From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Alan Mackenzie Newsgroups: gmane.emacs.devel Subject: Re: How the long-lines "optimisation" breaks font locking. Date: Fri, 5 Aug 2022 10:56:20 +0000 Message-ID: References: <87y1w5tahv.fsf@gnus.org> <83sfmc2mph.fsf@gnu.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="4612"; mail-complaints-to="usenet@ciao.gmane.io" Cc: larsi@gnus.org, emacs-devel@gnu.org, gregory@heytings.org To: Eli Zaretskii Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Fri Aug 05 13:10:23 2022 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 1oJvDj-00011K-CA for ged-emacs-devel@m.gmane-mx.org; Fri, 05 Aug 2022 13:10:23 +0200 Original-Received: from localhost ([::1]:41372 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oJvDg-0006ZD-Kv for ged-emacs-devel@m.gmane-mx.org; Fri, 05 Aug 2022 07:10:20 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:33400) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oJv0R-0002PL-NP for emacs-devel@gnu.org; Fri, 05 Aug 2022 06:56:39 -0400 Original-Received: from colin.muc.de ([193.149.48.1]:60731 helo=mail.muc.de) by eggs.gnu.org with smtp (Exim 4.90_1) (envelope-from ) id 1oJv0P-0005gb-DE for emacs-devel@gnu.org; Fri, 05 Aug 2022 06:56:39 -0400 Original-Received: (qmail 95381 invoked by uid 3782); 5 Aug 2022 10:56:21 -0000 Original-Received: from acm.muc.de (p4fe1574c.dip0.t-ipconnect.de [79.225.87.76]) (using STARTTLS) by colin.muc.de (tmda-ofmipd) with ESMTP; Fri, 05 Aug 2022 12:56:20 +0200 Original-Received: (qmail 19014 invoked by uid 1000); 5 Aug 2022 10:56:20 -0000 Content-Disposition: inline In-Reply-To: <83sfmc2mph.fsf@gnu.org> X-Submission-Agent: TMDA/1.3.x (Ph3nix) X-Primary-Address: acm@muc.de Received-SPF: pass client-ip=193.149.48.1; envelope-from=acm@muc.de; helo=mail.muc.de 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_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.29 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:293105 Archived-At: Hello, Eli. On Thu, Aug 04, 2022 at 15:54:34 +0300, Eli Zaretskii wrote: > > Date: Thu, 4 Aug 2022 10:44:05 +0000 > > Cc: emacs-devel@gnu.org, Gregory Heytings > > From: Alan Mackenzie [ .... ] > > > .... because if you, instead of a 10K line in that C++ file, inserted > > > a 1M line, then Emacs would previously hang indefinitely, but with the > > > optimisation, it doesn't. > > Well I tried CC Mode with a 1,000,000 character raw string. It was > > indeed a bit sluggish but "hang indefinitely" is an exaggeration. > Try it with a 20MB raw string, then. And, for good measure, in an > unoptimized build. These are the cases we are trying to make > workable. > If all you are saying is that the default value of long-line-threshold > is too low, we can definitely discuss a better value. > > Having loaded the file in C++ Mode (without the spiking of > > narrow-to-region and widen), it took 90 seconds for M-> (first time). > And you consider that reasonable? No, it wasn't reasonable, but neither was it "hang indefinitely". The problem was a single font-lock clause, after whose removal, the M-> took about 1 second (first time) in the file with a 1,000,000 long line. This clause can be put back into CC Mode and optimised, probably by checking for being inside a literal. All the other sluggishness has also vanished with that change. I still get the overflow in the regexp engine stack on inserting text. That, again, is a bug that surely can be fixed. [ .... ] -- Alan Mackenzie (Nuremberg, Germany).