloc_object_node(void);
 extern void alloc_report(void);
 
-/* trace.c */
-__attribute__((format (printf, 1, 2)))
-extern void trace_printf(const char *format, ...);
-__attribute__((format (printf, 2, 3)))
-extern void trace_argv_printf(const char **argv, const char *format, ...);
-extern void trace_repo_setup(const char *prefix);
-extern int trace_want(const char *key);
-__attribute__((format (printf, 2, 3)))
-extern void trace_printf_key(const char *key, const char *fmt, ...);
-extern void trace_strbuf(const char *key, const struct strbuf *buf);
-
+/* pkt-line.c */
 void packet_trace_identity(const char *prog);
 
 /* add */
diff --git a/trace.h b/trace.h
new file mode 100644
index 0000000..6cc4541
--- /dev/null
+++ b/trace.h
@@ -0,0 +1,17 @@
+#ifndef TRACE_H
+#define TRACE_H
+
+#include "git-compat-util.h"
+#include "strbuf.h"
+
+__attribute__((format (printf, 1, 2)))
+extern void trace_printf(const char *format, ...);
+__attribute__((format (printf, 2, 3)))
+extern void trace_argv_printf(const char **argv, const char *format, ...);
+extern void trace_repo_setup(const char *prefix);
+extern int trace_want(const char *key);
+__attribute__((format (printf, 2, 3)))
+extern void trace_printf_key(const char *key, const char *fmt, ...);
+extern void trace_strbuf(const char *key, const struct strbuf *buf);
+
+#endif /* TRACE_H */
-- 
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[PATCH v5 02/11] trace: consistently name the format parameter

[Karsten Blees]

The format parameter to trace_printf functions is sometimes abbreviated
'fmt'. Rename to 'format' everywhere (consistent with POSIX' printf
specification).

Signed-off-by: Karsten Blees <blees@dcon.de>
---
 trace.c | 22 +++++++++++-----------
 trace.h |  2 +-
 2 files changed, 12 insertions(+), 12 deletions(-)

diff --git a/trace.c b/trace.c
index 08180a9..37a7fa9 100644
--- a/trace.c
+++ b/trace.c
@@ -62,7 +62,7 @@ static int get_trace_fd(const char *key, int *need_close)
 static const char err_msg[] = "Could not trace into fd given by "
 	"GIT_TRACE environment variable";
 
-static void trace_vprintf(const char *key, const char *fmt, va_list ap)
+static void trace_vprintf(const char *key, const char *format, va_list ap)
 {
 	struct strbuf buf = STRBUF_INIT;
 
@@ -70,25 +70,25 @@ static void trace_vprintf(const char *key, const char *fmt, va_list ap)
 		return;
 
 	set_try_to_free_routine(NULL);	/* is never reset */
-	strbuf_vaddf(&buf, fmt, ap);
+	strbuf_vaddf(&buf, format, ap);
 	trace_strbuf(key, &buf);
 	strbuf_release(&buf);
 }
 
 __attribute__((format (printf, 2, 3)))
-void trace_printf_key(const char *key, const char *fmt, ...)
+void trace_printf_key(const char *key, const char *format, ...)
 {
 	va_list ap;
-	va_start(ap, fmt);
-	trace_vprintf(key, fmt, ap);
+	va_start(ap, format);
+	trace_vprintf(key, format, ap);
 	va_end(ap);
 }
 
-void trace_printf(const char *fmt, ...)
+void trace_printf(const char *format, ...)
 {
 	va_list ap;
-	va_start(ap, fmt);
-	trace_vprintf("GIT_TRACE", fmt, ap);
+	va_start(ap, format);
+	trace_vprintf("GIT_TRACE", format, ap);
 	va_end(ap);
 }
 
@@ -106,7 +106,7 @@ void trace_strbuf(const char *key, const struct strbuf *buf)
 		close(fd);
 }
 
-void trace_argv_printf(const char **argv, const char *fmt, ...)
+void trace_argv_printf(const char **argv, const char *format, ...)
 {
 	struct strbuf buf = STRBUF_INIT;
 	va_list ap;
@@ -117,8 +117,8 @@ void trace_argv_printf(const char **argv, const char *fmt, ...)
 		return;
 
 	set_try_to_free_routine(NULL);	/* is never reset */
-	va_start(ap, fmt);
-	strbuf_vaddf(&buf, fmt, ap);
+	va_start(ap, format);
+	strbuf_vaddf(&buf, format, ap);
 	va_end(ap);
 
 	sq_quote_argv(&buf, argv, 0);
diff --git a/trace.h b/trace.h
index 6cc4541..8fea50b 100644
--- a/trace.h
+++ b/trace.h
@@ -11,7 +11,7 @@ extern void trace_argv_printf(const char **argv, const char *format, ...);
 extern void trace_repo_setup(const char *prefix);
 extern int trace_want(const char *key);
 __attribute__((format (printf, 2, 3)))
-extern void trace_printf_key(const char *key, const char *fmt, ...);
+extern void trace_printf_key(const char *key, const char *format, ...);
 extern void trace_strbuf(const char *key, const struct strbuf *buf);
 
 #endif /* TRACE_H */
-- 
1.9.2.msysgit.0.501.gaeecf09

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[PATCH v5 03/11] trace: remove redundant printf format attribute

[Karsten Blees]

trace_printf_key() is the only non-static function that duplicates the
printf format attribute in the .c file, remove it for consistency.

Signed-off-by: Karsten Blees <blees@dcon.de>
---
 trace.c | 1 -
 1 file changed, 1 deletion(-)

diff --git a/trace.c b/trace.c
index 37a7fa9..3e31558 100644
--- a/trace.c
+++ b/trace.c
@@ -75,7 +75,6 @@ static void trace_vprintf(const char *key, const char *format, va_list ap)
 	strbuf_release(&buf);
 }
 
-__attribute__((format (printf, 2, 3)))
 void trace_printf_key(const char *key, const char *format, ...)
 {
 	va_list ap;
-- 
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[PATCH v5 04/11] trace: factor out printing to the trace file

[Karsten Blees]

Opening and writing to the trace file is currently duplicated in
trace_strbuf() and trace_argv_printf(). Factor out this logic to prepare
for adding timestamp and file:line to trace output.

In case of trace_argv_printf(), this adds an additional trace_want() check
to prevent unnecessary string formatting.

