GNU bug report logs - #77961
31.0.50; Rendering HTML email is very slow since commit #eab14d68b2e72b9a6b8b0cc67c9667c2bfbed4f5

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From: Iñigo Serna <inigoserna <at> gmx.com>
To: Gerd Möllmann <gerd.moellmann <at> gmail.com>
Cc: Ihor Radchenko <yantar92 <at> posteo.net>, Eli Zaretskii <eliz <at> gnu.org>, 77961 <at> debbugs.gnu.org
Subject: bug#77961: 31.0.50; Rendering HTML email is very slow since commit #eab14d68b2e72b9a6b8b0cc67c9667c2bfbed4f5
Date: Tue, 22 Apr 2025 09:28:38 +0200

[Message part 1 (text/plain, inline)]

Hi,

On 22 April 2025 at 09:10 +02, Gerd Möllmann 
<gerd.moellmann <at> gmail.com> wrote:

> Maybe comparing a before/after profile could show something.

I attach a profiler report of opening the same HTML email with 
commit
#eab14d68b2e72b9a6b8b0cc67c9667c2bfbed4f5 reverted (ie, no memset, 
no
for-loop either).

I attached an HTML sample file in a past message.
Opening it inside eww produces a similar slowdown on my system, 
maybe a
bit shorter (~3-4 sec).  Without memset or for-loop is almost
instantaneous.


Thanks,
Iñigo Serna

[profiler-ok.txt (text/plain, attachment)]

[Message part 3 (text/plain, inline)]

> Ihor Radchenko <yantar92 <at> posteo.net> writes:
>
>> Gerd Möllmann <gerd.moellmann <at> gmail.com> writes:
>>>>>> I attach a profiler output, and a HTML file which causes a 
>>>>>> similar
>>>>>> slowdown when opening from eww.
>>>
>>> I'm afraid I don't see much in the profile. Only thing is that 
>>> that
>>> redisplay_internal isn't called often. Which makes it even 
>>> weirder that
>>> glyph matrix enlargement should play a role.
>>
>> Looking into reverse call tree (B), I see that
>>
>>         1874  33% + set-window-configuration
>>
>> takes 1/3 of CPU cycles. Looking into its source, it does deal 
>> with
>> glyph matrices. So, it is the suspect, judging from the 
>> submitted
>> profiler report.
>
> Thanks, indeed.
>
> Which I also find weird. Why is that done in the first place? 
> Anyway,
> that not leading to redisplays, how can adding a memset or 
> for-loop
> settign glyph::frame when adjusting matrices produce a 5x 
> slowdown,
> IIUC? I'm absolutely flabbergasted. That all doesn't add up.
>
> Maybe comparing a before/after profile could show something.

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