On Wed, Mar 2, 2016 at 1:31 PM, Junio C Hamano <gitster@xxxxxxxxx> wrote: > Al Viro <viro@xxxxxxxxxxxxxxxxxx> writes: > >> FWIW, I wasn't proposing to recreate the remaining bits of that _pack_; >> just do the normal pull with one addition: start with sending the list >> of sha1 of objects you are about to send and let the recepient reply >> with "I already have <set of sha1>, don't bother with those". And exclude >> those from the transfer. > > I did a quick-and-dirty unscientific experiment. > > I had a clone of Linus's repository that was about a week old, whose > tip was at 4de8ebef (Merge tag 'trace-fixes-v4.5-rc5' of > git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace, > 2016-02-22). To bring it up to date (i.e. a pull about a week's > worth of progress) to f691b77b (Merge branch 'for-linus' of > git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs, 2016-03-01): > > $ git rev-list --objects 4de8ebef..f691b77b1fc | wc -l > 1396 > $ git rev-parse 4de8ebef..f691b77b1fc | > git pack-objects --revs --delta-base-offset --stdout | > wc -c > 2444127 > > So in order to salvage some transfer out of 2.4MB, the hypothetical > Al protocol would first have the upload-pack give 20*1396 = 28kB It could be 10*1396 or less. If the server calculates the shortest unambiguous SHA-1 length (quite cheap on fully packed repo) and sends it to the client, the client can just sends short SHA-1 instead. It's racy though because objects are being added to the server and abbrev length may go up. But we can check ambiguity for all SHA-1 sent by client and ask for resend for ambiguous ones. On my linux-2.6.git, 10 letters (so 5 bytes) are needed for unambiguous short SHA-1. But we can even go optimistic and ask the client for shorter SHA-1 with hope that resend won't be many. > object names to fetch-pack; no matter how fetch-pack encodes its > preference, its answer would be less than 28kB. We would likely to > design this part of the new protocol in line with the existing part > and use textual object names, so let's round them up to 100kB. -- Duy -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html