From: Victoria Dye <vdye@github.com>
Date: Thu, 10 Nov 2022 19:06:03 +0000 (+0000)
Subject: reset: use 'skip_cache_tree_update' option
X-Git-Tag: v2.39.0-rc0~23^2~2
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=0e47bca0f7592f8053ffcc530d8afa1d2e364563;p=thirdparty%2Fgit.git

reset: use 'skip_cache_tree_update' option

Enable the 'skip_cache_tree_update' option in the variants that call
'prime_cache_tree()' after 'unpack_trees()' (specifically, 'git reset
--mixed' and 'git reset --hard'). This avoids redundantly rebuilding the
cache tree in both 'cache_tree_update()' at the end of 'unpack_trees()' and
in 'prime_cache_tree()', resulting in a small (but consistent) performance
improvement. From the newly-added 'p7102-reset.sh' test:

Test                         before            after
--------------------------------------------------------------------
7102.1: reset --hard (...)   2.11(0.40+1.54)   1.97(0.38+1.47) -6.6%

Signed-off-by: Victoria Dye <vdye@github.com>
Signed-off-by: Taylor Blau <me@ttaylorr.com>
---

diff --git a/builtin/reset.c b/builtin/reset.c
index fdce6f8c85..ab02777482 100644
--- a/builtin/reset.c
+++ b/builtin/reset.c
@@ -73,9 +73,11 @@ static int reset_index(const char *ref, const struct object_id *oid, int reset_t
 	case HARD:
 		opts.update = 1;
 		opts.reset = UNPACK_RESET_OVERWRITE_UNTRACKED;
+		opts.skip_cache_tree_update = 1;
 		break;
 	case MIXED:
 		opts.reset = UNPACK_RESET_PROTECT_UNTRACKED;
+		opts.skip_cache_tree_update = 1;
 		/* but opts.update=0, so working tree not updated */
 		break;
 	default:
diff --git a/t/perf/p7102-reset.sh b/t/perf/p7102-reset.sh
new file mode 100755
index 0000000000..9b039e8691
--- /dev/null
+++ b/t/perf/p7102-reset.sh
@@ -0,0 +1,21 @@
+#!/bin/sh
+
+test_description='performance of reset'
+. ./perf-lib.sh
+
+test_perf_default_repo
+test_checkout_worktree
+
+test_perf 'reset --hard with change in tree' '
+	base=$(git rev-parse HEAD) &&
+	test_commit --no-tag A &&
+	new=$(git rev-parse HEAD) &&
+
+	for i in $(test_seq 10)
+	do
+		git reset --hard $new &&
+		git reset --hard $base || return $?
+	done
+'
+
+test_done