From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Dmitry Gutov Newsgroups: gmane.emacs.bugs Subject: bug#56682: Fix the long lines font locking related slowdowns Date: Fri, 5 Aug 2022 21:02:35 +0300 Message-ID: References: <837d46mjen.fsf@gnu.org> <8a3eaeef01be5bfaa5ef@heytings.org> <05388e8d8812bfa3695d@heytings.org> <83v8rf5894.fsf@gnu.org> <65cb7c73fd4a999cca00@heytings.org> <8c7321f2f3400a5db9be@heytings.org> <8c7321f2f388e5343475@heytings.org> <8c7321f2f36494299e61@heytings.org> <83v8rc2n1h.fsf@gnu.org> <64084296-1953-8ef8-5938-adfb6fb9b43f@yandex.ru> <83r11uzs8n.fsf@gnu.org> <14845631-c2ef-8371-8606-c858092e3192@yandex.ru> <83mtcizov2.fsf@gnu.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="6565"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.9.1 Cc: 56682@debbugs.gnu.org, gregory@heytings.org, monnier@iro.umontreal.ca To: Eli Zaretskii Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Fri Aug 05 20:03:44 2022 Return-path: Envelope-to: geb-bug-gnu-emacs@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 1oK1fj-0001Vg-Pm for geb-bug-gnu-emacs@m.gmane-mx.org; Fri, 05 Aug 2022 20:03:43 +0200 Original-Received: from localhost ([::1]:54414 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oK1fi-0007Qp-0F for geb-bug-gnu-emacs@m.gmane-mx.org; Fri, 05 Aug 2022 14:03:42 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:38842) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oK1fB-0007On-4P for bug-gnu-emacs@gnu.org; Fri, 05 Aug 2022 14:03:09 -0400 Original-Received: from debbugs.gnu.org ([209.51.188.43]:42483) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1oK1f4-0002q7-5A for bug-gnu-emacs@gnu.org; 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Fri, 05 Aug 2022 11:02:37 -0700 (PDT) Content-Language: en-US In-Reply-To: <83mtcizov2.fsf@gnu.org> X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Original-Sender: "bug-gnu-emacs" Xref: news.gmane.io gmane.emacs.bugs:238933 Archived-At: On 05.08.2022 18:33, Eli Zaretskii wrote: >> Date: Fri, 5 Aug 2022 17:41:51 +0300 >> Cc:monnier@iro.umontreal.ca,56682@debbugs.gnu.org,gregory@heytings.org >> From: Dmitry Gutov >> >>>> And to address the idea of "unlocking" the narrowing: I think I have >>>> demonstrated that the remaining slowdown can be caused purely by the >>>> length of the buffer and how long 'parse-partial-sexp' takes to parse >>>> it. >>> No, you haven't demonstrated that. >> Apply the patch for xdisp.c that I have sent previously (it will be at >> the end of this email too) and recompile Emacs. >> >> Now try two different scenarios. 1,2a and 1,2b. >> >> 1. Visit dictionary.json. It will ask you whether to open such big file >> literally, but after you answer 'y', it will display the beginning of >> the file quickly. >> 2a) Evaluate (benchmark 1 '(save-excursion (parse-partial-sexp 1 >> (point-max)))), note the reported delay. >> >> Kill and re-visit the file. >> >> 1. (same as before) >> 2b) Press M->, note the delay you see. >> >> The delays in scenarios 1,2a and 1,2b should be ~the same. They are so >> in my testing. >> >> Or try this scenario: 1,2a,2b. Step 2b should work instantly here. > How is (parse-partial-sexp 1 (point-max)) related to the issue at > hand? Or perhaps I should answer this way: We move to near EOB. fontification-functions are called. jit-lock calls (font-lock-fontify-region point-near-buffer-end (point-max)) which calls font-lock-fontify-syntactically-region which calls both (syntax-propertize (point-max)) and (syntax-ppss point-near-buffer-end) -> and it calls parse-partial-sexp syntax-propertize will also likely call syntax-ppss itself, probably through the major mode's syntax-propertize-function. But if syntax-propertize-function is nil, parse-partial-sexp gets called anyway, over the whole buffer, which makes it the main workload in fontifying near EOB. Now, if syntax-propertize-function is non-nil, parse-partial-sexp will also call it, and it adds its overhead (sometimes a multiple of p-p-s), which also scales linearly with the length of the buffer. So if one can demonstrate that (parse-partial-sexp (point-min) (point-max)) takes about the same time as it takes to fontify the last screen-ful of a buffer, then that says that everything else that jit-lock does to fontify, is negligible, time-wise.