On Tue, Dec 09, 2014 at 09:41:28PM -0800, Shawn Pearce wrote: > On Tue, Dec 9, 2014 at 4:37 PM, brian m. carlson > <sand...@crustytoothpaste.net> wrote: > > Most of the time is spent between the "Pushing to remote machine" and > > "Counting objects", running git pack-objects: > > > > git pack-objects --all-progress-implied --revs --stdout --thin > > --delta-base-offset --progress > > > > Unfortunately, -vvv doesn't provide any helpful output. I have some > > suspicions what's going on here, but no hard data. Where should I > > be looking to determine the bottleneck? > > My guess is the revision queue is struggling to insert 20,000 commits > that the remote side "has", are uninteresting, and should not be > transmitted. This queue insertion usually requires parsing the commit > object out of the local object store to get the commit timestamp, then > bubble sort inserting that commit into the queue.
I looked at this more in depth today and I found that the bottleneck is --thin. I tried git send-pack, which does not use --thin by default, which led me to further testing. A particular push went from 24 seconds with --thin to 4 seconds without. I agree that the large number of refs is at least part of the problem, because reducing the number of refs has a slight but noticeable impact. It's also the factor I can least control. I have a patch which allows per-remote configuration of whether to use thin packs (which I will send shortly), but I'm wondering if we can do better, especially since --thin is the default. It looks like --thin forces pack-objects to do its own lookup (essentially a rev-list) instead of using the values provided on stdin. -- brian m. carlson / brian with sandals: Houston, Texas, US +1 832 623 2791 | http://www.crustytoothpaste.net/~bmc | My opinion only OpenPGP: RSA v4 4096b: 88AC E9B2 9196 305B A994 7552 F1BA 225C 0223 B187
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