From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Shawn O. Pearce" Subject: [PATCH 11/11] Improve merge performance by avoiding in-index merges. Date: Thu, 28 Dec 2006 02:35:34 -0500 Message-ID: <20061228073534.GK17867@spearce.org> References: <9847899e4ba836980dbfed6d0ea1c82f31f21456.1167290864.git.spearce@spearce.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: git@vger.kernel.org X-From: git-owner@vger.kernel.org Thu Dec 28 08:35:47 2006 Return-path: Envelope-to: gcvg-git@gmane.org Received: from vger.kernel.org ([209.132.176.167]) by dough.gmane.org with esmtp (Exim 4.50) id 1Gzpnl-0000za-Ui for gcvg-git@gmane.org; Thu, 28 Dec 2006 08:35:46 +0100 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964996AbWL1Hfm (ORCPT ); Thu, 28 Dec 2006 02:35:42 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964998AbWL1Hfm (ORCPT ); Thu, 28 Dec 2006 02:35:42 -0500 Received: from corvette.plexpod.net ([64.38.20.226]:45856 "EHLO corvette.plexpod.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S964996AbWL1Hfl (ORCPT ); Thu, 28 Dec 2006 02:35:41 -0500 Received: from cpe-74-70-48-173.nycap.res.rr.com ([74.70.48.173] helo=asimov.home.spearce.org) by corvette.plexpod.net with esmtpa (Exim 4.52) id 1GzpnA-0007zH-Mw; Thu, 28 Dec 2006 02:35:12 -0500 Received: by asimov.home.spearce.org (Postfix, from userid 1000) id 0DD6320FB65; Thu, 28 Dec 2006 02:35:34 -0500 (EST) To: Junio C Hamano Content-Disposition: inline In-Reply-To: <9847899e4ba836980dbfed6d0ea1c82f31f21456.1167290864.git.spearce@spearce.org> User-Agent: Mutt/1.5.11 X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - corvette.plexpod.net X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [0 0] / [47 12] X-AntiAbuse: Sender Address Domain - spearce.org X-Source: X-Source-Args: X-Source-Dir: Sender: git-owner@vger.kernel.org Precedence: bulk X-Mailing-List: git@vger.kernel.org Archived-At: In the early days of Git we performed a 3-way read-tree based merge before attempting any specific merge strategy, as our core merge strategies of merge-one-file and merge-recursive were slower script based programs which took far longer to execute. This was a good performance optimization in the past, as most merges were able to be handled strictly by `read-tree -m -u`. However now that merge-recursive is a C based program which performs a full 3-way read-tree before it starts running we need to pay the cost of the 3-way read-tree twice if we have to do any sort of file level merging. This slows down some classes of simple merges which `read-tree -m -u` could not handle but which merge-recursive does automatically. For a really trivial merge which can be handled entirely by `read-tree -m -u`, skipping the read-tree and just going directly into merge-recursive saves on average 50 ms on my PowerPC G4 system. May sound odd, but it does appear to be true. In a really simple merge which needs to use merge-recursive to handle a file that was modified on both branches, skipping the read-tree in git-merge saves on average almost 100 ms (on the same PowerPC G4) as we avoid doing some work twice. We only avoid `read-tree -m -u` if the only strategy to use is merge-recursive, as not all merge strategies perform as well as merge-recursive does. Signed-off-by: Shawn O. Pearce --- git-merge.sh | 39 ++++++++++++++++++++++----------------- 1 files changed, 22 insertions(+), 17 deletions(-) diff --git a/git-merge.sh b/git-merge.sh index a8f673e..74d4fb0 100755 --- a/git-merge.sh +++ b/git-merge.sh @@ -341,23 +341,28 @@ f,*) ?,1,*,) # We are not doing octopus, not fast forward, and have only # one common. See if it is really trivial. - git var GIT_COMMITTER_IDENT >/dev/null || exit - - echo "Trying really trivial in-index merge..." - git-update-index --refresh 2>/dev/null - if git-read-tree --trivial -m -u -v $common $head "$1" && - result_tree=$(git-write-tree) - then - echo "Wonderful." - result_commit=$( - echo "$merge_msg" | - git-commit-tree $result_tree -p HEAD -p "$1" - ) || exit - finish "$result_commit" "In-index merge" - dropsave - exit 0 - fi - echo "Nope." + case "$use_strategies" in + recursive|'recursive '|recur|'recur ') + : run merge later + ;; + *) + git var GIT_COMMITTER_IDENT >/dev/null || exit + echo "Trying really trivial in-index merge..." + git-update-index --refresh 2>/dev/null + if git-read-tree --trivial -m -u -v $common $head "$1" && + result_tree=$(git-write-tree) + then + echo "Wonderful." + result_commit=$( + echo "$merge_msg" | + git-commit-tree $result_tree -p HEAD -p "$1" + ) || exit + finish "$result_commit" "In-index merge" + dropsave + exit 0 + fi + echo "Nope." + esac ;; *) # An octopus. If we can reach all the remote we are up to date. -- 1.4.4.3.gd2e4