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Re: GNU Emacs 24 Performance Issues in 'add-text-properties


From: joseph . koziatek
Subject: Re: GNU Emacs 24 Performance Issues in 'add-text-properties
Date: Thu, 4 Sep 2014 11:12:22 -0700 (PDT)
User-agent: G2/1.0

On Wednesday, September 3, 2014 4:19:23 PM UTC-4, address@hidden wrote:
> Hello All,
> 
> 
> 
> Recently I started using Gnu Emacs 24.3.1 on Redhat 5 which I built with X 
> support. I've noticed that add-text-properties has a performance issue. Below 
> is a simplified function I wrote many years ago to gray out C & C++ comments. 
> I call it from find-file-hooks and other commands where I select a buffer to 
> edit.
> 
>  
> 
> In Gnu Emacs 21.4.1 this routine is blistering fast on a buffer of C++ code 
> 11,000 lines long with lots of comments. Under Gnu Emacs 24.3.1 I experience 
> a long delay.. 
> 
> 
> 
> If I comment out the calls to 'add-text-properties under 24.3.1, it is super 
> fast, so the 'search-forward commands are not the bottleneck.  
> 
> 
> 
> It is the calls to 'add-text-properties causing the long delay.
> 
> 
> 
> The memory usage (virtual memory and physical memory) reported by ps aux 
> --sort=-rss,-rss looks normal for both versions (VirtMemory=150Mb and 
> Rss=30Mb)  
> 
> 
> 
> I'm running on a 16 Cpu box with 32 Gig ram, so I have plenty of horsepower.
> 
> 
> 
> Any help as to what can be causing this code to run so slow under Gnu Emacs 
> 24 is greatly appreciated. 
> 
> 
> 
> Thanks In Advance 
> 
> Joe
> 
> 
> 
> ===================================================================
> 
> 
> 
> (setq comm-start  "/*" ) 
> 
> (setq comm-end    "*/" )
> 
> (setq slash2      "//" )
> 
> 
> 
> (defun mark-comments ()   ;; highlight all C comments...
> 
>   (interactive)
> 
>     
> 
>        (setq savepos (point))
> 
>        (goto-char (point-min))
> 
>   
> 
>        (setq startc (search-forward comm-start nil t))
> 
>        (setq endc   (search-forward comm-end   nil t))
> 
>        (while (and startc endc)
> 
>            (add-text-properties (- startc 2) (- endc 0)  '(face           
> '(:foreground  "gray")))
> 
>            (add-text-properties (- startc 2) (- endc 0)  '(rear-nonsticky t) )
> 
>            (add-text-properties (- startc 2) (- endc 0)  '(front-sticky t) )
> 
> 
> 
>            (setq startc (search-forward comm-start nil t))
> 
>            (setq endc   (search-forward comm-end   nil t))
> 
>        )
> 
>     
> 
>        (goto-char (point-min))
> 
>        (setq startc (search-forward slash2 nil t))
> 
>        (while startc
> 
>           (end-of-line) 
> 
>           (add-text-properties (- startc 2 ) (point)  '(face           
> '(:foreground  "gray")))
> 
>           (add-text-properties (- startc 2 ) (point)  '(rear-nonsticky t) )
> 
>           (add-text-properties (- startc 2 ) (point)  '(front-sticky t) )
> 
> 
> 
>           (setq startc (search-forward slash2 nil t))
> 
>        )
> 
>        (goto-char savepos)
> 
>     t
> 
> )


Hello Stefan, 

Thanks for your response. This does work well with no interference from 
font-lock-mode because I turn and keep font-lock-mode off when I edit C/C++.  
Actually, I wrote the commenting because font-lock-mode is too slow on large 
C/C++ files.  

Also, my real routine handles "modification" status and I use the 
post-command-hook for real-time commenting as I type, all of which is 
blistering fast running under Emacs 21.4.1 . 

Under Emacs 24.3.1 linux "top" shows the %CPU at 100.0 for 5 seconds when I run 
on 11,000 lines. There is no delay under Emacs 21.4.1 (running same code) as it 
is instantaneous.

As an experiment, I built Gnu Emacs 22.3 from source on the same box and it has 
the same slowness (taking 5 full seconds on 11,000 lines). 

I guess I will have to live with this. I wonder if it has something to do with 
the fact that the versions I built from source are slow?  I know Emacs 21.4.1 
came from the Redhat 5 installation procedure.. 

Joe 

  











 by using (buffer-modified-p) and resetting with  (set-buffer-modified-p arg).  




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