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 <p...@peff.net> --- A note on the timings. I measured the times above last year when I wrote the same patch here: http://article.gmane.org/gmane.comp.version-control.git/194939 And earlier tonight, I did a fetch that showed the same result. But when I tried to replicate it while writing the commit message, I had trouble, because either: 1. I was fetching actual commits, in which case the more serious problem behavior in find_common kicked in, ruining the measurement. 2. It was a no-op fetch, in which case quickfetch() kicked in and we did not call mark_complete at all. So I'm rather confused how I managed to get timings earlier (both last year, and earlier today). But I still think it's an obviously correct thing to do, and does protect us in case (1) above (actually fetching a commit) once we fix the problem in find_common. fetch-pack.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fetch-pack.c b/fetch-pack.c index abe5ffb..4df8abd 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); } -- 1.8.3.rc2.14.g7eee6b3 -- To unsubscribe from this list: send the line "unsubscribe git" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
