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From: "Abhishek Kumar via GitGitGadget" <gitgitgadget@gmail.com>
To: git@vger.kernel.org
Cc: "Derrick Stolee" <stolee@gmail.com>,
	"Jakub Narębski" <jnareb@gmail.com>,
	"Taylor Blau" <me@ttaylor.com>,
	"Abhishek Kumar" <abhishekkumar8222@gmail.com>,
	"Abhishek Kumar" <abhishekkumar8222@gmail.com>,
	"Abhishek Kumar" <abhishekkumar8222@gmail.com>
Subject: [PATCH v4 09/10] commit-reach: use corrected commit dates in paint_down_to_common()
Date: Wed, 07 Oct 2020 14:09:44 +0000
Message-ID: <bb9b02af32d028fc0c26d372aa490e260c74e74d.1602079786.git.gitgitgadget@gmail.com> (raw)
In-Reply-To: <pull.676.v4.git.1602079785.gitgitgadget@gmail.com>

From: Abhishek Kumar <abhishekkumar8222@gmail.com>

With corrected commit dates implemented, we no longer have to rely on
commit date as a heuristic in paint_down_to_common().

While using corrected commit dates Git walks nearly the same number of
commits as commit date, the process is slower as for each comparision we
have to access a commit-slab (for corrected committer date) instead of
accessing struct member (for committer date).

For example, the command `git merge-base v4.8 v4.9` on the linux
repository walks 167468 commits, taking 0.135s for committer date and
167496 commits, taking 0.157s for corrected committer date respectively.

t6404-recursive-merge setups a unique repository where all commits have
the same committer date without well-defined merge-base.

While running tests with GIT_TEST_COMMIT_GRAPH unset, we use committer
date as a heuristic in paint_down_to_common(). 6404.1 'combined merge
conflicts' merges commits in the order:
- Merge C with B to form a intermediate commit.
- Merge the intermediate commit with A.

With GIT_TEST_COMMIT_GRAPH=1, we write a commit-graph and subsequently
use the corrected committer date, which changes the order in which
commits are merged:
- Merge A with B to form a intermediate commit.
- Merge the intermediate commit with C.

While resulting repositories are equivalent, 6404.4 'virtual trees were
processed' fails with GIT_TEST_COMMIT_GRAPH=1 as we are selecting
different merge-bases and thus have different object ids for the
intermediate commits.

As this has already causes problems (as noted in 859fdc0 (commit-graph:
define GIT_TEST_COMMIT_GRAPH, 2018-08-29)), we disable commit graph
within t6404-recursive-merge.

Signed-off-by: Abhishek Kumar <abhishekkumar8222@gmail.com>
---
 commit-graph.c             | 14 ++++++++++++++
 commit-graph.h             |  8 +++++++-
 commit-reach.c             |  2 +-
 t/t6404-recursive-merge.sh |  5 ++++-
 4 files changed, 26 insertions(+), 3 deletions(-)

diff --git a/commit-graph.c b/commit-graph.c
index 5d15a1399b..3de1933ede 100644
--- a/commit-graph.c
+++ b/commit-graph.c
@@ -705,6 +705,20 @@ int generation_numbers_enabled(struct repository *r)
 	return !!first_generation;
 }
 
+int corrected_commit_dates_enabled(struct repository *r)
+{
+	struct commit_graph *g;
+	if (!prepare_commit_graph(r))
+		return 0;
+
+	g = r->objects->commit_graph;
+
+	if (!g->num_commits)
+		return 0;
+
+	return g->read_generation_data;
+}
+
 struct bloom_filter_settings *get_bloom_filter_settings(struct repository *r)
 {
 	struct commit_graph *g = r->objects->commit_graph;
diff --git a/commit-graph.h b/commit-graph.h
index ad52130883..d2c048dc64 100644
--- a/commit-graph.h
+++ b/commit-graph.h
@@ -89,13 +89,19 @@ struct commit_graph *read_commit_graph_one(struct repository *r,
 struct commit_graph *parse_commit_graph(struct repository *r,
 					void *graph_map, size_t graph_size);
 
