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From: Pip Cet <pipcet@gmail.com>
To: Stefan Monnier <monnier@iro.umontreal.ca>, eliz@gnu.org
Cc: emacs-devel@gnu.org
Subject: Re: Opportunistic GC
Date: Mon, 8 Mar 2021 07:20:28 +0000	[thread overview]
Message-ID: <CAOqdjBfRJKN_nHLErVThMm7783rrhaHMBv+OmmiZXoaVKL-voQ@mail.gmail.com> (raw)
In-Reply-To: <jwvtupm733z.fsf-monnier+emacs@gnu.org>

On Mon, Mar 8, 2021 at 3:37 AM Stefan Monnier <monnier@iro.umontreal.ca> wrote:
> I've been running with the code below recently to try and see if
> opportunistic GC can be worth the trouble.

Just a random idea: What if we exploit the fact most people have more
than one CPU core these days, garbage-collect in a separate fork()ed
process, then do only the sweeping in the main process?

Immediate advantage: we'd never mark objects in the "real" Emacs
process, making debugging easier.

My implementation proposal would be to pipe(), fork(), run GC, then
send through the pipe the Lisp_Objects which can be collected by the
original Emacs.

For me, it was a bit difficult to see that this would indeed be safe,
but I'm now pretty convinced it would be: objects that are unreachable
in the child Emacs cannot become reachable in the parent Emacs (they
might show up on the stack, but that's a false positive).

We'd have to be careful not to run two "real" GC processes at the same
time. And, of course, we'd require fork() and pipe(), so I'm not sure
this would work on Windows. Furthermore, if we ever decide to fall
back to doing the real GC in the main process, we must not sweep
objects which were determined to be unreachable by a conflicting
henchman process.

And of course it would mean that we would increase memory usage for
GC, so in low-memory situations, we'd have to fall back to traditional
GC.

Eli, would this qualify as a "small" GC change, and thus be vetoed?

Pip



  reply	other threads:[~2021-03-08  7:20 UTC|newest]

Thread overview: 61+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-08  3:35 Opportunistic GC Stefan Monnier
2021-03-08  7:20 ` Pip Cet [this message]
2021-03-08  8:26   ` martin rudalics
2021-03-08  9:02     ` Pip Cet
2021-03-08  9:51       ` martin rudalics
2021-03-08 10:44         ` Pip Cet
2021-03-08 11:37           ` martin rudalics
2021-03-08 12:27             ` Pip Cet
2021-03-08 18:06               ` martin rudalics
2021-03-08 18:24                 ` Concurrent GC via fork (was: Opportunistic GC) Stefan Monnier
2021-03-09  8:10                   ` Concurrent GC via fork martin rudalics
2021-03-10 20:35                 ` Opportunistic GC Pip Cet
2021-03-08 11:38           ` Stefan Kangas
2021-03-08 12:55             ` Pip Cet
2021-03-08 14:06             ` Andrea Corallo via Emacs development discussions.
2021-03-08 14:49           ` Eli Zaretskii
2021-03-08 15:02             ` Pip Cet
2021-03-08 15:23               ` Eli Zaretskii
2021-03-08 15:39                 ` Pip Cet
2021-03-08 16:27                   ` Eli Zaretskii
2021-03-08 16:35                     ` Pip Cet
2021-03-08 17:06                       ` Eli Zaretskii
2021-03-08 15:46               ` Stefan Monnier
2021-03-08 16:11                 ` Pip Cet
2021-03-08 16:37                   ` Stefan Monnier
2021-03-08 14:01   ` Andrea Corallo via Emacs development discussions.
2021-03-08 15:04     ` Pip Cet
2021-03-08 15:50       ` Stefan Monnier
2021-03-08 15:52       ` Andrea Corallo via Emacs development discussions.
2021-03-08 16:14         ` Philipp Stephani
2021-03-08 16:18           ` Andrea Corallo via Emacs development discussions.
2021-03-08 16:40             ` Philipp Stephani
2021-03-08 16:44         ` Stefan Monnier
2021-03-08 17:13           ` Eli Zaretskii
2021-03-10 20:25             ` Pip Cet
2021-03-10 20:48               ` Eli Zaretskii
2021-03-11  7:55                 ` Pip Cet
2021-03-11  8:37                   ` Eli Zaretskii
2021-03-11  9:03                     ` Pip Cet
2021-03-11  9:34                       ` Eli Zaretskii
2021-03-11 10:11                         ` Pip Cet
2021-03-11 11:35                           ` Eli Zaretskii
2021-03-09  6:22           ` Richard Stallman
2021-03-09  8:11             ` Pip Cet
2021-03-10  5:52               ` Richard Stallman
2021-03-08 14:45   ` Eli Zaretskii
2021-03-08 14:57     ` Pip Cet
2021-03-08 15:16       ` Eli Zaretskii
2021-03-09 13:01       ` Eli Zaretskii
2021-03-10 20:21         ` Pip Cet
2021-03-10 20:41           ` Eli Zaretskii
2021-03-11  8:06             ` Pip Cet
2021-03-11  9:03               ` Eli Zaretskii
2021-03-08 16:03   ` Concurrent GC via `fork` (was: Opportunistic GC) Stefan Monnier
2021-03-08 16:25     ` Pip Cet
2021-03-08 17:37       ` Concurrent GC via `fork` Stefan Monnier
2021-03-08 19:21       ` Lars Ingebrigtsen
2021-03-10 17:18   ` Opportunistic GC Matt Armstrong
2021-03-10 19:38     ` Pip Cet
2022-07-05  1:47   ` Stefan Monnier
2022-07-05 13:49     ` T.V Raman

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