[PATCH v3 1/9] trace.c: add GIT_TRACE_PACK_STATS for pack usage statistics

["Nguyễn Thái Ngọc Duy" <pclouds@gmail.com>]

trace_stats() is intended for GIT_TRACE_*_STATS variable group and
GIT_TRACE_PACK_STATS is more like an example how new vars can be added.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 Documentation/git.txt |  3 +++
 cache.h               |  2 ++
 git.c                 |  1 +
 sha1_file.c           | 24 ++++++++++++++++++++++++
 trace.c               | 13 +++++++++++++
 trace.h               |  1 +
 6 files changed, 44 insertions(+)

diff --git a/Documentation/git.txt b/Documentation/git.txt
index a0f1ede..a124612 100644
--- a/Documentation/git.txt
+++ b/Documentation/git.txt
@@ -946,6 +946,9 @@ Unsetting the variable, or setting it to empty, "0" or
 	time of each Git command.
 	See 'GIT_TRACE' for available trace output options.
 
+'GIT_TRACE_PACK_STATS'::
+	Print various statistics.
+
 'GIT_TRACE_SETUP'::
 	Enables trace messages printing the .git, working tree and current
 	working directory after Git has completed its setup phase.
diff --git a/cache.h b/cache.h
index fcb511d..1c84227 100644
--- a/cache.h
+++ b/cache.h
@@ -1502,4 +1502,6 @@ void stat_validity_update(struct stat_validity *sv, int fd);
 
 int versioncmp(const char *s1, const char *s2);
 
+void report_pack_stats(struct trace_key *key);
+
 #endif /* CACHE_H */
diff --git a/git.c b/git.c
index 9c49519..6a6a8a8 100644
--- a/git.c
+++ b/git.c
@@ -614,6 +614,7 @@ int main(int argc, char **av)
 	git_setup_gettext();
 
 	trace_command_performance(argv);
+	trace_stats();
 
 	/*
 	 * "git-xxxx" is the same as "git xxxx", but we obviously:
diff --git a/sha1_file.c b/sha1_file.c
index 3f70b1d..21a487b 100644
--- a/sha1_file.c
+++ b/sha1_file.c
@@ -467,6 +467,7 @@ static unsigned int peak_pack_open_windows;
 static unsigned int pack_open_windows;
 static unsigned int pack_open_fds;
 static unsigned int pack_max_fds;
+static unsigned int pack_access_nr;
 static size_t peak_pack_mapped;
 static size_t pack_mapped;
 struct packed_git *packed_git;
@@ -492,6 +493,28 @@ void pack_report(void)
 		sz_fmt(pack_mapped), sz_fmt(peak_pack_mapped));
 }
 
+void report_pack_stats(struct trace_key *key)
+{
+	trace_printf_key(key, "\n"
+			 "pack_report: getpagesize()            = %10" SZ_FMT "\n"
+			 "pack_report: core.packedGitWindowSize = %10" SZ_FMT "\n"
+			 "pack_report: core.packedGitLimit      = %10" SZ_FMT "\n"
+			 "pack_report: pack_used_ctr            = %10u\n"
+			 "pack_report: pack_mmap_calls          = %10u\n"
+			 "pack_report: pack_open_windows        = %10u / %10u\n"
+			 "pack_report: pack_mapped              = "
+			 "%10" SZ_FMT " / %10" SZ_FMT "\n"
+			 "pack_report: pack accesss             = %10u\n",
+			 sz_fmt(getpagesize()),
+			 sz_fmt(packed_git_window_size),
+			 sz_fmt(packed_git_limit),
+			 pack_used_ctr,
+			 pack_mmap_calls,
+			 pack_open_windows, peak_pack_open_windows,
+			 sz_fmt(pack_mapped), sz_fmt(peak_pack_mapped),
+			 pack_access_nr);
+}
+
 /*
  * Open and mmap the index file at path, perform a couple of
  * consistency checks, then record its information to p.  Return 0 on
@@ -2086,6 +2109,7 @@ static void write_pack_access_log(struct packed_git *p, off_t obj_offset)
 	static struct trace_key pack_access = TRACE_KEY_INIT(PACK_ACCESS);
 	trace_printf_key(&pack_access, "%s %"PRIuMAX"\n",
 			 p->pack_name, (uintmax_t)obj_offset);
+	pack_access_nr++;
 }
 
 int do_check_packed_object_crc;
diff --git a/trace.c b/trace.c
index e583dc6..c52da0f 100644
--- a/trace.c
+++ b/trace.c
@@ -426,3 +426,16 @@ void trace_command_performance(const char **argv)
 	sq_quote_argv(&command_line, argv, 0);
 	command_start_time = getnanotime();
 }
+
+static struct trace_key trace_pack_stats = TRACE_KEY_INIT(PACK_STATS);
+
+static void print_stats_atexit(void)
+{
+	report_pack_stats(&trace_pack_stats);
+}
+
+void trace_stats(void)
+{
+	if (trace_want(&trace_pack_stats))
+		atexit(print_stats_atexit);
+}
diff --git a/trace.h b/trace.h
index ae6a332..9c06e82 100644
--- a/trace.h
+++ b/trace.h
@@ -18,6 +18,7 @@ extern int trace_want(struct trace_key *key);
 extern void trace_disable(struct trace_key *key);
 extern uint64_t getnanotime(void);
 extern void trace_command_performance(const char **argv);
+extern void trace_stats(void);
 
 #ifndef HAVE_VARIADIC_MACROS
 
-- 
2.1.0.rc0.66.gb9187ad