+struct bloom_filter_settings *get_bloom_filter_settings(struct repository *r);
+
 /*
  * Return 1 if and only if the repository has a commit-graph
  * file and generation numbers are computed in that file.
  */
 int generation_numbers_enabled(struct repository *r);
 
-struct bloom_filter_settings *get_bloom_filter_settings(struct repository *r);
+/*
+ * Return 1 if and only if the repository has a commit-graph
+ * file and generation data chunk has been written for the file.
+ */
+int corrected_commit_dates_enabled(struct repository *r);
 
 enum commit_graph_write_flags {
 	COMMIT_GRAPH_WRITE_APPEND     = (1 << 0),
diff --git a/commit-reach.c b/commit-reach.c
index 20b48b872b..46f5a9e638 100644
--- a/commit-reach.c
+++ b/commit-reach.c
@@ -39,7 +39,7 @@ static struct commit_list *paint_down_to_common(struct repository *r,
 	int i;
 	timestamp_t last_gen = GENERATION_NUMBER_INFINITY;
 
-	if (!min_generation)
+	if (!min_generation && !corrected_commit_dates_enabled(r))
 		queue.compare = compare_commits_by_commit_date;
 
 	one->object.flags |= PARENT1;
diff --git a/t/t6404-recursive-merge.sh b/t/t6404-recursive-merge.sh
index 332cfc53fd..7055771b62 100755
--- a/t/t6404-recursive-merge.sh
+++ b/t/t6404-recursive-merge.sh
@@ -15,6 +15,8 @@ GIT_COMMITTER_DATE="2006-12-12 23:28:00 +0100"
 export GIT_COMMITTER_DATE
 
 test_expect_success 'setup tests' '
+	GIT_TEST_COMMIT_GRAPH=0 &&
+	export GIT_TEST_COMMIT_GRAPH &&
 	echo 1 >a1 &&
 	git add a1 &&
 	GIT_AUTHOR_DATE="2006-12-12 23:00:00" git commit -m 1 a1 &&
@@ -66,7 +68,7 @@ test_expect_success 'setup tests' '
 '
 
 test_expect_success 'combined merge conflicts' '
-	test_must_fail env GIT_TEST_COMMIT_GRAPH=0 git merge -m final G
+	test_must_fail git merge -m final G
 '
 
 test_expect_success 'result contains a conflict' '
@@ -82,6 +84,7 @@ test_expect_success 'result contains a conflict' '
 '
 
 test_expect_success 'virtual trees were processed' '
+	# TODO: fragile test, relies on ambigious merge-base resolution
 	git ls-files --stage >out &&
 
