unofficial mirror of emacs-devel@gnu.org 
 help / color / mirror / code / Atom feed
From: Pip Cet via "Emacs development discussions." <emacs-devel@gnu.org>
To: Helmut Eller <eller.helmut@gmail.com>
Cc: "Gerd Möllmann" <gerd.moellmann@gmail.com>,
	"Eli Zaretskii" <eliz@gnu.org>,
	ofv@wanadoo.es, emacs-devel@gnu.org, acorallo@gnu.org
Subject: Re: Some experience with the igc branch
Date: Mon, 23 Dec 2024 23:20:34 +0000	[thread overview]
Message-ID: <87msgmasx7.fsf@protonmail.com> (raw)
In-Reply-To: <87ttau5afi.fsf@gmail.com>

"Helmut Eller" <eller.helmut@gmail.com> writes:

> On Mon, Dec 23 2024, Pip Cet wrote:
> [...]
>>> Also worth mentioning is that trace_hash uses XHASH, which is probably
>>> problematic in combination with a moving GC.
>>
>> Good catch.  s/XHASH/sxhash_eq/ there, I think?  And let's poison XHASH
>> when MPS is in use?
>
> sxhash_eq doesn't fly with headerless objects.

Which objects would that be?

Right now all IGC objects have headers, right?  Did I miss any?

> It should be obsoleted, IMO.

I don't see why.

Is this about cons cells exclusively?  Because 3 words/cons is too
much (possibly 4 words on W64 or 32-bit systems)?

For vectors we can usually derive the length of the vector from the IGC
header (which has plenty of extra bits), which would have the equivalent
effect.  Strings, symbols, floats shouldn't matter.

That leaves conses.  My guess so far was that you wanted to implement a
hack where a headerless cons is a two-word object that would turn into a
tagged pointer to another two-word object with a header as soon as its
hash value is taken.  That requires slowing down either XCAR or XCDR, I
think, and that's sufficient reason for me not to do it, but I guess I
misunderstood your plans.  This would also mean sxhash_eq would allocate
memory, so it couldn't be called from a signal handler without yet
another workaround.

(Note that cons cells used to store long lists are inherently
inefficient: naively storing an n-element list with a header requires
n+1 words, but even headerless cons cells will require 2*n words.  So if
we really decide we need to reduce cons memory usage, I'd look into that
instead.)

Pip




  reply	other threads:[~2024-12-23 23:20 UTC|newest]

