On Wed, Jun 17, 2020 at 05:24:27PM +0000, Derrick Stolee via GitGitGadget wrote: > It was recently [1] reported (and not-so-recently [2] reported) that "git > merge-base --is-ancestor" can be pretty slow. In fact, it is regularly > slower than "git branch --contains" or "git tag --contains", which are > answering a "harder" query. > > [1] https://lore.kernel.org/git/20200607195347.GA8232@xxxxxxxxxx/ > > [2] https://lore.kernel.org/git/87608bawoa.fsf@xxxxxxxxxxxxxxxxxxx/ > > The root cause is that the in_merge_base() implementation is skipping the > fast can_all_from_reach() implementation and using paint_down_to_common() > instead. Note that these are equivalent: a commit A is in the set of > merge-bases between A and B if and only if B can reach A. > > This fixes the issue, and makes the performance degradation reported by > Szeder a non-issue. > > Thanks, -Stolee > > Derrick Stolee (2): > commit-reach: create repo_is_descendant_of() > commit-reach: use fast logic in repo_in_merge_base > > commit-reach.c | 21 ++++++++++++++++++--- > 1 file changed, 18 insertions(+), 3 deletions(-) > > > base-commit: b3d7a52fac39193503a0b6728771d1bf6a161464 > Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-664%2Fderrickstolee%2Fmerge-base-is-ancestor-v1 > Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-664/derrickstolee/merge-base-is-ancestor-v1 > Pull-Request: https://github.com/gitgitgadget/git/pull/664 > -- > gitgitgadget Wow! Thanks for investigating through the issue and following up. The performance numbers speak for themselves. By applying this series on the commit-slab patch series, both are now just as fast (master: 0.048s, commit-slab: 0.050s). Regards Abhishek
