From mboxrd@z Thu Jan 1 00:00:00 1970 From: Linus Torvalds Subject: Re: What's in git.git Date: Tue, 17 Oct 2006 10:16:21 -0700 (PDT) Message-ID: References: <7vvemjmlo2.fsf@assigned-by-dhcp.cox.net> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: git@vger.kernel.org X-From: git-owner@vger.kernel.org Tue Oct 17 19:17:05 2006 Return-path: Envelope-to: gcvg-git@gmane.org Received: from vger.kernel.org ([209.132.176.167]) by ciao.gmane.org with esmtp (Exim 4.43) id 1GZsYZ-0006N1-0G for gcvg-git@gmane.org; Tue, 17 Oct 2006 19:16:48 +0200 Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751323AbWJQRQn (ORCPT ); Tue, 17 Oct 2006 13:16:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751333AbWJQRQn (ORCPT ); Tue, 17 Oct 2006 13:16:43 -0400 Received: from smtp.osdl.org ([65.172.181.4]:51126 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S1751323AbWJQRQm (ORCPT ); Tue, 17 Oct 2006 13:16:42 -0400 Received: from shell0.pdx.osdl.net (fw.osdl.org [65.172.181.6]) by smtp.osdl.org (8.12.8/8.12.8) with ESMTP id k9HHGMaX019025 (version=TLSv1/SSLv3 cipher=EDH-RSA-DES-CBC3-SHA bits=168 verify=NO); Tue, 17 Oct 2006 10:16:22 -0700 Received: from localhost (shell0.pdx.osdl.net [10.9.0.31]) by shell0.pdx.osdl.net (8.13.1/8.11.6) with ESMTP id k9HHGL60029221; Tue, 17 Oct 2006 10:16:21 -0700 To: Junio C Hamano In-Reply-To: <7vvemjmlo2.fsf@assigned-by-dhcp.cox.net> X-Spam-Status: No, hits=-0.476 required=5 tests=AWL X-Spam-Checker-Version: SpamAssassin 2.63-osdl_revision__1.95__ X-MIMEDefang-Filter: osdl$Revision: 1.155 $ X-Scanned-By: MIMEDefang 2.36 Sender: git-owner@vger.kernel.org Precedence: bulk X-Mailing-List: git@vger.kernel.org Archived-At: On Tue, 17 Oct 2006, Junio C Hamano wrote: > > * The 'maint' branch has this fix and produced 1.4.2.4 release. > > Linus Torvalds (1): > Fix hash function in xdiff library There's two things to note about this: - the libxdiff dependencies are broken, so it's likely that you need to do a "make clean; make" to actually see the result of this. We really should fix this. I was bitten by this _again_ when I wanted to do some performance testing, and was scratching my head about why it didn't seem to matter. I haven't looked into which part of the Makefile is broken yet, so I really don't know what's broken, but maybe somebody who likes makefiles could take a look? Basically, doing a touch xdiff/xmacros.h should cause a recompile of a lot more than it causes. - while the hash function problem _can_ cause really huge slowdowns in some unlucky situations, it actually causes noticeable performance issues even for normal situations. For example, for me on a 2GHz merom machine in the current git directory: Before: [torvalds@merom git]$ time ./git log -p | wc -l 746211 real 0m27.223s user 0m26.894s sys 0m0.424s After: [torvalds@merom git]$ time ./git log -p | wc -l 746211 real 0m9.638s user 0m9.329s sys 0m0.468s so there's a factor-of-three difference here even on a "normal" load like git itself. You don't need a huge file with tons of changes to see the effect of this. So we should fix the makefile to add whatever proper header file dependencies, but we should also make sure that whoever builds binaries has done a "make clean", otherwise the fix is potentially hidden. Linus