Thread overview: 69+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-12-22 15:40 Some experience with the igc branch Óscar Fuentes
2024-12-22 17:18 ` Gerd Möllmann
2024-12-22 17:29 ` Gerd Möllmann
2024-12-22 17:41 ` Pip Cet via Emacs development discussions.
2024-12-22 17:56   ` Gerd Möllmann
2024-12-22 19:11   ` Óscar Fuentes
2024-12-23  0:05     ` Pip Cet via Emacs development discussions.
2024-12-23  1:00       ` Óscar Fuentes
2024-12-23  3:42       ` Gerd Möllmann
2024-12-23  6:27     ` Jean Louis
2024-12-22 20:29   ` Helmut Eller
2024-12-22 20:50   ` Gerd Möllmann
2024-12-22 22:26     ` Pip Cet via Emacs development discussions.
2024-12-23  3:23       ` Gerd Möllmann
     [not found]         ` <m234ieddeu.fsf_-_@gmail.com>
     [not found]           ` <87ttaueqp9.fsf@protonmail.com>
     [not found]             ` <m2frme921u.fsf@gmail.com>
     [not found]               ` <87ldw6ejkv.fsf@protonmail.com>
     [not found]                 ` <m2bjx2h8dh.fsf@gmail.com>
2024-12-23 14:45                   ` Make Signal handling patch platform-dependent? Pip Cet via Emacs development discussions.
2024-12-23 14:54                     ` Gerd Möllmann
2024-12-23 15:11                       ` Eli Zaretskii
2024-12-23 13:35       ` Some experience with the igc branch Eli Zaretskii
2024-12-23 14:03         ` Discussion with MPS people Gerd Möllmann
2024-12-23 14:04           ` Gerd Möllmann
2024-12-23 15:07         ` Some experience with the igc branch Pip Cet via Emacs development discussions.
2024-12-23 15:26           ` Gerd Möllmann
2024-12-23 16:03             ` Pip Cet via Emacs development discussions.
2024-12-23 16:44               ` Eli Zaretskii
2024-12-23 17:16                 ` Pip Cet via Emacs development discussions.
2024-12-23 18:35                   ` Eli Zaretskii
2024-12-23 18:48                     ` Gerd Möllmann
2024-12-23 19:25                       ` Eli Zaretskii
2024-12-23 20:30                     ` Benjamin Riefenstahl
2024-12-23 23:39                       ` Pip Cet via Emacs development discussions.
2024-12-24 12:14                         ` Eli Zaretskii
2024-12-24 13:18                           ` Pip Cet via Emacs development discussions.
2024-12-24 13:42                           ` Benjamin Riefenstahl
2024-12-24  3:37                       ` Eli Zaretskii
2024-12-24  8:48                         ` Benjamin Riefenstahl
2024-12-24 13:52                           ` Eli Zaretskii
2024-12-24 13:54                             ` Benjamin Riefenstahl
2024-12-23 17:44               ` Gerd Möllmann
2024-12-23 19:00                 ` Eli Zaretskii
2024-12-23 19:37                   ` Eli Zaretskii
2024-12-23 20:49                   ` Gerd Möllmann
2024-12-23 21:43                     ` Helmut Eller
2024-12-23 21:49                       ` Pip Cet via Emacs development discussions.
2024-12-23 21:58                         ` Helmut Eller
2024-12-23 23:20                           ` Pip Cet via Emacs development discussions. [this message]
2024-12-24  5:38                             ` Helmut Eller
2024-12-24  6:27                               ` Gerd Möllmann
2024-12-24 10:09                               ` Pip Cet via Emacs development discussions.
2024-12-24  4:05                       ` Gerd Möllmann
2024-12-24  8:50                         ` Gerd Möllmann
2024-12-24  6:03                     ` SIGPROF + SIGCHLD and igc Gerd Möllmann
2024-12-24  8:23                       ` Helmut Eller
2024-12-24  8:39                         ` Gerd Möllmann
2024-12-24 13:05                         ` Eli Zaretskii
2024-12-24 12:54                       ` Eli Zaretskii
2024-12-24 12:59                         ` Gerd Möllmann
2024-12-23 23:37                   ` Some experience with the igc branch Pip Cet via Emacs development discussions.
2024-12-24  4:03                     ` Gerd Möllmann
2024-12-24 10:25                       ` Pip Cet via Emacs development discussions.
2024-12-24 10:50                         ` Gerd Möllmann
2024-12-24 13:15                         ` Eli Zaretskii
2024-12-24 12:26                       ` Eli Zaretskii
2024-12-24 12:56                         ` Gerd Möllmann
2024-12-24 13:19                           ` Pip Cet via Emacs development discussions.
2024-12-24 13:38                             ` Gerd Möllmann
2024-12-24 13:46                           ` Eli Zaretskii
2024-12-24 14:12                             ` Gerd Möllmann
2024-12-24 14:40                               ` Eli Zaretskii
2024-12-24 12:11                     ` Eli Zaretskii

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

  List information: https://www.gnu.org/software/emacs/

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=87msgmasx7.fsf@protonmail.com \
    --to=emacs-devel@gnu.org \
    --cc=acorallo@gnu.org \
    --cc=eliz@gnu.org \
    --cc=eller.helmut@gmail.com \
    --cc=gerd.moellmann@gmail.com \
    --cc=ofv@wanadoo.es \
    --cc=pipcet@protonmail.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
Code repositories for project(s) associated with this public inbox

	https://git.savannah.gnu.org/cgit/emacs.git

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).