From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Gregory Heytings via "Emacs development discussions." Newsgroups: gmane.emacs.devel Subject: Re: Redisplay slower in Emacs 28 than Emacs 27 Date: Mon, 07 Dec 2020 15:14:14 +0000 Message-ID: References: <877dptiro7.fsf@gnus.org> Reply-To: Gregory Heytings Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII; format=flowed Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="33641"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Alpine 2.22 (NEB 394 2020-01-19) Cc: emacs-devel@gnu.org To: Lars Ingebrigtsen Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Mon Dec 07 16:18:27 2020 Return-path: Envelope-to: ged-emacs-devel@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1kmIHS-0008fH-Rb for ged-emacs-devel@m.gmane-mx.org; Mon, 07 Dec 2020 16:18:26 +0100 Original-Received: from localhost ([::1]:52516 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kmIHR-0001E6-PZ for ged-emacs-devel@m.gmane-mx.org; Mon, 07 Dec 2020 10:18:25 -0500 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:36908) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kmIDZ-0006nk-FV for emacs-devel@gnu.org; Mon, 07 Dec 2020 10:14:25 -0500 Original-Received: from mx.sdf.org ([205.166.94.24]:54801) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kmIDW-0000Ad-LB for emacs-devel@gnu.org; Mon, 07 Dec 2020 10:14:25 -0500 Original-Received: from sdf.org (IDENT:ghe@faeroes.freeshell.org [205.166.94.9]) by mx.sdf.org (8.15.2/8.14.5) with ESMTPS id 0B7FEG1p028742 (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256 bits) verified NO); Mon, 7 Dec 2020 15:14:16 GMT Original-Received: (from ghe@localhost) by sdf.org (8.15.2/8.12.8/Submit) id 0B7FEGMR017446; Mon, 7 Dec 2020 15:14:16 GMT In-Reply-To: <877dptiro7.fsf@gnus.org> Received-SPF: pass client-ip=205.166.94.24; envelope-from=ghe@sdf.org; helo=mx.sdf.org X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.23 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-mx.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.io gmane.emacs.devel:260480 Archived-At: >> Following the "The Emacs master is much slower than the emacs-27 >> branch." thread, I tested Alan's benchmark on the master branch. The >> platform I used is a 64-bit GNU/Linux computer, with GCC 10.2. >> >> It turns out that the 10-15% slowdown of redisplay in Emacs 28, >> compared to Emacs 27, is due to a single character change, namely the >> "!" character removed in commit 165fd028. > > That sounds rather odd, because the code in question is this: > > for (img = c->buckets[i]; img; img = img->next) > if (img->hash == hash > && equal_lists (img->spec, spec) > > And the ! removed was in front of the equal_list (which was reversed > logically). > > In comparison, the code looks like this in Emacs 27: > > for (img = c->buckets[i]; img; img = img->next) > if (img->hash == hash > && !NILP (Fequal (img->spec, spec)) > I was surprised, too. What I do know is that I observed this 10-15% slowdown consistently, on that particular revision, so it cannot be accidental. As you see on the graphs, I tested about hundred different revisions, each of them ten times.