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authorJeff King <peff@peff.net>2013-07-02 02:16:23 -0400
committerJunio C Hamano <gitster@pobox.com>2013-07-02 12:03:34 -0700
commit16445242edd7e90dc564b657043d2a5efca68cb0 (patch)
tree09c8c2ffe659d4c0776891fb2938b48f6982160d
parent534f0e0996c0a5a0bea5bae8ae088a80a929932b (diff)
downloadgit-16445242edd7e90dc564b657043d2a5efca68cb0.tar.gz
fetch-pack: avoid quadratic list insertion in mark_complete
We insert the commit pointed to by each ref one-by-one into the "complete" commit_list using insert_by_date. Because each insertion is O(n), we end up with O(n^2) behavior. This typically doesn't matter, because the number of refs is reasonably small. And even if there are a lot of refs, they often point to a smaller set of objects (in which case the optimization in commit ea5f220 keeps our "n" small). However, in pathological repositories (hundreds of thousands of refs, each pointing to a unique commit), this quadratic behavior can make a difference. Since we do not care about the list order until we have finished building it, we can simply keep it unsorted during the insertion phase, then sort it afterwards. On a repository like the one described above, this dropped the time to do a no-op fetch from 2.0s to 1.7s. On normal repositories, it probably does not matter at all, but it does not hurt to protect ourselves from pathological cases. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
-rw-r--r--fetch-pack.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/fetch-pack.c b/fetch-pack.c
index abe5ffbba5..4df8abd7c1 100644
--- a/fetch-pack.c
+++ b/fetch-pack.c
@@ -505,7 +505,7 @@ static int mark_complete(const char *refname, const unsigned char *sha1, int fla
struct commit *commit = (struct commit *)o;
if (!(commit->object.flags & COMPLETE)) {
commit->object.flags |= COMPLETE;
- commit_list_insert_by_date(commit, &complete);
+ commit_list_insert(commit, &complete);
}
}
return 0;
@@ -622,6 +622,7 @@ static int everything_local(struct fetch_pack_args *args,
if (!args->depth) {
for_each_ref(mark_complete, NULL);
for_each_alternate_ref(mark_alternate_complete, NULL);
+ commit_list_sort_by_date(&complete);
if (cutoff)
mark_recent_complete_commits(args, cutoff);
}