[PATCH v3 0/7] Use generation numbers for --topo-order
- From
Derrick Stolee via GitGitGadget <gitgitgadget@gmail.com>
- Date
- Sep 21, 2018, 17:39 UTC
- Message-ID
- <pull.25.v3.git.gitgitgadget@gmail.com>
- In-Reply-To
- <pull.25.v2.git.gitgitgadget@gmail.com>
This patch series performs a decently-sized refactoring of the revision-walk machinery. Well, "refactoring" is probably the wrong word, as I don't actually remove the old code. Instead, when we see certain options in the 'rev_info' struct, we redirect the commit-walk logic to a new set of methods that distribute the workload differently. By using generation numbers in the commit-graph, we can significantly improve 'git log --graph' commands (and the underlying 'git rev-list --topo-order').
On the Linux repository, I got the following performance results when comparing to the previous version with or without a commit-graph:
Test: git rev-list --topo-order -100 HEAD HEAD~1, no commit-graph: 6.80 s HEAD~1, w/ commit-graph: 0.77 s HEAD, w/ commit-graph: 0.02 s
Test: git rev-list --topo-order -100 HEAD -- tools HEAD~1, no commit-graph: 9.63 s HEAD~1, w/ commit-graph: 6.06 s HEAD, w/ commit-graph: 0.06 s
If you want to read this series but are unfamiliar with the commit-graph and generation numbers, then I recommend reading Documentation/technical/commit-graph.txt or a blob post [1] I wrote on the subject. In particular, the three-part walk described in "revision.c: refactor basic topo-order logic" is present (but underexplained) as an animated PNG [2].
Since revision.c is an incredibly important (and old) portion of the codebase -- and because there are so many orthogonal options in 'struct rev_info' -- I consider this submission to be "RFC quality". That is, I am not confident that I am not missing anything, or that my solution is the best it can be. I did merge this branch with ds/commit-graph-with-grafts and the "DO-NOT-MERGE: write and read commit-graph always" commit that computes a commit-graph with every 'git commit' command. The test suite passed with that change, available on GitHub [3]. To ensure that I cover at least the case I think are interesting, I added tests to t6600-test-reach.sh to verify the walks report the correct results for the three cases there (no commit-graph, full commit-graph, and a partial commit-graph so the walk starts at GENERATION_NUMBER_INFINITY).
One notable case that is not included in this series is the case of a history comparison such as 'git rev-list --topo-order A..B'. The existing code in limit_list() has ways to cut the walk short when all pending commits are UNINTERESTING. Since this code depends on commit_list instead of the prio_queue we are using here, I chose to leave it untouched for now. We can revisit it in a separate series later. Since handle_commit() turns on revs->limited when a commit is UNINTERESTING, we do not hit the new code in this case. Removing this 'revs->limited = 1;' line yields correct results, but the performance is worse.
This series was based on ds/reachable, but is now based on 'master' to not conflict with 182070 "commit: use timestamp_t for author_date_slab". There is a small conflict with md/filter-trees, because it renamed a flag in revisions.h in the line before I add new flags. Hopefully this conflict is not too difficult to resolve.
Changes in V3: I added a new patch that updates the tab-alignment for flags in revision.h before adding new ones (Thanks, Ævar!). Also, I squashed the recommended changes to run_three_modes and test_three_modes from Szeder and Junio. Thanks!
Thanks, -Stolee
[1] https://blogs.msdn.microsoft.com/devops/2018/07/09/supercharging-the-git-commit-graph-iii-generations/ Supercharging the Git Commit Graph III: Generations and Graph Algorithms
[2] https://msdnshared.blob.core.windows.net/media/2018/06/commit-graph-topo-order-b-a.png Animation showing three-part walk
[3] https://github.com/derrickstolee/git/tree/topo-order/testA branch containing this series along with commits to compute commit-graph in entire test suite.
Cc: avarab@gmail.comCc: szeder.dev@gmail.com
Derrick Stolee (7): prio-queue: add 'peek' operation test-reach: add run_three_modes method test-reach: add rev-list tests revision.c: begin refactoring --topo-order logic commit/revisions: bookkeeping before refactoring revision.h: add whitespace in flag definitions revision.c: refactor basic topo-order logic
commit.c | 11 +- commit.h | 8 ++ object.h | 4 +- prio-queue.c | 9 ++ prio-queue.h | 6 + revision.c | 232 ++++++++++++++++++++++++++++++++++++- revision.h | 34 +++--- t/helper/test-prio-queue.c | 10 +- t/t6600-test-reach.sh | 96 ++++++++++++++- 9 files changed, 374 insertions(+), 36 deletions(-)
base-commit: 2d3b1c576c85b7f5db1f418907af00ab88e0c303 Published-As: https://github.com/gitgitgadget/git/releases/tags/pr-25%2Fderrickstolee%2Ftopo-order%2Fprogress-v3 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-25/derrickstolee/topo-order/progress-v3 Pull-Request: https://github.com/gitgitgadget/git/pull/25
Range-diff vs v2:
1: cc1ec4c270 = 1: cc1ec4c270 prio-queue: add 'peek' operation
2: 404c918608 ! 2: b2a1ade148 test-reach: add run_three_modes method
@@ -11,10 +11,6 @@
run_three_modes method that executes the given command and tests
the actual output to the expected output.
- While inspecting this code, I realized that the final test for
- 'commit_contains --tag' is silently dropping the '--tag' argument.
- It should be quoted to include both.