Signed-off-by: Karsten Blees <blees@dcon.de>
---
 trace.c | 37 +++++++++++++++++++------------------
 1 file changed, 19 insertions(+), 18 deletions(-)

diff --git a/trace.c b/trace.c
index 3e31558..b7ca51b 100644
--- a/trace.c
+++ b/trace.c
@@ -62,6 +62,21 @@ static int get_trace_fd(const char *key, int *need_close)
 static const char err_msg[] = "Could not trace into fd given by "
 	"GIT_TRACE environment variable";
 
+/* Print 'buf' verbatim to trace file designated by env var 'key' */
+static void do_trace_print(const char *key, const struct strbuf *buf)
+{
+	int fd, need_close = 0;
+
+	fd = get_trace_fd(key, &need_close);
+	if (!fd)
+		return;
+
+	write_or_whine_pipe(fd, buf->buf, buf->len, err_msg);
+
+	if (need_close)
+		close(fd);
+}
+
 static void trace_vprintf(const char *key, const char *format, va_list ap)
 {
 	struct strbuf buf = STRBUF_INIT;
@@ -71,7 +86,7 @@ static void trace_vprintf(const char *key, const char *format, va_list ap)
 
 	set_try_to_free_routine(NULL);	/* is never reset */
 	strbuf_vaddf(&buf, format, ap);
-	trace_strbuf(key, &buf);
+	do_trace_print(key, &buf);
 	strbuf_release(&buf);
 }
 
@@ -93,26 +108,15 @@ void trace_printf(const char *format, ...)
 
 void trace_strbuf(const char *key, const struct strbuf *buf)
 {
-	int fd, need_close = 0;
-
-	fd = get_trace_fd(key, &need_close);
-	if (!fd)
-		return;
-
-	write_or_whine_pipe(fd, buf->buf, buf->len, err_msg);
-
-	if (need_close)
-		close(fd);
+	do_trace_print(key, buf);
 }
 
 void trace_argv_printf(const char **argv, const char *format, ...)
 {
 	struct strbuf buf = STRBUF_INIT;
 	va_list ap;
-	int fd, need_close = 0;
 
-	fd = get_trace_fd("GIT_TRACE", &need_close);
-	if (!fd)
+	if (!trace_want("GIT_TRACE"))
 		return;
 
 	set_try_to_free_routine(NULL);	/* is never reset */
@@ -122,11 +126,8 @@ void trace_argv_printf(const char **argv, const char *format, ...)
 
 	sq_quote_argv(&buf, argv, 0);
 	strbuf_addch(&buf, '\n');
-	write_or_whine_pipe(fd, buf.buf, buf.len, err_msg);
+	do_trace_print("GIT_TRACE", &buf);
 	strbuf_release(&buf);
-
-	if (need_close)
-		close(fd);
 }
 
 static const char *quote_crnl(const char *path)
-- 
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[PATCH v5 05/11] trace: add infrastructure to augment trace output with additional info

[Karsten Blees]

To be able to add a common prefix or suffix to all trace output (e.g.
a timestamp or file:line of the caller), factor out common setup and
cleanup tasks of the trace* functions.

When adding a common prefix, it makes sense that the output of each trace
call starts on a new line. Add '\n' in case the caller forgot.

Note that this explicitly limits trace output to line-by-line, it is no
longer possible to trace-print just part of a line. Until now, this was
just an implicit assumption (trace-printing part of a line worked, but
messed up the trace file if multiple threads or processes were involved).

Thread-safety / inter-process-safety is also the reason why we need to do
the prefixing and suffixing in memory rather than issuing multiple write()
calls. Write_or_whine_pipe() / xwrite() is atomic unless the size exceeds
MAX_IO_SIZE (8MB, see wrapper.c). In case of trace_strbuf, this costs an
additional string copy (which should be irrelevant for performance in light
of actual file IO).

While we're at it, rename trace_strbuf's 'buf' argument, which suggests
that the function is modifying the buffer. Trace_strbuf() currently is the
only trace API that can print arbitrary binary data (without barfing on
'%' or stopping at '\0'), so 'data' seems more appropriate.

Signed-off-by: Karsten Blees <blees@dcon.de>
---
 trace.c | 45 ++++++++++++++++++++++++++++++++++-----------
 trace.h |  2 +-
 2 files changed, 35 insertions(+), 12 deletions(-)

diff --git a/trace.c b/trace.c
index b7ca51b..c920429 100644
--- a/trace.c
+++ b/trace.c
@@ -77,17 +77,37 @@ static void do_trace_print(const char *key, const struct strbuf *buf)
 		close(fd);
 }
 
+static int prepare_trace_line(const char *key, struct strbuf *buf)
+{
+	if (!trace_want(key))
+		return 0;
+
+	set_try_to_free_routine(NULL);	/* is never reset */
+
+	/* add line prefix here */
+
+	return 1;
+}
+
+static void print_trace_line(const char *key, struct strbuf *buf)
+{
+	/* append newline if missing */
+	if (buf->len && buf->buf[buf->len - 1] != '\n')
+		strbuf_addch(buf, '\n');
+
+	do_trace_print(key, buf);
+	strbuf_release(buf);
+}
+
 static void trace_vprintf(const char *key, const char *format, va_list ap)
 {
 	struct strbuf buf = STRBUF_INIT;
 
-	if (!trace_want(key))
+	if (!prepare_trace_line(key, &buf))
 		return;
 
-	set_try_to_free_routine(NULL);	/* is never reset */
 	strbuf_vaddf(&buf, format, ap);
-	do_trace_print(key, &buf);
-	strbuf_release(&buf);
+	print_trace_line(key, &buf);
 }
 
 void trace_printf_key(const char *key, const char *format, ...)
@@ -106,9 +126,15 @@ void trace_printf(const char *format, ...)
 	va_end(ap);
 }
 
-void trace_strbuf(const char *key, const struct strbuf *buf)
+void trace_strbuf(const char *key, const struct strbuf *data)
 {
-	do_trace_print(key, buf);
+	struct strbuf buf = STRBUF_INIT;
+
+	if (!prepare_trace_line(key, &buf))
+		return;
+
+	strbuf_addbuf(&buf, data);
+	print_trace_line(key, &buf);
 }
 
 void trace_argv_printf(const char **argv, const char *format, ...)
@@ -116,18 +142,15 @@ void trace_argv_printf(const char **argv, const char *format, ...)
 	struct strbuf buf = STRBUF_INIT;
 	va_list ap;
 
-	if (!trace_want("GIT_TRACE"))
+	if (!prepare_trace_line("GIT_TRACE", &buf))
 		return;
 
-	set_try_to_free_routine(NULL);	/* is never reset */
 	va_start(ap, format);
 	strbuf_vaddf(&buf, format, ap);
 	va_end(ap);
 
 	sq_quote_argv(&buf, argv, 0);
-	strbuf_addch(&buf, '\n');
-	do_trace_print("GIT_TRACE", &buf);
-	strbuf_release(&buf);
+	print_trace_line("GIT_TRACE", &buf);
 }
 
 static const char *quote_crnl(const char *path)
diff --git a/trace.h b/trace.h
index 8fea50b..e03db2f 100644
--- a/trace.h
+++ b/trace.h
@@ -12,6 +12,6 @@ extern void trace_repo_setup(const char *prefix);
 extern int trace_want(const char *key);
 __attribute__((format (printf, 2, 3)))
 extern void trace_printf_key(const char *key, const char *format, ...);
-extern void trace_strbuf(const char *key, const struct strbuf *buf);
+extern void trace_strbuf(const char *key, const struct strbuf *data);
 
 #endif /* TRACE_H */
-- 
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[PATCH v5 06/11] trace: add current timestamp to all trace output

[Karsten Blees]

This is useful to tell apart trace output of separate test runs.

It can also be used for basic, coarse-grained performance analysis. Note
that the accuracy is tainted by writing to the trace file, and you have to
calculate the deltas yourself (which is next to impossible if multiple
threads or processes are involved).

