bug#43389: 28.0.50; Emacs memory leaks using hard disk all time

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: trevor@trevorbentley.com,  carlos@redhat.com,  fweimer@redhat.com,
>   43389@debbugs.gnu.org,  bugs@gnu.support,  dj@redhat.com,
>   michael_heerdegen@web.de
> Date: Sat, 12 Dec 2020 14:46:20 -0500
> 
> > Sure.  But isn't that the same as what I said, just from another POV?
> > "A lot of objects to sweep" means there are many objects that aren't
> > live and need to have their memory freed.
> >
> > Since GC wasn't run for many hours, having a lot of garbage to collect
> > is expected, right?
> 
> Could be, but for tens of minutes?

If the system is paging, it could take that long, yes.

> AFAIK gc_sweep shouldn't cause too much thrashing either (the sweep is
> a mostly sequential scan of memory, so even if the total heap is larger
> than your total RAM, it should be ~O(total heap size / bandwidth from
> swap partition)), so I can't imagine how we could spend tens of minutes
> doing gc_sweep (or maybe the time is spend in gc_sweep but doing
> something else than the sweep itself, e.g. handling weak pointers, or
> removing dead markers from marker lists, ... still seems hard to
> imagine spending tens of minutes, tho).

Does gc_sweep involve touching all the memory we free?