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bug#21028: Performance regression in revision af1a69f4d17a482c359d98c00e

From: Clément Pit--Claudel
Subject: bug#21028: Performance regression in revision af1a69f4d17a482c359d98c00ef86fac835b5fac (Apr 2014).
Date: Sat, 18 Jul 2015 03:24:02 -0700
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0

On 07/15/2015 05:32 AM, Dmitry Antipov wrote:
> On 07/10/2015 07:55 PM, Clément Pit--Claudel wrote:
>> The figures are very similar to the tests above: with that patch inserting 
>> 50 lines takes 3 seconds,
>> and without it it's instantaneous. Thus I think it's safe to say that this 
>> particular patch is indeed
>> responsible for the performance regression. But maybe I'm missing something?
> As of c40ea1328bb33abaec14f1fc92ac2349b5ee2715, I can't reproduce this issue, 
> with your fontset setup
> from http://debbugs.gnu.org/cgi/bugreport.cgi?bug=21028#17. Cursor motion and 
> keyboard/mouse selection
> are smooth, and CPU/memory usage looks normal.

Thanks for trying this out. Thanks for your suggestions, too.

> My suggestions are:
> 1) Re-run your timed tests from 
> http://debbugs.gnu.org/cgi/bugreport.cgi?bug=21028#20 under /usr/bin/time,
> not time (the latter is a simple shell builtin). /usr/bin/time also shows 
> memory usage; if "bad" (current)
> instance consumes more memory than "good" (with reverted change) one, there 
> may be nasty GC issue.

The timings are similar:

$ /usr/bin/time emacs-bad/src/emacs -Q --eval "(progn (dotimes (_ 3) 
(set-fontset-font t 'unicode (font-spec :name \"Arial\") nil 'append)) (dotimes 
(_ 500) (insert \"日本国\n\")) (dotimes (_ 500) (previous-line) (redisplay t)) 
13.31user 8.57system 0:34.54elapsed 63%CPU (0avgtext+0avgdata 50592maxresident)k
0inputs+0outputs (0major+4958minor)pagefaults 0swaps

$ /usr/bin/time emacs-good/src/emacs -Q --eval "(progn (dotimes (_ 3) 
(set-fontset-font t 'unicode (font-spec :name \"Arial\") nil 'append)) (dotimes 
(_ 500) (insert \"日本国\n\")) (dotimes (_ 500) (previous-line) (redisplay t)) 
0.58user 0.03system 0:01.05elapsed 58%CPU (0avgtext+0avgdata 50392maxresident)k
29840inputs+0outputs (105major+4911minor)pagefaults 0swaps

> 2) 3 seconds is large enough to leave the traces in profiled runs. On 
> GNU/Linux, it may be worth trying
> to run under perf, both "good" and "bad" cases, and comparing reports.

I have attached the reports in the good and bad cases (200c532 and af1a69f 
respectively). I'm not sure what to conclude from them; I can provide the full 
trace data if needed.


Attachment: bad-report
Description: Text document

Attachment: good-report
Description: Text document

Attachment: signature.asc
Description: OpenPGP digital signature

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