Signed-off-by: Karsten Blees <blees@dcon.de>
---
 trace.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/trace.c b/trace.c
index c920429..5a3393a 100644
--- a/trace.c
+++ b/trace.c
@@ -79,12 +79,21 @@ static void do_trace_print(const char *key, const struct strbuf *buf)
 
 static int prepare_trace_line(const char *key, struct strbuf *buf)
 {
+	struct timeval tv;
+	struct tm tm;
+	time_t secs;
+
 	if (!trace_want(key))
 		return 0;
 
 	set_try_to_free_routine(NULL);	/* is never reset */
 
-	/* add line prefix here */
+	/* print current timestamp */
+	gettimeofday(&tv, NULL);
+	secs = tv.tv_sec;
+	localtime_r(&secs, &tm);
+	strbuf_addf(buf, "%02d:%02d:%02d.%06ld ", tm.tm_hour, tm.tm_min,
+		    tm.tm_sec, tv.tv_usec);
 
 	return 1;
 }
-- 
1.9.2.msysgit.0.501.gaeecf09

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[PATCH v5 07/11] trace: move code around, in preparation to file:line output

[Karsten Blees]

No functional changes, just move stuff around so that the next patch isn't
that ugly...

Signed-off-by: Karsten Blees <blees@dcon.de>
---
 trace.c | 36 ++++++++++++++++++------------------
 trace.h | 12 ++++++++----
 2 files changed, 26 insertions(+), 22 deletions(-)

diff --git a/trace.c b/trace.c
index 5a3393a..c86d33c 100644
--- a/trace.c
+++ b/trace.c
@@ -119,20 +119,20 @@ static void trace_vprintf(const char *key, const char *format, va_list ap)
 	print_trace_line(key, &buf);
 }
 
-void trace_printf_key(const char *key, const char *format, ...)
+void trace_argv_printf(const char **argv, const char *format, ...)
 {
+	struct strbuf buf = STRBUF_INIT;
 	va_list ap;
-	va_start(ap, format);
-	trace_vprintf(key, format, ap);
-	va_end(ap);
-}
 
-void trace_printf(const char *format, ...)
-{
-	va_list ap;
+	if (!prepare_trace_line("GIT_TRACE", &buf))
+		return;
+
 	va_start(ap, format);
-	trace_vprintf("GIT_TRACE", format, ap);
+	strbuf_vaddf(&buf, format, ap);
 	va_end(ap);
+
+	sq_quote_argv(&buf, argv, 0);
+	print_trace_line("GIT_TRACE", &buf);
 }
 
 void trace_strbuf(const char *key, const struct strbuf *data)
@@ -146,20 +146,20 @@ void trace_strbuf(const char *key, const struct strbuf *data)
 	print_trace_line(key, &buf);
 }
 
-void trace_argv_printf(const char **argv, const char *format, ...)
+void trace_printf(const char *format, ...)
 {
-	struct strbuf buf = STRBUF_INIT;
 	va_list ap;
-
-	if (!prepare_trace_line("GIT_TRACE", &buf))
-		return;
-
 	va_start(ap, format);
-	strbuf_vaddf(&buf, format, ap);
+	trace_vprintf("GIT_TRACE", format, ap);
 	va_end(ap);
+}
 
-	sq_quote_argv(&buf, argv, 0);
-	print_trace_line("GIT_TRACE", &buf);
+void trace_printf_key(const char *key, const char *format, ...)
+{
+	va_list ap;
+	va_start(ap, format);
+	trace_vprintf(key, format, ap);
+	va_end(ap);
 }
 
 static const char *quote_crnl(const char *path)
diff --git a/trace.h b/trace.h
index e03db2f..5c7f2dc 100644
--- a/trace.h
+++ b/trace.h
@@ -4,14 +4,18 @@
 #include "git-compat-util.h"
 #include "strbuf.h"
 
-__attribute__((format (printf, 1, 2)))
-extern void trace_printf(const char *format, ...);
-__attribute__((format (printf, 2, 3)))
-extern void trace_argv_printf(const char **argv, const char *format, ...);
 extern void trace_repo_setup(const char *prefix);
 extern int trace_want(const char *key);
+
+__attribute__((format (printf, 1, 2)))
+extern void trace_printf(const char *format, ...);
+
 __attribute__((format (printf, 2, 3)))
 extern void trace_printf_key(const char *key, const char *format, ...);
+
+__attribute__((format (printf, 2, 3)))
+extern void trace_argv_printf(const char **argv, const char *format, ...);
+
 extern void trace_strbuf(const char *key, const struct strbuf *data);
 
 #endif /* TRACE_H */
-- 
1.9.2.msysgit.0.501.gaeecf09

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[PATCH v5 08/11] trace: add 'file:line' to all trace output

[Karsten Blees]

This is useful to see where trace output came from.

Add 'const char *file, int line' parameters to the printing functions and
rename them to *_fl.

Add trace_printf* and trace_strbuf macros resolving to the *_fl functions
and let the preprocessor fill in __FILE__ and __LINE__.

As the trace_printf* functions take a variable number of arguments, this
requires variadic macros (i.e. '#define foo(...) foo_impl(__VA_ARGS__)'.
Though part of C99, it is unclear whether older compilers support this.
Thus keep the old functions and only enable variadic macros for GNUC and
MSVC 2005+ (_MSC_VER 1400). This has the nice side effect that the old
C-style declarations serve as documentation how the macros are to be used.

Signed-off-by: Karsten Blees <blees@dcon.de>
---
 git-compat-util.h |  4 ++++
 trace.c           | 69 +++++++++++++++++++++++++++++++++++++++++++++----------
 trace.h           | 49 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 110 insertions(+), 12 deletions(-)

diff --git a/git-compat-util.h b/git-compat-util.h
index 7849d31..e5a773b 100644
--- a/git-compat-util.h
+++ b/git-compat-util.h
@@ -700,6 +700,10 @@ void git_qsort(void *base, size_t nmemb, size_t size,
 #endif
 #endif
 
+#if defined(__GNUC__) || (_MSC_VER >= 1400)
+#define HAVE_VARIADIC_MACROS 1
+#endif
+
 /*
  * Preserves errno, prints a message, but gives no warning for ENOENT.
  * Always returns the return value of unlink(2).
diff --git a/trace.c b/trace.c
index c86d33c..231e24a 100644
--- a/trace.c
+++ b/trace.c
@@ -77,7 +77,8 @@ static void do_trace_print(const char *key, const struct strbuf *buf)
 		close(fd);
 }
 
-static int prepare_trace_line(const char *key, struct strbuf *buf)
+static int prepare_trace_line(const char *file, int line, const char *key,
+			      struct strbuf *buf)
 {
 	struct timeval tv;
 	struct tm tm;
@@ -95,6 +96,11 @@ static int prepare_trace_line(const char *key, struct strbuf *buf)
 	strbuf_addf(buf, "%02d:%02d:%02d.%06ld ", tm.tm_hour, tm.tm_min,
 		    tm.tm_sec, tv.tv_usec);
 
+#ifdef HAVE_VARIADIC_MACROS
+	/* print file:line */
+	strbuf_addf(buf, "%s:%d ", file, line);
+#endif
+
 	return 1;
 }
 
