[PATCH v3 2/2] test-core-checksum-index: core.checksumindex test helper

[git@jeffhostetler.com]

From: Jeff Hostetler <jeffhost@microsoft.com>

Created test helper to measure read_index() with and without
core.checksumindex set and report performance.

Signed-off-by: Jeff Hostetler <jeffhost@microsoft.com>
---
 Makefile                            |  1 +
 t/helper/.gitignore                 |  1 +
 t/helper/test-core-checksum-index.c | 77 +++++++++++++++++++++++++++++++++++++
 3 files changed, 79 insertions(+)
 create mode 100644 t/helper/test-core-checksum-index.c

diff --git a/Makefile b/Makefile
index 9ec6065..6049427 100644
--- a/Makefile
+++ b/Makefile
@@ -607,6 +607,7 @@ PROGRAMS += $(patsubst %.o,git-%$X,$(PROGRAM_OBJS))
 TEST_PROGRAMS_NEED_X += test-chmtime
 TEST_PROGRAMS_NEED_X += test-ctype
 TEST_PROGRAMS_NEED_X += test-config
+TEST_PROGRAMS_NEED_X += test-core-checksum-index
 TEST_PROGRAMS_NEED_X += test-date
 TEST_PROGRAMS_NEED_X += test-delta
 TEST_PROGRAMS_NEED_X += test-dump-cache-tree
diff --git a/t/helper/.gitignore b/t/helper/.gitignore
index d6e8b36..f651a6b 100644
--- a/t/helper/.gitignore
+++ b/t/helper/.gitignore
@@ -1,6 +1,7 @@
 /test-chmtime
 /test-ctype
 /test-config
+/test-core-checksum-index
 /test-date
 /test-delta
 /test-dump-cache-tree
diff --git a/t/helper/test-core-checksum-index.c b/t/helper/test-core-checksum-index.c
new file mode 100644
index 0000000..0452dc2
--- /dev/null
+++ b/t/helper/test-core-checksum-index.c
@@ -0,0 +1,77 @@
+#include "cache.h"
+#include "parse-options.h"
+
+uint64_t time_runs(int do_checksum, int count)
+{
+	uint64_t t0, t1;
+	uint64_t sum = 0;
+	uint64_t avg;
+	int i;
+
+	git_config_set_gently("core.checksumindex",
+		(do_checksum ? "true" : "false"));
+
+	for (i = 0; i < count; i++) {
+		t0 = getnanotime();
+		read_cache();
+		t1 = getnanotime();
+
+		sum += (t1 - t0);
+
+		printf("%f %d [cache_nr %d]\n",
+			   ((double)(t1 - t0))/1000000000,
+			   do_checksum,
+			   the_index.cache_nr);
+		fflush(stdout);
+
+		discard_cache();
+	}
+
+	avg = sum / count;
+	if (count > 1) {
+		printf("%f %d avg\n",
+			   (double)avg/1000000000,
+			   do_checksum);
+		fflush(stdout);
+	}
+
+	return avg;
+}
+
+int cmd_main(int argc, const char **argv)
+{
+	int original_do_checksum;
+	int count = 1;
+	const char *usage[] = {
+		"test-core-checksum-index",
+		NULL
+	};
+	struct option options[] = {
+		OPT_INTEGER('c', "count", &count, "number of passes"),
+		OPT_END(),
+	};
+	const char *prefix;
+	uint64_t avg_0, avg_1;
+
+	prefix = setup_git_directory();
+	argc = parse_options(argc, argv, prefix, options, usage, 0);
+
+	if (count < 1)
+		die("count must greater than zero");
+
+	/* throw away call to get the index in the disk cache */
+	read_cache();
+	discard_cache();
+
+	git_config_get_bool("core.checksumindex", &original_do_checksum);
+
+	avg_1 = time_runs(1, count);
+	avg_0 = time_runs(0, count);
+
+	git_config_set_gently("core.checksumindex",
+		((original_do_checksum) ? "true" : "false"));
+
+	if (avg_0 >= avg_1)
+		die("skipping index checksum verification did not help");
+	return 0;
+}
-- 
2.9.3