On 6/14/2022 7:00 AM, kylezhao(赵柯宇) wrote: >> This is a known issue, I think you've found the same problem discussed in these past threads: >> >> https://lore.kernel.org/git/38b99459158a45b1bea09037f3dd092d@xxxxxxxxxxxxxxxxxxxxxxxx/ >> https://lore.kernel.org/git/87zhoz8b9o.fsf@xxxxxxxxxxxxxxxxxxx/ > > Thanks. > >> The latter one in particular has a lot of extra details. The former also >> has the suggestion of a per-push bitmap configuration as a workaround. >> >> As your numbers show it's still an issue today, but those threads should >> help you if you're looking to dig further into the root cause. >> >> Aside from the underlying root causes it would be very nice to fix the >> progress code in that area, i.e. we "stall" on "Enumerating objects", >> which is just a matter of us not having a separate progress bar for the >> very expensive bitmap work we're doing. > > It looks like optimizing the bitmap to solve the problem will be a long > process. This requires developers to have a deep understanding of the > algorithm. > > A per-push bitmap configuration as a workaround can't completely solve the > problem, but it works for me. After all, bitmap was not designed to optimize > git push. Most of time, git push is not been called as frequently as git fetch. I think the issue is that bitmaps are designed to support servers, which don't exactly use "git push" but instead use "git upload-pack" with a very different type of data (a lot of branches simultaneously from a large variety of bases). In general, clients that use "git push" don't generally have bitmaps, so this has not been a priority. For clients, it is faster to do a more focused object walk. See these commits and blog post for more details: * d5d2e93577 (revision: implement sparse algorithm, 2019-01-16) * 3d036eb0d2 (pack-objects: create pack.useSparse setting, 2019-01-16) * https://devblogs.microsoft.com/devops/exploring-new-frontiers-for-git-push-performance/ Hopefully that gives enough context as to why one would want to disable bitmaps for most "git push" operations. > The problem has been around for 3 years, has the community considered providing > a config like "push.useBitmap" to prevent git push using bitmap? It would be > appreciated if there is such a config, which can quickly solve my problem and > doesn't seem like a lot of work. I think this config would be a good idea, and I would even argue that we might want to set it to "false" by default. > If no one is interested in it, I can also try to submit a patch (although it > may be a bit slow since all I am new to the git community). We would welcome the contribution! I look forward to seeing it when you're ready. Thanks, -Stolee
