| commit | 4844812b9ec9bc6ffdc2da2c54d9146ff4c97d94 | [log] [tgz] |
|---|---|---|
| author | Abhishek Kumar <abhishekkumar8222@gmail.com> | Wed Jun 17 14:44:09 2020 +0530 |
| committer | Junio C Hamano <gitster@pobox.com> | Wed Jun 17 14:37:23 2020 -0700 |
| tree | b0df2ea1f12101e9ab2456820fc5b32a86db91ed | |
| parent | 6da43d937ca96d277556fa92c5a664fb1cbcc8ac [diff] |
commit-graph: introduce commit_graph_data_slab The struct commit is used in many contexts. However, members `generation` and `graph_pos` are only used for commit-graph related operations and otherwise waste memory. This wastage would have been more pronounced as we transition to generation number v2, which uses 64-bit generation number instead of current 32-bits. As they are often accessed together, let's introduce struct commit_graph_data and move them to a commit_graph_data slab. While the overall test suite runs just as fast as master, (series: 26m48s, master: 27m34s, faster by 2.87%), certain commands like `git merge-base --is-ancestor` were slowed by 40% as discovered by Szeder Gábor [1]. After minimizing commit-slab access, the slow down persists but is closer to 20%. Derrick Stolee believes the slow down is attributable to the underlying algorithm rather than the slowness of commit-slab access [2] and we will follow-up in a later series. [1]: https://lore.kernel.org/git/20200607195347.GA8232@szeder.dev/ [2]: https://lore.kernel.org/git/13db757a-9412-7f1e-805c-8a028c4ab2b1@gmail.com/ Signed-off-by: Abhishek Kumar <abhishekkumar8222@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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