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: [PATCH] Re: cc-mode fontification feels random Date: Tue, 31 Aug 2021 16:46:15 +0000 Message-ID: References: <835yvmka50.fsf@gnu.org> <9377d9ec-a3e5-ceea-8a9a-523a420f13f7@dancol.org> <83v93lsq83.fsf@gnu.org> <83eea9shyj.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="30652"; mail-complaints-to="usenet@ciao.gmane.io" Cc: dancol@dancol.org, monnier@iro.umontreal.ca, emacs-devel@gnu.org To: Eli Zaretskii Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Tue Aug 31 19:19:40 2021 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 1mL7QC-0007iY-M0 for ged-emacs-devel@m.gmane-mx.org; Tue, 31 Aug 2021 19:19:40 +0200 Original-Received: from localhost ([::1]:51328 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mL7QB-0003tw-KJ for ged-emacs-devel@m.gmane-mx.org; Tue, 31 Aug 2021 13:19:39 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:47336) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mL6tx-0001Ms-7F for emacs-devel@gnu.org; Tue, 31 Aug 2021 12:46:21 -0400 Original-Received: from colin.muc.de ([193.149.48.1]:39776 helo=mail.muc.de) by eggs.gnu.org with smtp (Exim 4.90_1) (envelope-from ) id 1mL6tu-0001k8-44 for emacs-devel@gnu.org; Tue, 31 Aug 2021 12:46:21 -0400 Original-Received: (qmail 89294 invoked by uid 3782); 31 Aug 2021 16:46:15 -0000 Original-Received: from acm.muc.de (p4fe158c5.dip0.t-ipconnect.de [79.225.88.197]) (using STARTTLS) by colin.muc.de (tmda-ofmipd) with ESMTP; Tue, 31 Aug 2021 18:46:15 +0200 Original-Received: (qmail 6677 invoked by uid 1000); 31 Aug 2021 16:46:15 -0000 Content-Disposition: inline In-Reply-To: <83eea9shyj.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 autolearn=unavailable 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:273615 Archived-At: Hello, Eli. On Tue, Aug 31, 2021 at 19:21:40 +0300, Eli Zaretskii wrote: > > Date: Tue, 31 Aug 2021 16:02:45 +0000 > > Cc: monnier@iro.umontreal.ca, dancol@dancol.org, emacs-devel@gnu.org > > From: Alan Mackenzie > > > What happens if you unleash this jit-lock-single-fontification, and > > > then type at a relatively slow pace: does Emacs still feel responsive > > > enough? And how much of CPU does it use in that case? > > I'm guessing at the moment > Well, my point, if it wasn't clear, was to suggest that you or someone > else actually try that and see what happens and how does it feel. > Emacs is a complex beast, so the results might surprise us all. Yes, you were clear, sorry I was not as clear in my reply. I'm currently working out how to implement it. It shouldn't be too difficult or take too long. > > but I'm reckoning that if jit-lock-single-fontification uses > > (marginally over) 0.05s at a time, followed by (at least) 0.1s > > break, normal typing at up to ten characters per second shouldn't be > > affected. > Not sure where did the 0.05 sec number come from. I remember reading somewhere that this is the approximate length of time which is effectively instantaneous to the human consciousness. It would in any case be a configurable option. > You want to limit the fontification of a chunk to that time, but we > don't have an efficient method of doing that, because Emacs is not an > interrupt-driven program. On my 4 year old HW, approximately 5 CC Mode chunks fit into that time, on average. I think the way to do it is to fontify a chunk at a time, and if the 0.05s hasn't yet been used up, fontify another one, and so on. This should work fine on a modern machine, it might cause sluggishness on an older slower machine, which would be fontifying a single chunk which might take, say, 0.1s or 0.2s. This might necessitate different settings than for a fast machine. > So if a Lisp program starts some heavy processing, it will only be > able to stop when it gets to looking at how much time passed, or tests > some flag set by a signal handler. There can be no guarantee this can > never exceed 50 msec. No. But doing a chunk at a time, checking the clock after each chunk, will probably be granular enough. Again, lets try it and see. > > As for how much CPU, then I think it would use one third of a single > > core's CPU time on an otherwise idle Emacs. That's 0.05s strenuous > > activity followed by 0.1s break. > 30% of an execution unit is not negligible. When I see something like > that on my system that I presume should be idle, I start looking for > an offender. And I'm not sure the 30% estimate is accurate. Once > again, let's measure it. Indeed! -- Alan Mackenzie (Nuremberg, Germany).