From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Torvalds Subject: Re: git and larger trees, not so fast? Date: Fri, 10 Aug 2007 08:49:56 -0700 (PDT) Message-ID: References: <20070809163026.GD568@mbox.bz> <7vmyx0y3vp.fsf@assigned-by-dhcp.cox.net> <7v7io4xwvp.fsf@assigned-by-dhcp.cox.net> <20070809165218.9b76ebf7.seanlkml@sympatico.ca> <7vtzr8wemb.fsf@assigned-by-dhcp.cox.net> <7vps1wwa5w.fsf@assigned-by-dhcp.cox.net> <7vhcn8w6sw.fsf@assigned-by-dhcp.cox.net> <7v643ovyli.fsf@assigned-by-dhcp.cox.net> <7vy7gkue5s.fsf@assigned-by-dhcp.cox.net> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=us-ascii Cc: Sean , moe , git@vger.kernel.org To: Junio C Hamano X-From: git-owner@vger.kernel.org Fri Aug 10 17:50:53 2007 Return-path: Envelope-to: gcvg-git@gmane.org Received: from vger.kernel.org ([209.132.176.167]) by lo.gmane.org with esmtp (Exim 4.50) id 1IJWlE-0006mX-I4 for gcvg-git@gmane.org; Fri, 10 Aug 2007 17:50:48 +0200 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757745AbXHJPun (ORCPT ); Fri, 10 Aug 2007 11:50:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S936500AbXHJPun (ORCPT ); Fri, 10 Aug 2007 11:50:43 -0400 Received: from smtp2.linux-foundation.org ([207.189.120.14]:52964 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S937382AbXHJPuj (ORCPT ); Fri, 10 Aug 2007 11:50:39 -0400 Received: from imap1.linux-foundation.org (imap1.linux-foundation.org [207.189.120.55]) by smtp2.linux-foundation.org (8.13.5.20060308/8.13.5/Debian-3ubuntu1.1) with ESMTP id l7AFo2m2020065 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Fri, 10 Aug 2007 08:50:07 -0700 Received: from localhost (localhost [127.0.0.1]) by imap1.linux-foundation.org (8.13.5.20060308/8.13.5/Debian-3ubuntu1.1) with ESMTP id l7AFnuRr028674; Fri, 10 Aug 2007 08:49:56 -0700 In-Reply-To: <7vy7gkue5s.fsf@assigned-by-dhcp.cox.net> X-Spam-Status: No, hits=-2.724 required=5 tests=AWL,BAYES_00 X-Spam-Checker-Version: SpamAssassin 3.1.0-osdl_revision__1.20__ X-MIMEDefang-Filter: lf$Revision: 1.184 $ X-Scanned-By: MIMEDefang 2.53 on 207.189.120.14 Sender: git-owner@vger.kernel.org Precedence: bulk X-Mailing-List: git@vger.kernel.org Archived-At: On Thu, 9 Aug 2007, Junio C Hamano wrote: > > FWIW, moe's script with and without two patches gives these > numbers for me. Btw, I really think it's worth doing even just the hacky patches at this stage, even though it's late in the game for 1.5.3. That performance problem is serious enough that I'd call it a major bug. Performance has always been one of the goals of git, and when you have a difference between 17s and 0.7s for "git status", that's a *huge* usability thing. It would be sad to release 1.5.3 with a known bug. [ Some people don't think performance issues are "real bugs", and I think such people shouldn't be allowed to program. ] Side note: your first patch is actually quite noticeable on even just the kernel. Not nearly as much, but without it, I get about 0.5s, and with it, I get consistently under 0.3s. So it's about a 40% improvement even for smaller projects (and it's probably much more if you have a CPU with a smaller cache: my Core 2 Duo has 4MB of L2 cache, and a lot of the index will even fit in the L1 - a slower CPU with less cache will see a bigger impact, and with smaller repositories, from the unnecessary memory moving). While 0.5s -> 0.3s may not sound like much, on a slower machine where it might otherwise be 2.5s -> 1.5s, that's likely to be quite noticeable. In fact, I can tell even on my machine: 0.3s is visible as a "I'm clearly thinking about it" delay (quite frankly, it would be better at 0.1s, which is "immediate"), but 0.5s is already approaching the point where you actually wait for the answer (rather than just notice that it wasn't quite immediate). Linus