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From: Alan Mackenzie <acm@muc.de>
To: Kan-Ru Chen <kanru@kanru.info>
Cc: emacs-devel@gnu.org
Subject: Re: Slow fontification in C mode buffers
Date: Wed, 21 Dec 2011 10:56:26 +0000	[thread overview]
Message-ID: <20111221105626.GA3263@acm.acm> (raw)
In-Reply-To: <87pqfngp3r.fsf@isil.kanru.info>

Hello, Kanru.

On Sun, Dec 18, 2011 at 12:06:00AM +0800, Kan-Ru Chen wrote:

> Please forgive me for using the other files, it is closer to the real
> case. You can get the file from

> https://hg.mozilla.org/mozilla-central/raw-file/tip/dom/base/nsDOMClassInfo.cpp

OK, now I understand.  I feel your pain.  ;-(

> (i) Loaded elp and instrumented the c- package.
> (ii) Loaded nsDOMClassInfo.cpp
> (iii) Done M-x c++-mode
> (iv) Done M-x elp-results (to clear the accumulated times)
> (v) C-s battery until failing to find 
> (vi) M-x elp-results.

> Before:

> c-beginning-of-decl-1                          201         13.065947999  0.0650047164
> c-beginning-of-statement-1                     229         13.061191     0.0570357685
> c-crosses-statement-barrier-p                  35466       11.622212999  0.0003277001
> c-font-lock-declarations                       16          9.4090929999  0.5880683124
> c-find-decl-spots                              16          9.4089879999  0.5880617499

> c-at-macro-vsemi-p                             46569       6.6139159999  0.0001420240
> c-in-literal                                   46569       5.4569670000  0.0001171802
> c-literal-limits                               51666       3.1393819999  6.076...e-05
> c-backward-sws                                 176682      1.6644079999  9.420...e-06
> c-beginning-of-macro                           104078      0.5568430000  5.350...e-06

> c-state-safe-place                             72459       0.3154430000  4.353...e-06
> c-parse-state                                  225         0.1421229999  0.0006316577
> c-parse-state-1                                225         0.1385559999  0.0006158044
> c-font-lock-enclosing-decls                    16          0.1365140000  0.0085321250
> c-append-to-state-cache                        196         0.0641449999  0.0003272704

> After:

> c-beginning-of-decl-1                          137         9.6732900000  0.0706079562
> c-beginning-of-statement-1                     165         9.6693369999  0.0586020424
> c-crosses-statement-barrier-p                  25584       8.5505400000  0.0003342143
> c-font-lock-declarations                       16          6.059768      0.3787355
> c-find-decl-spots                              16          6.059666      0.378729125

> c-at-macro-vsemi-p                             35149       4.7420429999  0.0001349126
> c-in-literal                                   35149       4.0154739999  0.0001142414
> c-literal-limits                               38962       2.5425719999  6.525...e-05
> c-backward-sws                                 128214      1.1421259999  8.907...e-06
> c-beginning-of-macro                           78145       0.3845660000  4.921...e-06

> c-state-safe-place                             54703       0.2419970000  4.423...e-06
> c-parse-state                                  317         0.1464209999  0.0004618958
> c-font-lock-enclosing-decls                    16          0.137945      0.0086215625
> c-parse-state-1                                317         0.1331939999  0.0004201703
> c-font-lock-declarators                        24          0.065522      0.0027300833

It looks like my latest change is saving ~25% of the runtime.  That is
not enough, not nearly enough.  Also, your hardware is _much_ faster than
mine.  ;-)

The problem is quite clear - because of the dearth of
semicolons/right-braces, searching backwards to the beginning of
statements (function "c-beginning-of-statement-1") takes forever during
fontification.  To solve this will involve putting a limit on backward
search and somehow coping with not finding BO-statement.

This is going to be a lot of work, and I'm not going to be able to get it
finished this year.  Sorry.  But I'm sure the bug can be fixed.  

In the meantime, I suggest turning font-lock off for this file.

> -- Kanru

-- 
Alan Mackenzie (Nuremberg, Germany).



  reply	other threads:[~2011-12-21 10:56 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-12-03 13:19 Slow fontification in C mode buffers Eli Zaretskii
2011-12-03 15:03 ` Sujith
2011-12-03 15:14   ` Eli Zaretskii
2011-12-03 15:32     ` Sujith
2011-12-03 15:18 ` Alan Mackenzie
2011-12-03 16:19   ` Eli Zaretskii
2011-12-13 15:31   ` Kan-Ru Chen
2011-12-14 11:19     ` Alan Mackenzie
2011-12-14 11:30     ` Alan Mackenzie
2011-12-14 12:23       ` Alan Mackenzie
2011-12-14 13:14     ` Alan Mackenzie
2011-12-14 15:02       ` Kan-Ru Chen
2011-12-15 13:43     ` Alan Mackenzie
2011-12-15 16:16       ` Kan-Ru Chen
2011-12-15 18:12         ` Alan Mackenzie
2011-12-16  2:32           ` Kan-Ru Chen
2011-12-16 11:26             ` Alan Mackenzie
2011-12-17 16:06               ` Kan-Ru Chen
2011-12-21 10:56                 ` Alan Mackenzie [this message]
2011-12-21 13:33                   ` Geoff Gole
2011-12-21 16:04                     ` Alan Mackenzie
2011-12-21 16:48                       ` Geoff Gole
2011-12-21 18:06                         ` Alan Mackenzie
2011-12-21 18:16                     ` Eli Zaretskii
2011-12-21 18:32                       ` Geoff Gole
2011-12-21 19:35                         ` Eli Zaretskii
2011-12-23  1:56                     ` Kentaro NAKAZAWA
2011-12-23 12:03                       ` Alan Mackenzie
2012-01-06 22:08                       ` Alan Mackenzie
2012-01-07  0:09                         ` Kentaro NAKAZAWA
2012-01-07 13:50                           ` Alan Mackenzie
2012-01-08  1:26                             ` Kentaro NAKAZAWA
2012-01-08 10:05                               ` Alan Mackenzie
2012-01-20 17:26                               ` Alan Mackenzie
2012-02-06 16:14                                 ` Kentaro NAKAZAWA
2011-12-22 16:06                   ` Kan-Ru Chen
2012-01-13 19:12                 ` Alan Mackenzie
2012-01-14  9:12                   ` Kan-Ru Chen
2012-01-15 21:12                 ` Alan Mackenzie
2012-01-22  4:20                   ` Kan-Ru Chen
2011-12-03 21:15 ` Alan Mackenzie
2011-12-04  6:00   ` Eli Zaretskii

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