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

[Ihor Radchenko]

Eli Zaretskii <eliz@gnu.org> writes:

>> The fraction of buf_bytepos_to_charpos increases over repeated benchmark
>> runs.
>
> So buf_bytepos_to_charpos is the main suspect now, I guess.  This
> could happen because either (a) buf_bytepos_to_charpos is called more
> times as session uptime progresses,

Just to clarify. The perf records I did are roughly for the duration of
benchmark-run calls. Nothing more.

> or (b) because each call to
> buf_bytepos_to_charpos becomes more and more expensive.  So I think
> the first question is: how many times is buf_bytepos_to_charpos called
> for each search, or, equivalently, is the CPU time per call used up by
> buf_bytepos_to_charpos stays stable or goes up?  I think perf can
> answer these questions if you ask nicely.

I will look how to do it. Maybe perf probe.
I guess, it will be useful to compile Emacs with debug symbols at this
point.

> Is the buffer in question being edited as time advances?  Or is buffer
> text and everything else in the buffer left unchanged?

Not edited between benchmarks. Remember that I did sequence of
benchmark-run calls and the time gradually increases.

-- 
Ihor Radchenko // yantar92,
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