On 10/11/2019 2:12 AM, Jeff King wrote: > On Tue, Oct 08, 2019 at 11:37:39AM -0700, Jonathan Tan wrote: > >> When building the packfile to be sent, send_pack() is given a list of >> remote refs to be used as exclusions. For each ref, it first checks if >> the ref exists locally, and if it does, passes it with a "^" prefix to >> pack-objects. However, in a partial clone, the check may trigger a lazy >> fetch. >> >> The additional commit ancestry information obtained during such fetches >> may show that certain objects that would have been sent are already >> known to the server, resulting in a smaller pack being sent. But this is >> at the cost of fetching from many possibly unrelated refs, and the lazy >> fetches do not help at all in the typical case where the client is >> up-to-date with the upstream of the branch being pushed. >> >> Ensure that these lazy fetches do not occur. > > That makes sense. For similar reasons, should we be using > OBJECT_INFO_QUICK here? If the other side has a bunch of ref tips that > we don't have, we'll end up re-scanning the pack directory over and over > (which is _usually_ pretty quick, but can be slow if you have a lot of > packs locally). And it's OK if we racily miss out on an exclusion due to > somebody else repacking simultaneously. That's a good idea. We can hint to the object store that we don't expect misses to be due to a concurrent repack, so we don't want to reprepare pack-files. -Stolee
