Re: Garbage collector: is 800kb a good default?

[Eli Zaretskii <eliz@gnu.org>]

> From: Dmitrii Korobeinikov <dim1212k@gmail.com>
> Date: Thu, 9 Apr 2020 19:44:40 +0600
> Cc: emacs-devel <emacs-devel@gnu.org>
> 
> > Two things: (1) the timer will not run as long as Emacs is running
> > some prolonged calculation, which could produce a lot of garbage; and
> 
> True, that's a reason for not making it too high. Emacs would also
> freeze very noticably in those cases. But I think the threshold
> doesn't have to be very high to reap most of the the benefits. For
> example, I am testing 80MB at the moment. Pretty sure I would be
> satisfied with half that. By satisfied I mean 3.5k lines of scroll
> action would still be plenty (before a ~1/3-1/2 second gc freeze
> happens) and the startup time would be shaved off quite close to the
> apparent limit anyway.

The "right" value depends on your usage patterns, among other
factors.  How to account for that in the default value?

> > (2) you seem to ignore the increased memory pressure on the rest of
> > the system from the growing memory footprint of Emacs.  On GNU/Linux,
> > Emacs doesn't really return malloc'ed memory to the system, so once
> > the memory footprint grows, it more or less stays that way even after
> > GC.
> 
> Didn't know about that. A ground of reasoning here could be what the
> average user would see as acceptable. Of course, there are also people
> who optimize their system for memory consumption. But they are
> probably tech-savvy enough to find the gc options anyway.

The effect also depends on how much VM does the user have on his/her
system, and what other applications routinely run there.  Since we are
talking about defaults, we should find a setting that is safe,
i.e. works for everyone.