From 0910e8cab828b53fd7188a93c0476cab0af81cdc Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Wed, 19 Oct 2005 00:01:01 -0700 Subject: [PATCH] Optimize common case of git-rev-list I took a look at webgit, and it looks like at least for the "projects" page, the most common operation ends up being basically git-rev-list --header --parents --max-count=1 HEAD Now, the thing is, the way "git-rev-list" works, it always keeps on popping the parents and parsing them in order to build the list of parents, and it turns out that even though we just want a single commit, git-rev-list will invariably look up _three_ generations of commits. It will parse: - the commit we want (it obviously needs this) - it's parent(s) as part of the "pop_most_recent_commit()" logic - it will then pop one of the parents before it notices that it doesn't need any more - and as part of popping the parent, it will parse the grandparent (again due to "pop_most_recent_commit()". Now, I've strace'd it, and it really is pretty efficient on the whole, but if things aren't nicely cached, and with long-latency IO, doing those two extra objects (at a minimum - if the parent is a merge it will be more) is just wasted time, and potentially a lot of it. So here's a quick special-case for the trivial case of "just one commit, and no date-limits or other special rules". Signed-off-by: Linus Torvalds Signed-off-by: Junio C Hamano --- rev-list.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/rev-list.c b/rev-list.c index c60aa72957..3a32e405a3 100644 --- a/rev-list.c +++ b/rev-list.c @@ -624,6 +624,11 @@ int main(int argc, char **argv) if (!merge_order) { sort_by_date(&list); + if (list && !limited && max_count == 1 && + !tag_objects && !tree_objects && !blob_objects) { + show_commit(list->item); + return 0; + } if (limited) list = limit_list(list); if (topo_order)