@@ -108,49 +114,52 @@ static void print_trace_line(const char *key, struct strbuf *buf)
 	strbuf_release(buf);
 }
 
-static void trace_vprintf(const char *key, const char *format, va_list ap)
+static void trace_vprintf_fl(const char *file, int line, const char *key,
+			     const char *format, va_list ap)
 {
 	struct strbuf buf = STRBUF_INIT;
 
-	if (!prepare_trace_line(key, &buf))
+	if (!prepare_trace_line(file, line, key, &buf))
 		return;
 
 	strbuf_vaddf(&buf, format, ap);
 	print_trace_line(key, &buf);
 }
 
-void trace_argv_printf(const char **argv, const char *format, ...)
+static void trace_argv_vprintf_fl(const char *file, int line,
+				  const char **argv, const char *format,
+				  va_list ap)
 {
 	struct strbuf buf = STRBUF_INIT;
-	va_list ap;
 
-	if (!prepare_trace_line("GIT_TRACE", &buf))
+	if (!prepare_trace_line(file, line, "GIT_TRACE", &buf))
 		return;
 
-	va_start(ap, format);
 	strbuf_vaddf(&buf, format, ap);
-	va_end(ap);
 
 	sq_quote_argv(&buf, argv, 0);
 	print_trace_line("GIT_TRACE", &buf);
 }
 
-void trace_strbuf(const char *key, const struct strbuf *data)
+void trace_strbuf_fl(const char *file, int line, const char *key,
+		     const struct strbuf *data)
 {
 	struct strbuf buf = STRBUF_INIT;
 
-	if (!prepare_trace_line(key, &buf))
+	if (!prepare_trace_line(file, line, key, &buf))
 		return;
 
 	strbuf_addbuf(&buf, data);
 	print_trace_line(key, &buf);
 }
 
+#ifndef HAVE_VARIADIC_MACROS
+
 void trace_printf(const char *format, ...)
 {
 	va_list ap;
 	va_start(ap, format);
-	trace_vprintf("GIT_TRACE", format, ap);
+	trace_vprintf_fl(NULL, 0, "GIT_TRACE", format, ap);
 	va_end(ap);
 }
 
@@ -158,10 +167,46 @@ void trace_printf_key(const char *key, const char *format, ...)
 {
 	va_list ap;
 	va_start(ap, format);
-	trace_vprintf(key, format, ap);
+	trace_vprintf_fl(NULL, 0, key, format, ap);
 	va_end(ap);
 }
 
+void trace_argv_printf(const char **argv, const char *format, ...)
+{
+	va_list ap;
+	va_start(ap, format);
+	trace_argv_vprintf_fl(NULL, 0, argv, format, ap);
+	va_end(ap);
+}
+
+void trace_strbuf(const char *key, const struct strbuf *data)
+{
+	trace_strbuf_fl(NULL, 0, key, data);
+}
+
+#else
+
+void trace_printf_key_fl(const char *file, int line, const char *key,
+			 const char *format, ...)
+{
+	va_list ap;
+	va_start(ap, format);
+	trace_vprintf_fl(file, line, key, format, ap);
+	va_end(ap);
+}
+
+void trace_argv_printf_fl(const char *file, int line, const char **argv,
+			  const char *format, ...)
+{
+	va_list ap;
+	va_start(ap, format);
+	trace_argv_vprintf_fl(file, line, argv, format, ap);
+	va_end(ap);
+}
+
+#endif /* HAVE_VARIADIC_MACROS */
+
+
 static const char *quote_crnl(const char *path)
 {
 	static char new_path[PATH_MAX];
diff --git a/trace.h b/trace.h
index 5c7f2dc..916dc2b 100644
--- a/trace.h
+++ b/trace.h
@@ -7,6 +7,8 @@
 extern void trace_repo_setup(const char *prefix);
 extern int trace_want(const char *key);
 
+#ifndef HAVE_VARIADIC_MACROS
+
 __attribute__((format (printf, 1, 2)))
 extern void trace_printf(const char *format, ...);
 
@@ -18,4 +20,51 @@ extern void trace_argv_printf(const char **argv, const char *format, ...);
 
 extern void trace_strbuf(const char *key, const struct strbuf *data);
 
+#else
+
+/*
+ * Macros to add file:line - see above for C-style declarations of how these
+ * should be used.
+ */
+
+/*
+ * Note: with C99 variadic macros, __VA_ARGS__ must include the last fixed
+ * parameter ('format' in this case). Otherwise, a call without variable
+ * arguments will have a surplus ','. E.g.:
+ *
+ *  #define foo(format, ...) bar(format, __VA_ARGS__)
+ *  foo("test");
+ *
+ * will expand to
+ *
+ *  bar("test",);
+ *
+ * which is invalid (note the ',)'). With GNUC, '##__VA_ARGS__' drops the
+ * comma, but this is non-standard.
+ */
+
+#define trace_printf(...) \
+	trace_printf_key_fl(__FILE__, __LINE__, "GIT_TRACE", __VA_ARGS__)
+
+#define trace_printf_key(key, ...) \
+	trace_printf_key_fl(__FILE__, __LINE__, key, __VA_ARGS__)
+
+#define trace_argv_printf(argv, ...) \
+	trace_argv_printf_fl(__FILE__, __LINE__, argv, __VA_ARGS__)
+
+#define trace_strbuf(key, data) \
+	trace_strbuf_fl(__FILE__, __LINE__, key, data)
+
+/* backend functions, use non-*fl macros instead */
+__attribute__((format (printf, 4, 5)))
+extern void trace_printf_key_fl(const char *file, int line, const char *key,
+				const char *format, ...);
+__attribute__((format (printf, 4, 5)))
+extern void trace_argv_printf_fl(const char *file, int line, const char **argv,
+				 const char *format, ...);
+extern void trace_strbuf_fl(const char *file, int line, const char *key,
+			    const struct strbuf *data);
+
+#endif /* HAVE_VARIADIC_MACROS */
+
 #endif /* TRACE_H */
-- 
1.9.2.msysgit.0.501.gaeecf09

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[PATCH v5 09/11] trace: add high resolution timer function to debug performance issues

[Karsten Blees]

Add a getnanotime() function that returns nanoseconds since 01/01/1970 as
unsigned 64-bit integer (i.e. overflows in july 2554). This is easier to
work with than e.g. struct timeval or struct timespec. Basing the timer on
the epoch allows using the results (div 10e9) with other time-related APIs.

To simplify adaption to different platforms, split the implementation into
a common getnanotime() and a platform-specific highres_nanos() function.

The common getnanotime() function handles errors, falling back to
gettimeofday() if highres_nanos() isn't implemented or doesn't work.

getnanotime() is also responsible for normalizing to the epoch. The offset
to the system clock is calculated only once on initialization, i.e.
manually setting the system clock has no impact on the timer (except if
the fallback gettimeofday() is in use). Git processes are typically short
lived, so we don't need to handle clock drift.

The highres_nanos() function returns monotonically increasing nanoseconds
relative to some arbitrary point in time (e.g. system boot), or 0 on
failure. Providing platform-specific implementations should be relatively
easy, e.g. adapting to clock_gettime() as defined by the POSIX realtime
extensions is seven lines of code.