-
Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
diff --git a/t/t6600-test-reach.sh b/t/t6600-test-reach.sh
@@ -28,31 +24,22 @@
+run_three_modes () {
test_when_finished rm -rf .git/objects/info/commit-graph &&
- test-tool reach $1 <input >actual &&
-+ $1 <input >actual &&
++ "$@" <input >actual &&
test_cmp expect actual &&
cp commit-graph-full .git/objects/info/commit-graph &&
- test-tool reach $1 <input >actual &&
-+ $1 <input >actual &&
++ "$@" <input >actual &&
test_cmp expect actual &&
cp commit-graph-half .git/objects/info/commit-graph &&
- test-tool reach $1 <input >actual &&
-+ $1 <input >actual &&
++ "$@" <input >actual &&
test_cmp expect actual
}
+test_three_modes () {
-+ run_three_modes "test-tool reach $1"
++ run_three_modes test-tool reach "$@"
+}
+
test_expect_success 'ref_newer:miss' '
cat >input <<-\EOF &&
A:commit-5-7
-@@
- EOF
- echo "commit_contains(_,A,X,_):1" >expect &&
- test_three_modes commit_contains &&
-- test_three_modes commit_contains --tag
-+ test_three_modes "commit_contains --tag"
- '
-
- test_expect_success 'commit_contains:miss' '
3: 30dee58c61 ! 3: b0ceb96076 test-reach: add rev-list tests
@@ -30,7 +30,7 @@
+ commit-6-2 commit-5-2 commit-4-2 commit-3-2 commit-2-2 commit-1-2 \
+ commit-6-1 commit-5-1 commit-4-1 commit-3-1 commit-2-1 commit-1-1 \
+ >expect &&
-+ run_three_modes "git rev-list --topo-order commit-6-6"
++ run_three_modes git rev-list --topo-order commit-6-6
+'
+
+test_expect_success 'rev-list: first-parent topo-order' '
@@ -42,7 +42,7 @@
+ commit-6-2 \
+ commit-6-1 commit-5-1 commit-4-1 commit-3-1 commit-2-1 commit-1-1 \
+ >expect &&
-+ run_three_modes "git rev-list --first-parent --topo-order commit-6-6"
++ run_three_modes git rev-list --first-parent --topo-order commit-6-6
+'
+
+test_expect_success 'rev-list: range topo-order' '
@@ -54,7 +54,7 @@
+ commit-6-2 commit-5-2 commit-4-2 \
+ commit-6-1 commit-5-1 commit-4-1 \
+ >expect &&
-+ run_three_modes "git rev-list --topo-order commit-3-3..commit-6-6"
++ run_three_modes git rev-list --topo-order commit-3-3..commit-6-6
+'
+
+test_expect_success 'rev-list: range topo-order' '
@@ -66,7 +66,7 @@
+ commit-6-2 commit-5-2 commit-4-2 \
+ commit-6-1 commit-5-1 commit-4-1 \
+ >expect &&
-+ run_three_modes "git rev-list --topo-order commit-3-8..commit-6-6"
++ run_three_modes git rev-list --topo-order commit-3-8..commit-6-6
+'
+
+test_expect_success 'rev-list: first-parent range topo-order' '
@@ -78,7 +78,7 @@
+ commit-6-2 \
+ commit-6-1 commit-5-1 commit-4-1 \
+ >expect &&
-+ run_three_modes "git rev-list --first-parent --topo-order commit-3-8..commit-6-6"
++ run_three_modes git rev-list --first-parent --topo-order commit-3-8..commit-6-6
+'
+
+test_expect_success 'rev-list: ancestry-path topo-order' '
@@ -88,7 +88,7 @@
+ commit-6-4 commit-5-4 commit-4-4 commit-3-4 \
+ commit-6-3 commit-5-3 commit-4-3 \
+ >expect &&
-+ run_three_modes "git rev-list --topo-order --ancestry-path commit-3-3..commit-6-6"
++ run_three_modes git rev-list --topo-order --ancestry-path commit-3-3..commit-6-6
+'
+
+test_expect_success 'rev-list: symmetric difference topo-order' '
@@ -102,7 +102,7 @@
+ commit-3-8 commit-2-8 commit-1-8 \
+ commit-3-7 commit-2-7 commit-1-7 \
+ >expect &&
-+ run_three_modes "git rev-list --topo-order commit-3-8...commit-6-6"
++ run_three_modes git rev-list --topo-order commit-3-8...commit-6-6
+'
+
test_done
4: a74ae13d4e = 4: fd1a0ab7cd revision.c: begin refactoring --topo-order logic
5: 0e64fc144c = 5: e86f304082 commit/revisions: bookkeeping before refactoring
-: ---------- > 6: fa6d5ef152 revision.h: add whitespace in flag definitions
6: 3b185ac3b1 ! 7: 020b2f50c5 revision.c: refactor basic topo-order logic
@@ -404,11 +404,11 @@
--- a/revision.h
+++ b/revision.h
@@
- #define USER_GIVEN (1u<<25) /* given directly by the user */
- #define TRACK_LINEAR (1u<<26)
- #define ALL_REV_FLAGS (((1u<<11)-1) | USER_GIVEN | TRACK_LINEAR)
-+#define TOPO_WALK_EXPLORED (1u<<27)
-+#define TOPO_WALK_INDEGREE (1u<<28)
+ #define USER_GIVEN (1u<<25) /* given directly by the user */
+ #define TRACK_LINEAR (1u<<26)
+ #define ALL_REV_FLAGS (((1u<<11)-1) | USER_GIVEN | TRACK_LINEAR)
++#define TOPO_WALK_EXPLORED (1u<<27)
++#define TOPO_WALK_INDEGREE (1u<<28)
#define DECORATE_SHORT_REFS 1
#define DECORATE_FULL_REFS 2-- gitgitgadget