How to debug high CPU usage -> hang

How to debug high CPU usage -> hang

[Ken Goldman]

I'm editing in ReST mode, Windows 11, emacs 28.1.

Occasionally, I want to jump (search, etc.) and the CPU usage jumps and 
emacs hangs. I suspect a font-lock issue.

I fixed one by bisecting the text, then changing a table type.  Now I 
have another.

Is there a general way to debug?

Re: How to debug high CPU usage -> hang

[Eli Zaretskii]

> From: Ken Goldman <kgoldman@us.ibm.com>
> Date: Tue, 10 Jan 2023 09:58:58 -0500
> 
> I'm editing in ReST mode, Windows 11, emacs 28.1.
> 
> Occasionally, I want to jump (search, etc.) and the CPU usage jumps and 
> emacs hangs. I suspect a font-lock issue.
> 
> I fixed one by bisecting the text, then changing a table type.  Now I 
> have another.
> 
> Is there a general way to debug?

I can suggest profiling and/or attaching a debugger.

Re: How to debug high CPU usage -> hang

[Ken Goldman]

On 1/10/2023 10:21 AM, Eli Zaretskii wrote:
>> From: Ken Goldman <kgoldman@us.ibm.com>
>> Date: Tue, 10 Jan 2023 09:58:58 -0500
>>
>> I'm editing in ReST mode, Windows 11, emacs 28.1.
>>
>> Occasionally, I want to jump (search, etc.) and the CPU usage jumps and
>> emacs hangs. I suspect a font-lock issue.
>>
>> I fixed one by bisecting the text, then changing a table type.  Now I
>> have another.
>>
>> Is there a general way to debug?
> 
> I can suggest profiling and/or attaching a debugger.
> 

Attaching a debugger to the lisp major mode, or building emacs from
source?

Re: How to debug high CPU usage -> hang

[Eli Zaretskii]

> From: Ken Goldman <kgoldman@us.ibm.com>
> Date: Wed, 11 Jan 2023 15:24:53 -0500
> 
> On 1/10/2023 10:21 AM, Eli Zaretskii wrote:
> >> From: Ken Goldman <kgoldman@us.ibm.com>
> >> Date: Tue, 10 Jan 2023 09:58:58 -0500
> >>
> >> I'm editing in ReST mode, Windows 11, emacs 28.1.
> >>
> >> Occasionally, I want to jump (search, etc.) and the CPU usage jumps and
> >> emacs hangs. I suspect a font-lock issue.
> >>
> >> I fixed one by bisecting the text, then changing a table type.  Now I
> >> have another.
> >>
> >> Is there a general way to debug?
> > 
> > I can suggest profiling and/or attaching a debugger.
> > 
> 
> Attaching a debugger to the lisp major mode, or building emacs from
> source?

Attaching a debugger (GDB) to Emacs when its CPU usage jumps.  This
requires Emacs built with debug info, or installing the separate debug
info from your distro.

Re: How to debug high CPU usage -> hang

[Manuel Giraud]

Eli Zaretskii <eliz@gnu.org> writes:

[...]

>> Attaching a debugger to the lisp major mode, or building emacs from
>> source?
>
> Attaching a debugger (GDB) to Emacs when its CPU usage jumps.  This
> requires Emacs built with debug info, or installing the separate debug
> info from your distro.

And if you get the Emacs source tree, you should read etc/DEBUG that
contains most of the informations you need to do this.
-- 
Manuel Giraud