 	cat >expect <<-EOF &&
-- 
gitgitgadget


  parent reply index

Thread overview: 153+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-28  9:13 [PATCH 0/6] [GSoC] Implement Corrected Commit Date Abhishek Kumar via GitGitGadget
2020-07-28  9:13 ` [PATCH 1/6] commit-graph: fix regression when computing bloom filter Abhishek Kumar via GitGitGadget
2020-07-28 15:28   ` Taylor Blau
2020-07-30  5:24     ` Abhishek Kumar
2020-08-04  0:46   ` Jakub Narębski
2020-08-04  0:56     ` Taylor Blau
2020-08-04 10:10       ` Jakub Narębski
2020-08-04  7:55     ` Jakub Narębski
2020-07-28  9:13 ` [PATCH 2/6] revision: parse parent in indegree_walk_step() Abhishek Kumar via GitGitGadget
2020-07-28 13:00   ` Derrick Stolee
2020-07-28 15:30     ` Taylor Blau
2020-08-05 23:16   ` Jakub Narębski
2020-07-28  9:13 ` [PATCH 3/6] commit-graph: consolidate fill_commit_graph_info Abhishek Kumar via GitGitGadget
2020-07-28 13:14   ` Derrick Stolee
2020-07-28 15:19     ` René Scharfe
2020-07-28 15:58       ` Derrick Stolee
2020-07-28 16:01     ` Taylor Blau
2020-07-30  6:07     ` Abhishek Kumar
2020-07-28  9:13 ` [PATCH 4/6] commit-graph: consolidate compare_commits_by_gen Abhishek Kumar via GitGitGadget
2020-07-28 16:03   ` Taylor Blau
2020-07-28  9:13 ` [PATCH 5/6] commit-graph: implement generation data chunk Abhishek Kumar via GitGitGadget
2020-07-28 16:12   ` Taylor Blau
2020-07-30  6:52     ` Abhishek Kumar
2020-07-28  9:13 ` [PATCH 6/6] commit-graph: implement corrected commit date offset Abhishek Kumar via GitGitGadget
2020-07-28 15:55   ` Derrick Stolee
2020-07-28 16:23     ` Taylor Blau
2020-07-30  7:27     ` Abhishek Kumar
2020-07-28 14:54 ` [PATCH 0/6] [GSoC] Implement Corrected Commit Date Taylor Blau
2020-07-30  7:47   ` Abhishek Kumar
2020-07-28 16:35 ` Derrick Stolee
2020-08-09  2:53 ` [PATCH v2 00/10] " Abhishek Kumar via GitGitGadget
2020-08-09  2:53   ` [PATCH v2 01/10] commit-graph: fix regression when computing bloom filter Abhishek Kumar via GitGitGadget
2020-08-09  2:53   ` [PATCH v2 02/10] revision: parse parent in indegree_walk_step() Abhishek Kumar via GitGitGadget
2020-08-09  2:53   ` [PATCH v2 03/10] commit-graph: consolidate fill_commit_graph_info Abhishek Kumar via GitGitGadget
2020-08-09  2:53   ` [PATCH v2 04/10] commit-graph: consolidate compare_commits_by_gen Abhishek Kumar via GitGitGadget
2020-08-09  2:53   ` [PATCH v2 05/10] commit-graph: implement generation data chunk Abhishek Kumar via GitGitGadget
2020-08-10 16:28     ` Derrick Stolee
2020-08-11 11:03       ` Abhishek Kumar
2020-08-11 12:27         ` Derrick Stolee
2020-08-11 18:58           ` Taylor Blau
2020-08-09  2:53   ` [PATCH v2 06/10] commit-graph: return 64-bit generation number Abhishek Kumar via GitGitGadget
2020-08-09  2:53   ` [PATCH v2 07/10] commit-graph: implement corrected commit date Abhishek Kumar via GitGitGadget
2020-08-10 14:23     ` Derrick Stolee
2020-08-14  4:59       ` Abhishek Kumar
2020-08-14 12:24         ` Derrick Stolee
2020-08-09  2:53   ` [PATCH v2 08/10] commit-graph: handle mixed generation commit chains Abhishek Kumar via GitGitGadget
2020-08-10 16:42     ` Derrick Stolee
2020-08-11 11:36       ` Abhishek Kumar
2020-08-11 12:43         ` Derrick Stolee
2020-08-09  2:53   ` [PATCH v2 09/10] commit-reach: use corrected commit dates in paint_down_to_common() Abhishek Kumar via GitGitGadget
2020-08-09  2:53   ` [PATCH v2 10/10] doc: add corrected commit date info Abhishek Kumar via GitGitGadget
