Re: Time to merge scratch/correct-warning-pos into master, perhaps?

[David Engster]

>> Date: Sat, 19 Feb 2022 16:42:07 +0000
>> Cc: gregory@heytings.org, monnier@iro.umontreal.ca, mattiase@acm.org,
>>   larsi@gnus.org, emacs-devel@gnu.org
>> From: Alan Mackenzie <acm@muc.de>
>> 
>> I haven't got any useful information out of the exercise, so far.  I
>> can't help feeling that I'm missing something.  Is there anything I ought
>> to be doing that I've not yet done?
>
> Maybe you should make EQ real function, with an attribute that would
> preclude its inlining.
>
> I have no other ideas.  Maybe someone else does.

Making EQ a non-inlined function would be the first step. But since perf
is a sampling profiler, it is not easy to measure something that's
already very quick - it's simply quite unlikely that perf would hit it,
unless it is called extremely often. The default sampling frequency of
perf is 1kHz, so the first thing you can try is to increase that, so
that it becomes more likely to hit EQ (see the '-F' switch for 'perf
record').

However, it might simply be that a tracing profiler would be the better
choice here, so maybe look into good old gprof or valgrind. Or maybe
even instrument EQ yourself and count cycles between start and end.

-David