a6ca601cdf
In commit0bc2557951(upload-pack: skip parse-object re-hashing of "want" objects, 2022-09-06), we optimized the parse_object() calls for v2 "want" lines from the client so that they avoided parsing blobs, and so that they used the commit-graph rather than parsing commit objects from scratch. We should extend that to two other spots: 1. We parse "have" objects in the got_oid() function. These won't generally be non-commits (unlike "want" lines from a partial clone). But we still benefit from the use of the commit-graph. 2. For v0, the "want" lines are parsed in receive_needs(). These are also less likely to be non-commits because by default they have to be ref tips. There are config options you might set to allow non-tip objects, but you'd mostly do so to support partial clones, and clients recent enough to support partial clone will generally speak v2 anyway. So I don't expect this change to improve performance much for day-to-day operations. But both are possible denial-of-service vectors, where an attacker can waste our time by sending over a large number of objects to parse (of course we may waste even more time serving a pack to them, but we try as much as possible to optimize that in pack-objects; we should do what we can here in upload-pack, too). With this patch, running p5600 with GIT_TEST_PROTOCOL_VERSION=0 shows similar results to what we saw in0bc2557951(which ran with the v2 protocol by default). Here are the numbers for linux.git: Test HEAD^ HEAD ----------------------------------------------------------------------------- 5600.3: checkout of result 50.91(87.95+2.93) 41.75(79.00+3.18) -18.0% Or for a more extreme (and malicious) case, we can claim to "have" every blob in git.git over the v0 protocol: $ { echo "0032want $(git rev-parse HEAD)" printf 0000 git cat-file --batch-all-objects --batch-check='%(objectname) %(objecttype)' | perl -alne 'print "0032have $F[0]" if $F[1] eq "blob"' } >input $ time ./git.old upload-pack . <input >/dev/null real 0m52.951s user 0m51.633s sys 0m1.304s $ time ./git.new upload-pack . <input >/dev/null real 0m0.261s user 0m0.156s sys 0m0.105s (Note that these don't actually compute a pack because of the hacky protocol usage, so those numbers are representing the raw blob-parsing effort done by upload-pack). Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
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