2020-08-10 16:47   ` [PATCH v2 00/10] [GSoC] Implement Corrected Commit Date Derrick Stolee
2020-08-15 16:39   ` [PATCH v3 00/11] " Abhishek Kumar via GitGitGadget
2020-08-15 16:39     ` [PATCH v3 01/11] commit-graph: fix regression when computing bloom filter Abhishek Kumar via GitGitGadget
2020-08-17 22:30       ` Jakub Narębski
2020-08-15 16:39     ` [PATCH v3 02/11] revision: parse parent in indegree_walk_step() Abhishek Kumar via GitGitGadget
2020-08-18 14:18       ` Jakub Narębski
2020-08-15 16:39     ` [PATCH v3 03/11] commit-graph: consolidate fill_commit_graph_info Abhishek Kumar via GitGitGadget
2020-08-19 17:54       ` Jakub Narębski
2020-08-21  4:11         ` Abhishek Kumar
2020-08-25 11:11           ` Jakub Narębski
2020-09-01 11:35             ` Abhishek Kumar
2020-08-15 16:39     ` [PATCH v3 04/11] commit-graph: consolidate compare_commits_by_gen Abhishek Kumar via GitGitGadget
2020-08-17 13:22       ` Derrick Stolee
2020-08-21 11:05       ` Jakub Narębski
2020-08-15 16:39     ` [PATCH v3 05/11] commit-graph: return 64-bit generation number Abhishek Kumar via GitGitGadget
2020-08-21 13:14       ` Jakub Narębski
2020-08-25  5:04         ` Abhishek Kumar
2020-08-25 12:18           ` Jakub Narębski
2020-09-01 12:06             ` Abhishek Kumar
2020-09-03 13:42               ` Jakub Narębski
2020-09-05 17:21                 ` Abhishek Kumar
2020-09-13 15:39                   ` Jakub Narębski
2020-09-28 21:48                     ` Jakub Narębski
2020-10-05  5:25                       ` Abhishek Kumar
2020-08-15 16:39     ` [PATCH v3 06/11] commit-graph: add a slab to store topological levels Abhishek Kumar via GitGitGadget
2020-08-21 18:43       ` Jakub Narębski
2020-08-25  6:14         ` Abhishek Kumar
2020-08-25  7:33           ` Jakub Narębski
2020-08-25  7:56             ` Jakub Narębski
2020-09-01 10:26               ` Abhishek Kumar
2020-09-03  9:25                 ` Jakub Narębski
2020-08-15 16:39     ` [PATCH v3 07/11] commit-graph: implement corrected commit date Abhishek Kumar via GitGitGadget
2020-08-22  0:05       ` Jakub Narębski
2020-08-25  6:49         ` Abhishek Kumar
2020-08-25 10:07           ` Jakub Narębski
2020-09-01 11:01             ` Abhishek Kumar
2020-08-15 16:39     ` [PATCH v3 08/11] commit-graph: implement generation data chunk Abhishek Kumar via GitGitGadget
2020-08-22 13:09       ` Jakub Narębski
2020-08-15 16:39     ` [PATCH v3 09/11] commit-graph: use generation v2 only if entire chain does Abhishek Kumar via GitGitGadget
2020-08-22 17:14       ` Jakub Narębski
2020-08-26  7:15         ` Abhishek Kumar
2020-08-26 10:38           ` Jakub Narębski
2020-08-15 16:39     ` [PATCH v3 10/11] commit-reach: use corrected commit dates in paint_down_to_common() Abhishek Kumar via GitGitGadget
2020-08-22 19:09       ` Jakub Narębski
2020-09-01 10:08         ` Abhishek Kumar
2020-09-03 19:11           ` Jakub Narębski
2020-08-15 16:39     ` [PATCH v3 11/11] doc: add corrected commit date info Abhishek Kumar via GitGitGadget
2020-08-22 22:20       ` Jakub Narębski
2020-08-27  6:39         ` Abhishek Kumar
2020-08-27 12:43           ` Jakub Narębski
2020-08-27 13:15           ` Derrick Stolee
2020-09-01 13:01             ` Abhishek Kumar
2020-08-17  0:13     ` [PATCH v3 00/11] [GSoC] Implement Corrected Commit Date Jakub Narębski
     [not found]       ` <CANQwDwdKp7oKy9BeKdvKhwPUiq0R5MS8TCw-eWGCYCoMGv=G-g@mail.gmail.com>
