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

[Eli Zaretskii]

> Date: Fri, 27 Nov 2020 09:52:00 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: fweimer@redhat.com, 43389@debbugs.gnu.org, bugs@gnu.support, 
> dj@redhat.com,
>  carlos@redhat.com, michael_heerdegen@web.de
> 
> > Date: Fri, 27 Nov 2020 09:40:53 +0200
> > From: Eli Zaretskii <eliz@gnu.org>
> > Cc: fweimer@redhat.com, 43389@debbugs.gnu.org, bugs@gnu.support, 
> > dj@redhat.com,
> >  michael_heerdegen@web.de, trevor@trevorbentley.com
> > 
> > > lisp_align_malloc (alloc.c:1195)
> > >  Fcons (alloc.c:2694)
> > >   concat (fns.c:730)
> > >    Fcopy_sequence (fns.c:598)
> > >     timer_check (keyboard.c:4395)
> > >      wait_reading_process_output (process.c:5334)
> > >       sit_for (dispnew.c:6056)
> > >        read_char (keyboard.c:2742)
> > >         read_key_sequence (keyboard.c:9551)
> > >          command_loop_1 (keyboard.c:1354)
> > >           internal_condition_case (eval.c:1365)
> > >            command_loop_2 (keyboard.c:1095)
> > >             internal_catch (eval.c:1126)
> > >              command_loop (keyboard.c:1074)
> > >               recursive_edit_1 (keyboard.c:718)
> > >                Frecursive_edit (keyboard.c:790)
> > >                 main (emacs.c:2080)
> > >  
> > > There is a 171MiB's worth of allocations in that path.
> > > 
> > > There are a lot of traces ending in wait_reading_process_output that
> > > are consuming 50MiB.
> > 
> > Thanks.  If they are like the one above, the allocations are due to
> > some timer.  Could be jabber, I'll take a look at it.  Or maybe
> > helm-ff--cache-mode-refresh, whatever that is; need to look at Helm as
> > well.
> 
> Oops, I got this mixed up: the timer list is from Jean, but the massif
> files are from Trevor.

Double oops: the above just shows that each time we process timers, we
copy the list of the timers first.  Not sure what to do about that.
Hmm...  Maybe we should try GC at the end of each timer_check call?

Is it possible to tell how much time did it take to allocate those
171MB via the above chain of calls?  I'm trying to assess the rate of
allocations we request this way.

Each call to lisp_align_malloc above requests a 1008-byte chunk of
memory for a new block of Lisp conses.  Would it benefit us to tune
this value to a larger or smaller size, as far as glibc's malloc is
concerned?