From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.devel Subject: Re: `aset` on strings, changing the size in bytes Date: Sun, 09 Sep 2018 08:22:06 +0300 Message-ID: <83y3cbqm81.fsf@gnu.org> References: <88must56x4.fsf@gnu.org> <83efe4trsa.fsf@gnu.org> <83lg8bsvfm.fsf@gnu.org> <83k1nvso1o.fsf@gnu.org> NNTP-Posting-Host: blaine.gmane.org X-Trace: blaine.gmane.org 1536470438 16495 195.159.176.226 (9 Sep 2018 05:20:38 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 9 Sep 2018 05:20:38 +0000 (UTC) Cc: emacs-devel@gnu.org To: Stefan Monnier Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Sun Sep 09 07:20:33 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 1fys9B-0004CT-1f for ged-emacs-devel@m.gmane.org; Sun, 09 Sep 2018 07:20:33 +0200 Original-Received: from localhost ([::1]:46108 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fysBH-0000f4-Cr for ged-emacs-devel@m.gmane.org; Sun, 09 Sep 2018 01:22:43 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:50332) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fysAf-0000et-VF for emacs-devel@gnu.org; Sun, 09 Sep 2018 01:22:06 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fysAb-0004Ga-TM for emacs-devel@gnu.org; Sun, 09 Sep 2018 01:22:05 -0400 Original-Received: from fencepost.gnu.org ([2001:4830:134:3::e]:32892) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fysAb-0004GL-P6; Sun, 09 Sep 2018 01:22:01 -0400 Original-Received: from [176.228.60.248] (port=4463 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from ) id 1fysAb-0000Qd-CR; Sun, 09 Sep 2018 01:22:01 -0400 In-reply-to: (message from Stefan Monnier on Sat, 08 Sep 2018 18:09:41 -0400) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 2001:4830:134:3::e 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:229537 Archived-At: > From: Stefan Monnier > Date: Sat, 08 Sep 2018 18:09:41 -0400 > > >> The need for an indirection (a String_Object has to hold a pointer to an > >> sdata object rather than being able to keep its payload directly in the > >> Lisp_String object (using FLEXIBLE_ARRAY_MEMBER)) > > Why is that a problem? > > It slows down every string access, and increases the heap size of every > string (currently they're something like N bytes of payload plus > 5 words where 2 of those 5 words are due to the extra indirection). > > For a feature that's almost never used, I think it's pretty costly. It can be (and was) used by memory-allocation infrastructure, especially with very large strings. Are we sure we want to lose it for slowdown that should be hardly perceptible?