2020-08-17  1:32         ` Fwd: " Taylor Blau
2020-08-17  7:56           ` Jakub Narębski
2020-08-18  6:12       ` Abhishek Kumar
2020-08-23 15:27       ` Jakub Narębski
2020-08-24  2:49         ` Abhishek Kumar
2020-10-07 14:09     ` [PATCH v4 00/10] " Abhishek Kumar via GitGitGadget
2020-10-07 14:09       ` [PATCH v4 01/10] commit-graph: fix regression when computing Bloom filters Abhishek Kumar via GitGitGadget
2020-10-24 23:16         ` Jakub Narębski
2020-10-25 20:58           ` Taylor Blau
2020-11-03  5:36             ` Abhishek Kumar
2020-10-07 14:09       ` [PATCH v4 02/10] revision: parse parent in indegree_walk_step() Abhishek Kumar via GitGitGadget
2020-10-24 23:41         ` Jakub Narębski
2020-10-07 14:09       ` [PATCH v4 03/10] commit-graph: consolidate fill_commit_graph_info Abhishek Kumar via GitGitGadget
2020-10-25 10:52         ` Jakub Narębski
2020-10-27  6:33           ` Abhishek Kumar
2020-10-07 14:09       ` [PATCH v4 04/10] commit-graph: return 64-bit generation number Abhishek Kumar via GitGitGadget
2020-10-25 13:48         ` Jakub Narębski
2020-11-03  6:40           ` Abhishek Kumar
2020-10-07 14:09       ` [PATCH v4 05/10] commit-graph: add a slab to store topological levels Abhishek Kumar via GitGitGadget
2020-10-25 22:17         ` Jakub Narębski
2020-10-07 14:09       ` [PATCH v4 06/10] commit-graph: implement corrected commit date Abhishek Kumar via GitGitGadget
2020-10-27 18:53         ` Jakub Narębski
2020-11-03 11:44           ` Abhishek Kumar
2020-11-04 16:45             ` Jakub Narębski
2020-11-05 14:05               ` Philip Oakley
2020-11-05 18:22                 ` Junio C Hamano
2020-11-06 18:26                   ` Extending and updating gitglossary (was: Re: [PATCH v4 06/10] commit-graph: implement corrected commit date) Jakub Narębski
2020-11-06 19:33                     ` Extending and updating gitglossary Junio C Hamano
2020-11-08 17:23                     ` Extending and updating gitglossary (was: Re: [PATCH v4 06/10] commit-graph: implement corrected commit date) Philip Oakley
2020-11-10  1:35                       ` Extending and updating gitglossary Jakub Narębski
2020-11-10 14:04                         ` Philip Oakley
2020-11-10 23:52                           ` Jakub Narębski
2020-10-07 14:09       ` [PATCH v4 07/10] commit-graph: implement generation data chunk Abhishek Kumar via GitGitGadget
2020-10-30 12:45         ` Jakub Narębski
2020-11-06 11:25           ` Abhishek Kumar
2020-11-06 17:56             ` Jakub Narębski
2020-10-07 14:09       ` [PATCH v4 08/10] commit-graph: use generation v2 only if entire chain does Abhishek Kumar via GitGitGadget
2020-11-01  0:55         ` Jakub Narębski
2020-11-12 10:01           ` Abhishek Kumar
2020-11-13  9:59             ` Jakub Narębski
2020-10-07 14:09       ` Abhishek Kumar via GitGitGadget [this message]
2020-11-03 17:59         ` [PATCH v4 09/10] commit-reach: use corrected commit dates in paint_down_to_common() Jakub Narębski
2020-11-03 18:19           ` Junio C Hamano
2020-11-20 10:33           ` Abhishek Kumar
2020-10-07 14:09       ` [PATCH v4 10/10] doc: add corrected commit date info Abhishek Kumar via GitGitGadget
2020-11-04  1:37         ` Jakub Narębski
2020-11-21  6:30           ` Abhishek Kumar
2020-11-04 23:37       ` [PATCH v4 00/10] [GSoC] Implement Corrected Commit Date Jakub Narębski
2020-11-22  5:31         ` Abhishek Kumar

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