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. 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. Derrick Stolee (6): 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.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 | 6 + t/helper/test-prio-queue.c | 10 +- t/t6600-test-reach.sh | 98 +++++++++++++++- 9 files changed, 361 insertions(+), 23 deletions(-) base-commit: 2d3b1c576c85b7f5db1f418907af00ab88e0c303 Published-As: https://github.com/gitgitgadget/git/releases/tags/pr-25%2Fderrickstolee%2Ftopo-order%2Fprogress-v2 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-25/derrickstolee/topo-order/progress-v2 Pull-Request: https://github.com/gitgitgadget/git/pull/25 Range-diff vs v1: 1: 5e55669f4d = 1: cc1ec4c270 prio-queue: add 'peek' operation 2: 9628396af1 = 2: 404c918608 test-reach: add run_three_modes method 3: 708b4550a1 = 3: 30dee58c61 test-reach: add rev-list tests 4: 908442417d ! 4: a74ae13d4e revision.c: begin refactoring --topo-order logic @@ -168,4 +168,4 @@ + struct topo_walk_info *topo_walk_info; }; - extern int ref_excluded(struct string_list *, const char *path); + int ref_excluded(struct string_list *, const char *path); 5: a7272f2799 ! 5: 0e64fc144c commit/revisions: bookkeeping before refactoring @@ -27,7 +27,7 @@ define_commit_slab(indegree_slab, int); -/* record author-date for each commit object */ --define_commit_slab(author_date_slab, unsigned long); +-define_commit_slab(author_date_slab, timestamp_t); - -static void record_author_date(struct author_date_slab *author_date, - struct commit *commit) 6: 73713bcbee ! 6: 3b185ac3b1 revision.c: refactor basic topo-order logic @@ -153,11 +153,11 @@ /* * object flag allocation: -- * revision.h: 0---------10 26 -+ * revision.h: 0---------10 26--28 - * fetch-pack.c: 0----5 +- * revision.h: 0---------10 2526 ++ * revision.h: 0---------10 25----28 + * fetch-pack.c: 01 + * negotiator/default.c: 2--5 * walker.c: 0-2 - * upload-pack.c: 4 11-----14 16-----19 @@ * builtin/show-branch.c: 0-------------------------------------------26 * builtin/unpack-objects.c: 2021 @@ -404,11 +404,11 @@ --- a/revision.h +++ b/revision.h @@ - #define PATCHSAME (1u<<9) - #define BOTTOM (1u<<10) + #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 ALL_REV_FLAGS (((1u<<11)-1) | TRACK_LINEAR) #define DECORATE_SHORT_REFS 1 + #define DECORATE_FULL_REFS 2 -- gitgitgadget
