Subject: Re: bug#58558: 29.0.50; re-search-forward is slow in some buffers

From: Lars Ingebrigtsen <[email-masked]>
Date: Tue, 18 Oct 2022 20:19:24 +0200

Eli Zaretskii <[email-masked]> writes:

>> I briefly tried to use "perf" under Linux to connect to a running
>> Emacs and get some data out of it, but...  er...  I've never used it
>> before, and...
>> 
>> Does anybody have a recipe for how to do runtime function tracing for a
>> running process?
>
> The way I run perf is to start Emacs under perf to begin with.
>
> What did you try?  It was quite simple, AFAIR, last time I tried.

I thought it might be easier to see the differences in results if one
first attached perf to a fresh (fast) Emacs and got the trace, and the
waited until Emacs got slow, and repeated the same thing under another
trace.

perf is able to do this by:

perf record -p <PID> -g

and

perf report

then shows me stuff, but I don't even know what to look for when
interpreting that.  Or whether perf is, indeed, the right too for this
task.