From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Paul Eggert Newsgroups: gmane.emacs.devel Subject: Re: VIRT_ADDR_VARIES Date: Tue, 08 Nov 2011 09:34:57 -0800 Organization: UCLA Computer Science Department Message-ID: <4EB96841.7020701@cs.ucla.edu> References: <4EB73983.1060000@cs.ucla.edu> <4EB86864.5080709@cs.ucla.edu> NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Trace: dough.gmane.org 1320773708 14855 80.91.229.12 (8 Nov 2011 17:35:08 GMT) X-Complaints-To: usenet@dough.gmane.org NNTP-Posting-Date: Tue, 8 Nov 2011 17:35:08 +0000 (UTC) Cc: emacs-devel@gnu.org To: Andreas Schwab Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Tue Nov 08 18:35:04 2011 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([140.186.70.17]) by lo.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1RNpZg-0000CO-0C for ged-emacs-devel@m.gmane.org; Tue, 08 Nov 2011 18:35:04 +0100 Original-Received: from localhost ([::1]:59313 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RNpZf-0008Fk-IB for ged-emacs-devel@m.gmane.org; Tue, 08 Nov 2011 12:35:03 -0500 Original-Received: from eggs.gnu.org ([140.186.70.92]:35015) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RNpZd-0008FM-0W for emacs-devel@gnu.org; Tue, 08 Nov 2011 12:35:02 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RNpZb-00027j-O4 for emacs-devel@gnu.org; Tue, 08 Nov 2011 12:35:00 -0500 Original-Received: from smtp.cs.ucla.edu ([131.179.128.62]:45159) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RNpZb-00027e-F0 for emacs-devel@gnu.org; Tue, 08 Nov 2011 12:34:59 -0500 Original-Received: from localhost (localhost.localdomain [127.0.0.1]) by smtp.cs.ucla.edu (Postfix) with ESMTP id 620C4A60001; Tue, 8 Nov 2011 09:34:58 -0800 (PST) X-Virus-Scanned: amavisd-new at smtp.cs.ucla.edu Original-Received: from smtp.cs.ucla.edu ([127.0.0.1]) by localhost (smtp.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id yvD3A1nS9bv5; Tue, 8 Nov 2011 09:34:58 -0800 (PST) Original-Received: from penguin.cs.ucla.edu (Penguin.CS.UCLA.EDU [131.179.64.200]) by smtp.cs.ucla.edu (Postfix) with ESMTPSA id E456639E8008; Tue, 8 Nov 2011 09:34:57 -0800 (PST) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:7.0) Gecko/20110927 Thunderbird/7.0 In-Reply-To: X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6 (newer, 3) X-Received-From: 131.179.128.62 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.devel:145949 Archived-At: On 11/08/11 00:56, Andreas Schwab wrote: > Paul Eggert writes: > >> Compiling without VIRT_ADDR_VARIES speeds up aset by 44% on my host > > I cannot reproduce that. The difference I get is lost in the noise. This appears to be weirdness on my end -- my host gives reproducible results when I use those executables, but when I build them again I get results showing that VIRT_ADDR_VARIES speeds things up, which can't be right. I'll try to get to the bottom of this but for now please ignore my claim about measurable performance difference. >> Sorry, I don't know the context. What's the bug here? > > $ valgrind src/temacs > [...] > Segmentation fault Is that a segmentation fault in valgrind itself, or in temacs? I don't see why running temacs under valgrind would affect VIRT_ADDR_VARIES; surely valgrind doesn't change the pure array's address. But you're right: if setting VIRT_ADDR_VARIES has no measurable performance difference and if it lets people debug better, that's a pretty strong argument for having it always on.