This version includes highres_nanos() implementations for:
 * Linux: using clock_gettime(CLOCK_MONOTONIC)
 * Windows: using QueryPerformanceCounter()

Todo:
 * enable clock_gettime() on more platforms
 * add Mac OSX version, e.g. using mach_absolute_time + mach_timebase_info

Signed-off-by: Karsten Blees <blees@dcon.de>
---
 Makefile         |  7 +++++
 config.mak.uname |  1 +
 trace.c          | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 trace.h          |  1 +
 4 files changed, 91 insertions(+)

diff --git a/Makefile b/Makefile
index 07ea105..80f4390 100644
--- a/Makefile
+++ b/Makefile
@@ -340,6 +340,8 @@ all::
 #
 # Define GMTIME_UNRELIABLE_ERRORS if your gmtime() function does not
 # return NULL when it receives a bogus time_t.
+#
+# Define HAVE_CLOCK_GETTIME if your platform has clock_gettime in librt.
 
 GIT-VERSION-FILE: FORCE
 	@$(SHELL_PATH) ./GIT-VERSION-GEN
@@ -1497,6 +1499,11 @@ ifdef GMTIME_UNRELIABLE_ERRORS
 	BASIC_CFLAGS += -DGMTIME_UNRELIABLE_ERRORS
 endif
 
+ifdef HAVE_CLOCK_GETTIME
+	BASIC_CFLAGS += -DHAVE_CLOCK_GETTIME
+	EXTLIBS += -lrt
+endif
+
 ifeq ($(TCLTK_PATH),)
 NO_TCLTK = NoThanks
 endif
diff --git a/config.mak.uname b/config.mak.uname
index 1ae675b..dad2618 100644
--- a/config.mak.uname
+++ b/config.mak.uname
@@ -34,6 +34,7 @@ ifeq ($(uname_S),Linux)
 	HAVE_PATHS_H = YesPlease
 	LIBC_CONTAINS_LIBINTL = YesPlease
 	HAVE_DEV_TTY = YesPlease
+	HAVE_CLOCK_GETTIME = YesPlease
 endif
 ifeq ($(uname_S),GNU/kFreeBSD)
 	HAVE_ALLOCA_H = YesPlease
diff --git a/trace.c b/trace.c
index 231e24a..4bd52f2 100644
--- a/trace.c
+++ b/trace.c
@@ -264,3 +264,85 @@ int trace_want(const char *key)
 		return 0;
 	return 1;
 }
+
+#ifdef HAVE_CLOCK_GETTIME
+
+static inline uint64_t highres_nanos(void)
+{
+	struct timespec ts;
+	if (clock_gettime(CLOCK_MONOTONIC, &ts))
+		return 0;
+	return (uint64_t) ts.tv_sec * 1000000000 + ts.tv_nsec;
+}
+
+#elif defined (GIT_WINDOWS_NATIVE)
+
+static inline uint64_t highres_nanos(void)
+{
+	static uint64_t high_ns, scaled_low_ns;
+	static int scale;
+	LARGE_INTEGER cnt;
+
+	if (!scale) {
+		if (!QueryPerformanceFrequency(&cnt))
+			return 0;
+
+		/* high_ns = number of ns per cnt.HighPart */
+		high_ns = (1000000000LL << 32) / (uint64_t) cnt.QuadPart;
+
+		/*
+		 * Number of ns per cnt.LowPart is 10^9 / frequency (or
+		 * high_ns >> 32). For maximum precision, we scale this factor
+		 * so that it just fits within 32 bit (i.e. won't overflow if
+		 * multiplied with cnt.LowPart).
+		 */
+		scaled_low_ns = high_ns;
+		scale = 32;
+		while (scaled_low_ns >= 0x100000000LL) {
+			scaled_low_ns >>= 1;
+			scale--;
+		}
+	}
+
+	/* if QPF worked on initialization, we expect QPC to work as well */
+	QueryPerformanceCounter(&cnt);
+
+	return (high_ns * cnt.HighPart) +
+	       ((scaled_low_ns * cnt.LowPart) >> scale);
+}
+
+#else
+# define highres_nanos() 0
+#endif
+
+static inline uint64_t gettimeofday_nanos(void)
+{
+	struct timeval tv;
+	gettimeofday(&tv, NULL);
+	return (uint64_t) tv.tv_sec * 1000000000 + tv.tv_usec * 1000;
+}
+
+/*
+ * Returns nanoseconds since the epoch (01/01/1970), for performance tracing
+ * (i.e. favoring high precision over wall clock time accuracy).
+ */
+inline uint64_t getnanotime(void)
+{
+	static uint64_t offset;
+	if (offset > 1) {
+		/* initialization succeeded, return offset + high res time */
+		return offset + highres_nanos();
+	} else if (offset == 1) {
+		/* initialization failed, fall back to gettimeofday */
+		return gettimeofday_nanos();
+	} else {
+		/* initialize offset if high resolution timer works */
+		uint64_t now = gettimeofday_nanos();
+		uint64_t highres = highres_nanos();
+		if (highres)
+			offset = now - highres;
+		else
+			offset = 1;
+		return now;
+	}
+}
diff --git a/trace.h b/trace.h
index 916dc2b..c4964aa 100644
--- a/trace.h
+++ b/trace.h
@@ -6,6 +6,7 @@
 
 extern void trace_repo_setup(const char *prefix);
 extern int trace_want(const char *key);
+extern uint64_t getnanotime(void);
 
 #ifndef HAVE_VARIADIC_MACROS
 
-- 
1.9.2.msysgit.0.501.gaeecf09

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[PATCH v5 10/11] trace: add trace_performance facility to debug performance issues

[Karsten Blees]

Add trace_performance and trace_performance_since macros that print a
duration and an optional printf-formatted text to the file specified in
environment variable GIT_TRACE_PERFORMANCE.

These macros, in conjunction with getnanotime(), are intended to simplify
performance measurements from within the application (i.e. profiling via
manual instrumentation, rather than using an external profiling tool).

Unless enabled via GIT_TRACE_PERFORMANCE, these macros have no noticeable
impact on performance, so that test code for well known time killers may
be shipped in release builds. Alternatively, a developer could provide an
additional performance patch (not meant for master) that allows reviewers
to reproduce performance tests more easily, e.g. on other platforms or
using their own repositories.

