On 2019-11-08 22:21, Jeff King wrote: > On Fri, Nov 08, 2019 at 09:54:02PM +0100, Paul van Loon wrote: > >>>> $ git push -v origin 'refs/replace/*:refs/replace/*' >>>> Pushing to XXXX >>>> Enumerating objects: 2681, done. >>>> Counting objects: 100% (2681/2681), done. >>>> Delta compression using up to 8 threads >>>> Compressing objects: 100% (1965/1965), done. >>>> Writing objects: 100% (2582/2582), 1.96 MiB | 1024 bytes/s, done. >>>> Total 2582 (delta 95), reused 1446 (delta 58) >>>> remote: Resolving deltas: 100% (95/95), completed with 33 local objects. >>>> To XXXX >>>> * [new branch] refs/replace/XXXX -> refs/replace/XXXX >>> >>> Could you verify that refs/replace/XXXX (or one of its close ancestors) >>> was fetched by the "git fetch --all" command? "--all" fetches all >>> remotes, not all refs. >> >> No, it was not fetched. HOWEVER, the ONLY thing the replace commit (1 single object) does is point to an existing parent object. No other new objects are referenced. >> Those 'ancestor' objects were all fetched. > > Was it a parent object at the tip of a ref? No, it was a newly created replace object (created with git replace --edit) > > The push protocol, unlike the fetch protocol, doesn't expend any effort > to negotiate to find a common base. It just feeds the ref tips of the > receiver to pack-objects (which then does traverse down to a merge base, > but it can't always do so if the sender doesn't have all of the > objects). So this would be the opportunity for performance improvement I guess. > > It's hard to say more without having a reproducible case to look at. > > Some possible things to poke at: > > - record the stdin from the local push to the local pack-objects, > which shows which objects we're planning to send and which we're > claiming the other side has. That would help determine if the push > isn't feeding enough information to pack-objects, or if pack-objects > isn't trying hard enough to find the minimal set of objects > > There's not really an easy way to do this, but something like strace > might help. That's way above my Git expertise. > - try building reachability bitmaps (e.g., "git repack -adb") in the > local clone. When those are present, pack-objects will compute the > object set more thoroughly (because it can do so efficiently). > > I don't _think_ the fact that it's in refs/replace should matter to push > (in terms of what it feeds to pack-objects). But obviously another thing > to try is whether pushing to or from a different ref has any impact. I'll do some additional experiments > -Peff >
