Re: [PATCH] sha1_name: cache readdir(3) results in find_short_object_filename()

["René Scharfe" <l.s.r@web.de>]

Am 23.06.2017 um 01:10 schrieb Jeff King:
> On Thu, Jun 22, 2017 at 08:19:48PM +0200, René Scharfe wrote:
> 
>> Read each loose object subdirectory at most once when looking for unique
>> abbreviated hashes.  This speeds up commands like "git log --pretty=%h"
>> considerably, which previously caused one readdir(3) call for each
>> candidate, even for subdirectories that were visited before.
> 
> Is it worth adding a perf test that's heavy on abbreviations?

Sure.  Here's a simple one.  It currently reports for me:

Test                        origin/master     origin/next              origin/pu
---------------------------------------------------------------------------------------------
4205.1: log with %H         0.44(0.41+0.02)   0.43(0.42+0.01) -2.3%    0.43(0.43+0.00) -2.3%
4205.2: log with %h         1.03(0.60+0.42)   1.04(0.64+0.39) +1.0%    0.57(0.55+0.01) -44.7%
4205.3: log with %T         0.43(0.42+0.00)   0.43(0.42+0.01) +0.0%    0.43(0.40+0.02) +0.0%
4205.4: log with %t         1.05(0.64+0.38)   1.05(0.61+0.42) +0.0%    0.59(0.58+0.00) -43.8%
4205.5: log with %P         0.45(0.42+0.02)   0.43(0.42+0.00) -4.4%    0.43(0.42+0.01) -4.4%
4205.6: log with %p         1.21(0.63+0.57)   1.17(0.68+0.47) -3.3%    0.59(0.58+0.00) -51.2%
4205.7: log with %h-%h-%h   1.05(0.64+0.39)   2.00(0.83+1.15) +90.5%   0.69(0.66+0.02) -34.3%

origin/next has fe9e2aefd4 (pretty: recalculate duplicate short hashes),
while origin/pu has cc817ca3ef (sha1_name: cache readdir(3) results in
find_short_object_filename()).

-- >8 --
Subject: [PATCH] p4205: add perf test script for pretty log formats

Add simple performance tests for expanded log format placeholders.

Suggested-by: Jeff King <peff@peff.net>
Signed-off-by: Rene Scharfe <l.s.r@web.de>
---
 t/perf/p4205-log-pretty-formats.sh | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)
 create mode 100755 t/perf/p4205-log-pretty-formats.sh

diff --git a/t/perf/p4205-log-pretty-formats.sh b/t/perf/p4205-log-pretty-formats.sh
new file mode 100755
index 0000000000..7c26f4f337
--- /dev/null
+++ b/t/perf/p4205-log-pretty-formats.sh
@@ -0,0 +1,16 @@
+#!/bin/sh
+
+test_description='Tests the performance of various pretty format placeholders'
+
+. ./perf-lib.sh
+
+test_perf_default_repo
+
+for format in %H %h %T %t %P %p %h-%h-%h
+do
+	test_perf "log with $format" "
+		git log --format=\"$format\" >/dev/null
+	"
+done
+
+test_done
-- 
2.13.1