| commit | bb514de356cfcfd314f7ac7ae1acfeede3fa4b1f | [log] [tgz] |
|---|---|---|
| author | Jeff King <peff@peff.net> | Wed Dec 18 12:25:45 2019 +0100 |
| committer | Junio C Hamano <gitster@pobox.com> | Thu Jan 23 10:51:50 2020 -0800 |
| tree | dc222189645405ee1eab03d9493a553bf6f33b34 | |
| parent | ff483026a9ab29d01b6142ea3b44f4ffd8acb8c2 [diff] |
pack-objects: improve partial packfile reuse The old code to reuse deltas from an existing packfile just tried to dump a whole segment of the pack verbatim. That's faster than the traditional way of actually adding objects to the packing list, but it didn't kick in very often. This new code is really going for a middle ground: do _some_ per-object work, but way less than we'd traditionally do. The general strategy of the new code is to make a bitmap of objects from the packfile we'll include, and then iterate over it, writing out each object exactly as it is in our on-disk pack, but _not_ adding it to our packlist (which costs memory, and increases the search space for deltas). One complication is that if we're omitting some objects, we can't set a delta against a base that we're not sending. So we have to check each object in try_partial_reuse() to make sure we have its delta. About performance, in the worst case we might have interleaved objects that we are sending or not sending, and we'd have as many chunks as objects. But in practice we send big chunks. For instance, packing torvalds/linux on GitHub servers now reused 6.5M objects, but only needed ~50k chunks. Helped-by: Jonathan Tan <jonathantanmy@google.com> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Christian Couder <chriscool@tuxfamily.org> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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