Usage examples:

Simple use case (measure one code section):

  uint64_t start = getnanotime();
  /* code section to measure */
  trace_performance_since(start, "foobar");

Medium use case (measure consecutive code sections):

  uint64_t start = getnanotime();
  /* first code section to measure */
  start = trace_performance_since(start, "first foobar");
  /* second code section to measure */
  trace_performance_since(start, "second foobar");

Complex use case (measure repetitive code sections):

  uint64_t t = 0;
  for (;;) {
    /* ignore */
    t -= getnanotime();
    /* code section to measure */
    t += getnanotime();
    /* ignore */
  }
  trace_performance(t, "frotz");

Signed-off-by: Karsten Blees <blees@dcon.de>
---
 trace.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
 trace.h | 24 ++++++++++++++++++++++++
 2 files changed, 73 insertions(+)

diff --git a/trace.c b/trace.c
index 4bd52f2..0551509 100644
--- a/trace.c
+++ b/trace.c
@@ -153,6 +153,27 @@ void trace_strbuf_fl(const char *file, int line, const char *key,
 	print_trace_line(key, &buf);
 }
 
+static const char *GIT_TRACE_PERFORMANCE = "GIT_TRACE_PERFORMANCE";
+
+static void trace_performance_vfl(const char *file, int line,
+				      uint64_t nanos, const char *format,
+				      va_list ap)
+{
+	struct strbuf buf = STRBUF_INIT;
+
+	if (!prepare_trace_line(file, line, GIT_TRACE_PERFORMANCE, &buf))
+		return;
+
+	strbuf_addf(&buf, "performance: %.9f s", (double) nanos / 1000000000);
+
+	if (format && *format) {
+		strbuf_addstr(&buf, ": ");
+		strbuf_vaddf(&buf, format, ap);
+	}
+
+	print_trace_line(GIT_TRACE_PERFORMANCE, &buf);
+}
+
 #ifndef HAVE_VARIADIC_MACROS
 
 void trace_printf(const char *format, ...)
@@ -184,6 +205,24 @@ void trace_strbuf(const char *key, const struct strbuf *data)
 	trace_strbuf_fl(NULL, 0, key, data);
 }
 
+uint64_t trace_performance(uint64_t nanos, const char *format, ...)
+{
+	va_list ap;
+	va_start(ap, format);
+	trace_performance_vfl(NULL, 0, nanos, format, ap);
+	va_end(ap);
+	return getnanotime();
+}
+
+uint64_t trace_performance_since(uint64_t start, const char *format, ...)
+{
+	va_list ap;
+	va_start(ap, format);
+	trace_performance_vfl(NULL, 0, getnanotime() - start, format, ap);
+	va_end(ap);
+	return getnanotime();
+}
+
 #else
 
 void trace_printf_key_fl(const char *file, int line, const char *key,
@@ -204,6 +243,16 @@ void trace_argv_printf_fl(const char *file, int line, const char **argv,
 	va_end(ap);
 }
 
+uint64_t trace_performance_fl(const char *file, int line, uint64_t nanos,
+			      const char *format, ...)
+{
+	va_list ap;
+	va_start(ap, format);
+	trace_performance_vfl(file, line, nanos, format, ap);
+	va_end(ap);
+	return getnanotime();
+}
+
 #endif /* HAVE_VARIADIC_MACROS */
 
 
diff --git a/trace.h b/trace.h
index c4964aa..9687563 100644
--- a/trace.h
+++ b/trace.h
@@ -21,6 +21,20 @@ extern void trace_argv_printf(const char **argv, const char *format, ...);
 
 extern void trace_strbuf(const char *key, const struct strbuf *data);
 
+/*
+ * Prints specified time (in nanoseconds) if GIT_TRACE_PERFORMANCE is enabled.
+ * Returns current time in nanoseconds.
+ */
+__attribute__((format (printf, 2, 3)))
+extern uint64_t trace_performance(uint64_t nanos, const char *format, ...);
+
+/*
+ * Prints time since 'start' if GIT_TRACE_PERFORMANCE is enabled.
+ * Returns current time in nanoseconds.
+ */
+__attribute__((format (printf, 2, 3)))
+extern uint64_t trace_performance_since(uint64_t start, const char *format, ...);
+
 #else
 
 /*
@@ -56,6 +70,13 @@ extern void trace_strbuf(const char *key, const struct strbuf *data);
 #define trace_strbuf(key, data) \
 	trace_strbuf_fl(__FILE__, __LINE__, key, data)
 
+#define trace_performance(nanos, ...) \
+	trace_performance_fl(__FILE__, __LINE__, nanos, __VA_ARGS__)
+
+#define trace_performance_since(start, ...) \
+	trace_performance_fl(__FILE__, __LINE__, getnanotime() - (start), \
+			     __VA_ARGS__)
+
 /* backend functions, use non-*fl macros instead */
 __attribute__((format (printf, 4, 5)))
 extern void trace_printf_key_fl(const char *file, int line, const char *key,
@@ -65,6 +86,9 @@ extern void trace_argv_printf_fl(const char *file, int line, const char **argv,
 				 const char *format, ...);
 extern void trace_strbuf_fl(const char *file, int line, const char *key,
 			    const struct strbuf *data);
+__attribute__((format (printf, 4, 5)))
+extern uint64_t trace_performance_fl(const char *file, int line,
+				     uint64_t nanos, const char *fmt, ...);
 
 #endif /* HAVE_VARIADIC_MACROS */
 
-- 
1.9.2.msysgit.0.501.gaeecf09

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[PATCH v5 11/11] git: add performance tracing for git's main() function to debug scripts

[Karsten Blees]

Use trace_performance to measure and print execution time and command line
arguments of the entire main() function. In constrast to the shell's 'time'
utility, which measures total time of the parent process, this logs all
involved git commands recursively. This is particularly useful to debug
performance issues of scripted commands (i.e. which git commands were
called with which parameters, and how long did they execute).

Due to git's deliberate use of exit(), the implementation uses an atexit
routine rather than just adding trace_performance_since() at the end of
main().

Usage example: > GIT_TRACE_PERFORMANCE=~/git-trace.log git stash list

Creates a log file like this:
23:57:38.638765 trace.c:405 performance: 0.000310107 s: git command: 'git' 'rev-parse' '--git-dir'
23:57:38.644387 trace.c:405 performance: 0.000261759 s: git command: 'git' 'rev-parse' '--show-toplevel'
23:57:38.646207 trace.c:405 performance: 0.000304468 s: git command: 'git' 'config' '--get-colorbool' 'color.interactive'
23:57:38.648491 trace.c:405 performance: 0.000241667 s: git command: 'git' 'config' '--get-color' 'color.interactive.help' 'red bold'
23:57:38.650465 trace.c:405 performance: 0.000243063 s: git command: 'git' 'config' '--get-color' '' 'reset'
23:57:38.654850 trace.c:405 performance: 0.025126313 s: git command: 'git' 'stash' 'list'

Signed-off-by: Karsten Blees <blees@dcon.de>
---
 git.c   |  2 ++
 trace.c | 22 ++++++++++++++++++++++
 trace.h |  1 +
 3 files changed, 25 insertions(+)

diff --git a/git.c b/git.c
index 7780572..d4daeb8 100644
--- a/git.c
+++ b/git.c
@@ -568,6 +568,8 @@ int main(int argc, char **av)
 
 	git_setup_gettext();
 
