From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.devel Subject: Re: Lisp_Marker size on 32bit systems Date: Fri, 07 Sep 2018 08:16:51 -0400 Message-ID: References: <5a2c709e-aa49-b5b6-3fbe-fb8bd33acb23@cs.ucla.edu> <06d01a4b-9d98-df5b-be8a-aeda449acad7@cs.ucla.edu> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: blaine.gmane.org 1536322654 8105 195.159.176.226 (7 Sep 2018 12:17:34 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Fri, 7 Sep 2018 12:17:34 +0000 (UTC) User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) Cc: emacs-devel@gnu.org To: Paul Eggert Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Fri Sep 07 14:17:29 2018 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fyFhW-0001y2-7n for ged-emacs-devel@m.gmane.org; Fri, 07 Sep 2018 14:17:26 +0200 Original-Received: from localhost ([::1]:38391 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fyFjZ-00031O-KY for ged-emacs-devel@m.gmane.org; Fri, 07 Sep 2018 08:19:33 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:47725) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fyFhB-0000ma-O9 for emacs-devel@gnu.org; Fri, 07 Sep 2018 08:17:06 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fyFh8-00077v-Jq for emacs-devel@gnu.org; Fri, 07 Sep 2018 08:17:05 -0400 Original-Received: from chene.dit.umontreal.ca ([132.204.246.20]:57524) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fyFh8-00073e-CZ for emacs-devel@gnu.org; Fri, 07 Sep 2018 08:17:02 -0400 Original-Received: from pastel.home (lechon.iro.umontreal.ca [132.204.27.242]) by chene.dit.umontreal.ca (8.14.7/8.14.1) with ESMTP id w87CGqPF019721; Fri, 7 Sep 2018 08:16:52 -0400 Original-Received: by pastel.home (Postfix, from userid 20848) id E117068404; Fri, 7 Sep 2018 08:16:51 -0400 (EDT) In-Reply-To: <06d01a4b-9d98-df5b-be8a-aeda449acad7@cs.ucla.edu> (Paul Eggert's message of "Fri, 7 Sep 2018 00:15:57 -0700") X-NAI-Spam-Flag: NO X-NAI-Spam-Threshold: 5 X-NAI-Spam-Score: 0 X-NAI-Spam-Rules: 2 Rules triggered EDT_SA_DN_PASS=0, RV6369=0 X-NAI-Spam-Version: 2.3.0.9418 : core <6369> : inlines <6862> : streams <1797755> : uri <2705033> X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 132.204.246.20 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.21 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" Xref: news.gmane.org gmane.emacs.devel:229392 Archived-At: > Although the first attached patch shrinks sizeof (struct Lisp_Maker) from 32 > to 24 bytes on x86 as requested, allocate_pseudovector still *allocates* 32 > bytes for the struct, as it rounds the size up to the next multiple of > alignof (max_align_t), which is 16 on x86. It's not hard to change that to > 8 (please see 2nd attached patch) but this causes a 20% CPU performance hit > (!) to 'make compile-always' on my platform (AMD Phenom II X4 910e circa > 2010, Fedora 28 x86-64, gcc -m32 -march=native), so I didn't install and > can't recommend the 2nd attached patch. Where does this 20% slow down come from? Stefan