p0004: use test_perf

The perf test suite (more specifically: t/perf/aggregate.perl) requires
each test script to write test results into a file, otherwise it aborts
when aggregating.  Add actual performance tests with test_perf to allow
p0004 to be run together with other perf scripts.

Calibrate the value for the parameter --count based on the size of the
test repository, in order to get meaningful results with smaller repos
yet still be able to finish the script against huge ones without having
to wait for hours.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Acked-by: Jeff Hostetler <git@jeffhostetler.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/perf/p0004-lazy-init-name-hash.sh

@@ -18,4 +18,40 @@ test_expect_success 'multithreaded should be faster' '
 	test-lazy-init-name-hash --perf >out.perf
 '
 
+test_expect_success 'calibrate' '
+	entries=$(wc -l <out.single) &&
+
+	case $entries in
+	?) count=1000000 ;;
+	??) count=100000 ;;
+	???) count=10000 ;;
+	????) count=1000 ;;
+	?????) count=100 ;;
+	??????) count=10 ;;
+	*) count=1 ;;
+	esac &&
+	export count &&
+
+	case $entries in
+	1) entries_desc="1 entry" ;;
+	*) entries_desc="$entries entries" ;;
+	esac &&
+
+	case $count in
+	1) count_desc="1 round" ;;
+	*) count_desc="$count rounds" ;;
+	esac &&
+
+	desc="$entries_desc, $count_desc" &&
+	export desc
+'
+
+test_perf "single-threaded, $desc" "
+	test-lazy-init-name-hash --single --count=$count
+"
+
+test_perf "multi-threaded, $desc" "
+	test-lazy-init-name-hash --multi --count=$count
+"
+
 test_done