+	trace_command_performance(argv);
+
 	/*
 	 * "git-xxxx" is the same as "git xxxx", but we obviously:
 	 *
diff --git a/trace.c b/trace.c
index 0551509..9fc3921 100644
--- a/trace.c
+++ b/trace.c
@@ -395,3 +395,25 @@ inline uint64_t getnanotime(void)
 		return now;
 	}
 }
+
+static uint64_t command_start_time;
+static struct strbuf command_line = STRBUF_INIT;
+
+static void print_command_performance_atexit(void)
+{
+	trace_performance_since(command_start_time, "git command:%s",
+				command_line.buf);
+}
+
+void trace_command_performance(const char **argv)
+{
+	if (!trace_want(GIT_TRACE_PERFORMANCE))
+		return;
+
+	if (!command_start_time)
+		atexit(print_command_performance_atexit);
+
+	strbuf_reset(&command_line);
+	sq_quote_argv(&command_line, argv, 0);
+	command_start_time = getnanotime();
+}
diff --git a/trace.h b/trace.h
index 9687563..a51e731 100644
--- a/trace.h
+++ b/trace.h
@@ -7,6 +7,7 @@
 extern void trace_repo_setup(const char *prefix);
 extern int trace_want(const char *key);
 extern uint64_t getnanotime(void);
+extern void trace_command_performance(const char **argv);
 
 #ifndef HAVE_VARIADIC_MACROS
 
-- 
1.9.2.msysgit.0.501.gaeecf09

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Re: [PATCH v5 09/11] trace: add high resolution timer function to debug performance issues

[Karsten Blees]

Am 11.06.2014 10:01, schrieb Karsten Blees:
> the epoch allows using the results (div 10e9) with other time-related APIs.

s/10e9/1e9/

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Re: [PATCH v5 00/11] add performance tracing facility

[Junio C Hamano]

Karsten Blees <karsten.blees@gmail.com> writes:

> Here's v5 of the performance tracing patch series, now including a bunch of cleanups and adding timestamp, file and line to all trace output.
>
> I'm particularly interested in feedback for the output format. As file names have different lengths, printing file:line as prefix results in unaligned output:
>
>  > GIT_TRACE=1 git stash list
>  00:12:10.544266 git.c:512 trace: exec: 'git-stash' 'list'
>  00:12:10.544266 run-command.c:337 trace: run_command: 'git-stash' 'list'
>  00:12:10.649779 git.c:312 trace: built-in: git 'rev-parse' '--git-dir'
>
> We could add separators to make it easier to parse, e.g.:
>
>  > GIT_TRACE=1 git stash list
>  [00:12:10.544266 git.c:512] trace: exec: 'git-stash' 'list'
>  [00:12:10.544266 run-command.c:337] trace: run_command: 'git-stash' 'list'
>  [00:12:10.649779 git.c:312] trace: built-in: git 'rev-parse' '--git-dir'

This is easier to parse if " " and ":" are found in the names of
_our_ source files and "]" isn't, but is that really the case?

> Or print file:line at the end (but what about multi-line messages, such as packet-trace?):
>
>  > GIT_TRACE=1 git stash list
>  00:12:10.544266 trace: exec: 'git-stash' 'list' (git.c:512)

Somehow I find this a lot harder to read than the other two.

I am not commenting on the usefulness of the patch series (yet),
though.

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Re: [PATCH v5 09/11] trace: add high resolution timer function to debug performance issues

[Junio C Hamano]

Karsten Blees <karsten.blees@gmail.com> writes:

> Am 11.06.2014 10:01, schrieb Karsten Blees:
>> the epoch allows using the results (div 10e9) with other time-related APIs.
>
> s/10e9/1e9/

That replacement is fine but the "(div 1e9)" still wants to be
clarified.  What did you exactly mean by that?  If the result is
divided by 10^9 then it yields the number of seconds?

Thanks.

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Re: [PATCH v5 10/11] trace: add trace_performance facility to debug performance issues

[Junio C Hamano]

Karsten Blees <karsten.blees@gmail.com> writes:

> Simple use case (measure one code section):
>
>   uint64_t start = getnanotime();
>   /* code section to measure */
>   trace_performance_since(start, "foobar");
>
> Medium use case (measure consecutive code sections):
>
>   uint64_t start = getnanotime();
>   /* first code section to measure */
>   start = trace_performance_since(start, "first foobar");
>   /* second code section to measure */
>   trace_performance_since(start, "second foobar");
>
> Complex use case (measure repetitive code sections):
>
>   uint64_t t = 0;
>   for (;;) {
>     /* ignore */
>     t -= getnanotime();
>     /* code section to measure */
>     t += getnanotime();
>     /* ignore */
>   }
>   trace_performance(t, "frotz");

Hmph.  Even though trace_performance() makes an extra call to
getnanotime() in order to return, examples do not use the returned
value?  The second example is a good illustration why it makes sense
for trace_performance_since(), though.

> +static void trace_performance_vfl(const char *file, int line,
> +				      uint64_t nanos, const char *format,
> +				      va_list ap)
> +{

Just being curious, but what does "v" stand for?

The "_fl" suffix you gave to printf family made a lot of sense to
me, and I would have expected that this to be called with a "_flt"
suffix, meaning "we have file, line and then time as extra
parameters" or something.

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Re: [PATCH v5 09/11] trace: add high resolution timer function to debug performance issues

[Karsten Blees]

Am 17.06.2014 18:44, schrieb Junio C Hamano:
> Karsten Blees <karsten.blees@gmail.com> writes:
> 
>> Am 11.06.2014 10:01, schrieb Karsten Blees:
>>> the epoch allows using the results (div 10e9) with other time-related APIs.
>>
>> s/10e9/1e9/
> 
> That replacement is fine but the "(div 1e9)" still wants to be
> clarified.  What did you exactly mean by that?  If the result is
> divided by 10^9 then it yields the number of seconds?
> 
> Thanks.
> 

Div 10^9 yields a time_t. But as not all time-related APIs use time_t, perhaps its best to drop the "(div 1e9)" altogether. That the function returns nanoseconds should be clear enough. Will drop in the next round.

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Re: [PATCH v5 10/11] trace: add trace_performance facility to debug performance issues

[Karsten Blees]

Am 17.06.2014 19:11, schrieb Junio C Hamano:
> Karsten Blees <karsten.blees@gmail.com> writes:
> 
>> Simple use case (measure one code section):
>>
>>   uint64_t start = getnanotime();
>>   /* code section to measure */
>>   trace_performance_since(start, "foobar");
>>
>> Medium use case (measure consecutive code sections):
>>
>>   uint64_t start = getnanotime();
>>   /* first code section to measure */
>>   start = trace_performance_since(start, "first foobar");
>>   /* second code section to measure */
>>   trace_performance_since(start, "second foobar");
>>
>> Complex use case (measure repetitive code sections):
>>
>>   uint64_t t = 0;
>>   for (;;) {
>>     /* ignore */
>>     t -= getnanotime();
>>     /* code section to measure */
>>     t += getnanotime();
>>     /* ignore */
>>   }
>>   trace_performance(t, "frotz");
> 
> Hmph.  Even though trace_performance() makes an extra call to
> getnanotime() in order to return, examples do not use the returned
> value?  The second example is a good illustration why it makes sense
> for trace_performance_since(), though.
> 

Right, it makes no sense for trace_performance(), and for
trace_performance_since() only if followed by another 'measured' code
section. In that special case, I think it wouldn't hurt if you had to
write:

  uint64_t start = getnanotime();
  /* first code section to measure */
  trace_performance_since(start, "first foobar");

  start = getnanotime();
  /* second code section to measure */
  trace_performance_since(start, "second foobar");

So I guess I'll drop the return value (and the second example, which
is then redundant to the first).

