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

[Dmitrii Korobeinikov <dim1212k@gmail.com>]

> 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.

> (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.

чт, 9 апр. 2020 г. в 18:33, Eli Zaretskii <eliz@gnu.org>:
>
> > From: Dmitrii Korobeinikov <dim1212k@gmail.com>
> > Date: Thu, 9 Apr 2020 17:59:04 +0600
> >
> > So, as far as I can see, defaulting to a higher threshold with an idle
> > timer could yield better user experience with practically no
> > significant tradeoffs. Is there something I might be missing here?
>
> 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
> (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.
>
> Now, I'm not saying that we cannot or shouldn't increase the default
> GC threshold, but we must keep these two aspects in mind while
> discussing this.