Re: Enabling native compilation by default when libgccjit is present

[Jose A. Ortega Ruiz]

On Sun, Dec 05 2021, Tim Cross wrote:

> Lars Ingebrigtsen <larsi@gnus.org> writes:
>
>> Po Lu <luangruo@yahoo.com> writes:
>>
>>>> Most distributions will probably release Emacs 28.1 with native
>>>> compilation switched on.
>>>
>>> Why is that so?  Most distributions only build their Emacs packages with
>>> the default options.
>>
>> Several distributions have signalled that they want to ship Emacs with
>> native compilation switched on (and at least one said they're going to
>> be doing a full ahead-of-time build, if I remember correctly) --
>> presumably because that'll give their users a faster Emacs.
>
> Does it actually give that much of a performance boost? It has been a
> couple of months since I tried native compilation in Emacs 28, but when
> I did, I noticed next to no performance improvement at all. In fact, all
> I did notice was lots of warnings and significant delays whenever I
> updated packages.

FWIW, i've used native compilation in master builds on and off for a
couple of months, on GNU/Linux (debian sid), and haven't noticed any
speed difference either. Last time was this week.  The warnings are
gone, not sure if it's because i configured some flag back in the day or
because it's now the default, and the compilation delays are not too
bad; but, as i said, i don't notice any difference other than the fact
that the RAM comsumption of emacs is about 80% higher for long sessions
when i use native compilation (i use emacs for virtually everything,
it's my X11 desktop environment, and have a moderate amount of packages
installed (around 50, i think)).

> I've actually never noticed any speed problems with Emacs. Where there
> are delays, it is due to the synchronous nature of what I'm doing rather
> than basic performance.

That's also mostly my experience.  The only times i have to wait a bit
(some seconds) are for eww to render some pages (and that doesn't happen
often), and those waiting times don't seem to change at all when i
enable native compilation.

I'd be curious to know where people are seeing speedups.

Cheers,
jao
-- 
I have lived in this world just long enough to look carefully the
second time into things that I am most certain of the first
time. -Josh Billings, columnist and humorist (21 Apr 1818-1885)