From: Dmitry Gutov <dgutov@yandex.ru>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: "Stephen J. Turnbull" <stephen@xemacs.org>, emacs-devel@gnu.org
Subject: Re: /srv/bzr/emacs/emacs-24 r111116: eval-after-load fix
Date: Sat, 05 Jan 2013 02:32:49 +0400 [thread overview]
Message-ID: <50E75891.7070004@yandex.ru> (raw)
In-Reply-To: <jwv1ue0hlss.fsf-monnier+emacs@gnu.org>
On 04.01.2013 22:10, Stefan Monnier wrote:
>> The arguments that killed purespace for us were (1) most users
>> (including most of those who argued for keeping purespace :-) are in
>> one-xemacs-process-per-machine workflows, and (2) in theory modern
>> virtual memory management by OSes (we were specifically influenced by
>> Linux and Windows) should produce most of the benefits of purespace
>> anyway, since the dumped code contains only a few writable objects,
>> and those tend to be clumped on a very few pages per file, such that
>> the potentially written pages might be measured in 100s of KB out of
>> the 3-5 MB (at that time) of XEmacs memory.
>> I'm not sure I believe (2), though.
>
> I also doubt 2 is true, unless XEmacs's object layout has been changed
> to move the markbit out of their objects. All live objects's markbits
> get written during a GC (except for purespace, of course), regardless of
> the object being read-only.
>
> But I don't see this sharing as tremendously important: we're talking
> about a purespace of about 2MB, for a process whose code size is larger
> and whose minimal runtime size is also a good bit larger.
> Negligible? I don't know! but not terribly important.
>
> OTOH the GC time at start up is reduced by almost a factor 3 (the Lisp
> heap size of "emacs -Q" is about 1MB, whereas it'd be around 3MB if it
> weren't for the purespace). On the third hand, this Gnus process has
> a Lisp heap size of about 100MB, so the purespace makes virtually no
> difference (we'd need a generational GC, instead).
So, it seems to me the main beneficiary of purespace should be code that
launches short-lived Emacs subprocesses, like John Wiegley's emacs-async
package.
I wonder if we can get some numbers on its performance with and without
purespace.
next prev parent reply other threads:[~2013-01-04 22:32 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <E1TqZR5-0007qr-6Z@vcs.savannah.gnu.org>
2013-01-03 1:27 ` /srv/bzr/emacs/emacs-24 r111116: eval-after-load fix Dmitry Gutov
2013-01-03 1:38 ` Glenn Morris
2013-01-03 3:27 ` Stephen J. Turnbull
2013-01-04 5:34 ` Dmitry Gutov
2013-01-04 10:58 ` Stephen J. Turnbull
2013-01-04 18:10 ` Stefan Monnier
2013-01-04 22:32 ` Dmitry Gutov [this message]
2013-01-05 2:54 ` Stephen J. Turnbull
2013-01-04 5:32 ` Dmitry Gutov
2013-01-04 9:39 ` Andreas Schwab
2013-01-04 10:41 ` joakim
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