From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-3.6 required=3.0 tests=AWL,BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_HI,RP_MATCHES_RCVD shortcircuit=no autolearn=ham autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 4F3C320445 for ; Fri, 13 Oct 2017 14:20:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753720AbdJMOUI (ORCPT ); Fri, 13 Oct 2017 10:20:08 -0400 Received: from cloud.peff.net ([104.130.231.41]:52146 "HELO cloud.peff.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753415AbdJMOUH (ORCPT ); Fri, 13 Oct 2017 10:20:07 -0400 Received: (qmail 23244 invoked by uid 109); 13 Oct 2017 14:20:07 -0000 Received: from Unknown (HELO peff.net) (10.0.1.2) by cloud.peff.net (qpsmtpd/0.94) with SMTP; Fri, 13 Oct 2017 14:20:07 +0000 Authentication-Results: cloud.peff.net; auth=none Received: (qmail 25664 invoked by uid 111); 13 Oct 2017 14:20:09 -0000 Received: from sigill.intra.peff.net (HELO sigill.intra.peff.net) (10.0.0.7) by peff.net (qpsmtpd/0.94) with SMTP; Fri, 13 Oct 2017 10:20:09 -0400 Authentication-Results: peff.net; auth=none Received: by sigill.intra.peff.net (sSMTP sendmail emulation); Fri, 13 Oct 2017 10:20:05 -0400 Date: Fri, 13 Oct 2017 10:20:05 -0400 From: Jeff King To: Derrick Stolee Cc: Constantine , Junio C Hamano , Christian Couder , Mike Hommey , git Subject: Re: git-clone causes out of memory Message-ID: <20171013142004.ocxpdkkbcxpi52yv@sigill.intra.peff.net> References: <2f9b8856-dacc-768d-32c2-985f5f145ba7@yandex.ru> <20171013124456.qsbaol7txdgdb6wq@sigill.intra.peff.net> <20171013135058.q7vhufdtin42ddic@sigill.intra.peff.net> <53f98311-3c5f-9863-5f6c-bc4f25fad317@gmail.com> <20171013135636.o2vhktt7aqx6luuy@sigill.intra.peff.net> <20171013141018.62zvezivkkhloc5d@sigill.intra.peff.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20171013141018.62zvezivkkhloc5d@sigill.intra.peff.net> Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org On Fri, Oct 13, 2017 at 10:10:18AM -0400, Jeff King wrote: > Hmm. So this patch makes it go fast: > > diff --git a/revision.c b/revision.c > index d167223e69..b52ea4e9d8 100644 > --- a/revision.c > +++ b/revision.c > @@ -409,7 +409,7 @@ static void file_add_remove(struct diff_options *options, > int diff = addremove == '+' ? REV_TREE_NEW : REV_TREE_OLD; > > tree_difference |= diff; > - if (tree_difference == REV_TREE_DIFFERENT) > + if (tree_difference & REV_TREE_DIFFERENT) > DIFF_OPT_SET(options, HAS_CHANGES); > } > > > But that essentially makes the conditional a noop (since we know we set > either NEW or OLD above and DIFFERENT is the union of those flags). > > I'm not sure I understand why file_add_remove() would ever want to avoid > setting HAS_CHANGES (certainly its companion file_change() always does). > This goes back to Junio's dd47aa3133 (try-to-simplify-commit: use > diff-tree --quiet machinery., 2007-03-14). > > Maybe I am missing something, but AFAICT this was always buggy. But > since it only affects adds and deletes, maybe nobody noticed? I'm also > not sure if it only causes a slowdown, or if this could cause us to > erroneously mark something as TREESAME which isn't (I _do_ think people > would have noticed that). Answering my own question a little, there is a hint in the comment a few lines above: /* * The goal is to get REV_TREE_NEW as the result only if the * diff consists of all '+' (and no other changes), REV_TREE_OLD * if the whole diff is removal of old data, and otherwise * REV_TREE_DIFFERENT (of course if the trees are the same we * want REV_TREE_SAME). * That means that once we get to REV_TREE_DIFFERENT, we do not * have to look any further. */ So my patch above is breaking that. But it's not clear from that comment why we care about knowing the different between NEW, OLD, and DIFFERENT. Grepping around for REV_TREE_NEW and REV_TREE_OLD, I think the answer is in try_to_simplify_commit(): case REV_TREE_NEW: if (revs->remove_empty_trees && rev_same_tree_as_empty(revs, p)) { /* We are adding all the specified * paths from this parent, so the * history beyond this parent is not * interesting. Remove its parents * (they are grandparents for us). * IOW, we pretend this parent is a * "root" commit. */ if (parse_commit(p) < 0) die("cannot simplify commit %s (invalid %s)", oid_to_hex(&commit->object.oid), oid_to_hex(&p->object.oid)); p->parents = NULL; } /* fallthrough */ case REV_TREE_OLD: case REV_TREE_DIFFERENT: So when --remove-empty is not in effect (and it's not by default), we don't care about OLD vs NEW, and we should be able to optimize further. -Peff