>> +static void trace_performance_vfl(const char *file, int line,
>> +				      uint64_t nanos, const char *format,
>> +				      va_list ap)
>> +{
> 
> Just being curious, but what does "v" stand for?
> 

trace_performance_vfl(, va_list)
vs.
trace_performance_fl(, ...)

Will change to trace_performance_vprintf_fl()

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Re: [PATCH v5 00/11] add performance tracing facility

[Karsten Blees]

Am 12.06.2014 20:30, schrieb Junio C Hamano:
> Karsten Blees <karsten.blees@gmail.com> writes:
> 
>> Here's v5 of the performance tracing patch series, now including a bunch of cleanups and adding timestamp, file and line to all trace output.
>>
>> I'm particularly interested in feedback for the output format. As file names have different lengths, printing file:line as prefix results in unaligned output:
>>
>>  > GIT_TRACE=1 git stash list
>>  00:12:10.544266 git.c:512 trace: exec: 'git-stash' 'list'
>>  00:12:10.544266 run-command.c:337 trace: run_command: 'git-stash' 'list'
>>  00:12:10.649779 git.c:312 trace: built-in: git 'rev-parse' '--git-dir'
>>
>> We could add separators to make it easier to parse, e.g.:
>>
>>  > GIT_TRACE=1 git stash list
>>  [00:12:10.544266 git.c:512] trace: exec: 'git-stash' 'list'
>>  [00:12:10.544266 run-command.c:337] trace: run_command: 'git-stash' 'list'
>>  [00:12:10.649779 git.c:312] trace: built-in: git 'rev-parse' '--git-dir'
> 
> This is easier to parse if " " and ":" are found in the names of
> _our_ source files and "]" isn't, but is that really the case?
> 

By "parsing" I actually meant the HumanEye (tm) parser, not lex/yacc and
friends ("[]" just make nice recognizable separators).

However, I think it shouldn't be too complicated to properly align the output,
at least for the majority of 'short' file names in the git code base. E.g.:

00:12:10.544266 git.c:512                trace: exec: 'git-stash' 'list'
00:12:10.544266 run-command.c:337        trace: run_command: 'git-stash' 'list'
00:12:10.649779 git.c:312                trace: built-in: git 'rev-parse' '--git-dir'

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Re: [PATCH v5 10/11] trace: add trace_performance facility to debug performance issues

[Junio C Hamano]

Karsten Blees <karsten.blees@gmail.com> writes:

> Right, it makes no sense for trace_performance(), and for
> trace_performance_since() only if followed by another 'measured' code
> section. In that special case, I think it wouldn't hurt if you had to
> write:
>
>   uint64_t start = getnanotime();
>   /* first code section to measure */
>   trace_performance_since(start, "first foobar");
>
>   start = getnanotime();
>   /* second code section to measure */
>   trace_performance_since(start, "second foobar");
>
> So I guess I'll drop the return value (and the second example, which
> is then redundant to the first).

That also sounds OK to me.

>>> +static void trace_performance_vfl(const char *file, int line,
>>> +				      uint64_t nanos, const char *format,
>>> +				      va_list ap)
>>> +{
>> 
>> Just being curious, but what does "v" stand for?
>> 
>
> trace_performance_vfl(, va_list)
> vs.
> trace_performance_fl(, ...)
>
> Will change to trace_performance_vprintf_fl()

Ah, OK.  The name with 'vprintf' in it does sound better.

Thanks.

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Re: [PATCH v5 00/11] add performance tracing facility

[Duy Nguyen]

On Wed, Jun 11, 2014 at 2:55 PM, Karsten Blees <karsten.blees@gmail.com> wrote:
> Here's v5 of the performance tracing patch series, now including a bunch of cleanups and adding timestamp, file and line to all trace output.
>
> I'm particularly interested in feedback for the output format. As file names have different lengths, printing file:line as prefix results in unaligned output:
>
>  > GIT_TRACE=1 git stash list
>  00:12:10.544266 git.c:512 trace: exec: 'git-stash' 'list'
>  00:12:10.544266 run-command.c:337 trace: run_command: 'git-stash' 'list'
>  00:12:10.649779 git.c:312 trace: built-in: git 'rev-parse' '--git-dir'

Can I have an (build-time) option to show <function>:<line> instead of
<file>:<line>? I know it's not supported by all compilers, which may
make support a bit cumbersome..
-- 
Duy

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Re: [PATCH v5 00/11] add performance tracing facility

[Karsten Blees]

Am 25.06.2014 16:28, schrieb Duy Nguyen:
> On Wed, Jun 11, 2014 at 2:55 PM, Karsten Blees <karsten.blees@gmail.com> wrote:
>> Here's v5 of the performance tracing patch series, now including a bunch of cleanups and adding timestamp, file and line to all trace output.
>>
>> I'm particularly interested in feedback for the output format. As file names have different lengths, printing file:line as prefix results in unaligned output:
>>
>>  > GIT_TRACE=1 git stash list
>>  00:12:10.544266 git.c:512 trace: exec: 'git-stash' 'list'
>>  00:12:10.544266 run-command.c:337 trace: run_command: 'git-stash' 'list'
>>  00:12:10.649779 git.c:312 trace: built-in: git 'rev-parse' '--git-dir'
> 
> Can I have an (build-time) option to show <function>:<line> instead of
> <file>:<line>? I know it's not supported by all compilers, which may
> make support a bit cumbersome..
> 

Is this really useful? <file>:<line> is unique, but <function>:<line> is not. E.g. in case of "hash_name:47" you'd have to guess if its the one in attr.c or name-hash.c...

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Re: [PATCH v5 00/11] add performance tracing facility

[Duy Nguyen]

On Wed, Jun 25, 2014 at 9:49 PM, Karsten Blees <karsten.blees@gmail.com> wrote:
> Am 25.06.2014 16:28, schrieb Duy Nguyen:
>> On Wed, Jun 11, 2014 at 2:55 PM, Karsten Blees <karsten.blees@gmail.com> wrote:
>>> Here's v5 of the performance tracing patch series, now including a bunch of cleanups and adding timestamp, file and line to all trace output.
>>>
>>> I'm particularly interested in feedback for the output format. As file names have different lengths, printing file:line as prefix results in unaligned output:
>>>
>>>  > GIT_TRACE=1 git stash list
>>>  00:12:10.544266 git.c:512 trace: exec: 'git-stash' 'list'
>>>  00:12:10.544266 run-command.c:337 trace: run_command: 'git-stash' 'list'
>>>  00:12:10.649779 git.c:312 trace: built-in: git 'rev-parse' '--git-dir'
>>
>> Can I have an (build-time) option to show <function>:<line> instead of
>> <file>:<line>? I know it's not supported by all compilers, which may
>> make support a bit cumbersome..
>>
>
> Is this really useful? <file>:<line> is unique, but <function>:<line> is not. E.g. in case of "hash_name:47" you'd have to guess if its the one in attr.c or name-hash.c...

It depends on your view. If I'm tracing a certain operation, function
names let me know roughly what's going on without looking at the code
because all (or many of) the names and their purposes are already in
my mind. But for publishing the traces, then I agree <file>:<line> is
better.
-- 
Duy

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