From: Dmitry Antipov <dmantipov@yandex.ru>
To: Emacs development discussions <emacs-devel@gnu.org>
Cc: Stefan Monnier <monnier@IRO.UMontreal.CA>
Subject: Re: [Emacs-diffs] trunk r114117: * buffer.c (drop_overlay):
Date: Sat, 07 Sep 2013 08:37:14 +0400 [thread overview]
Message-ID: <522AAD7A.3030502@yandex.ru> (raw)
In-Reply-To: <jwvhae1emmw.fsf-monnier+emacs@gnu.org>
[This is from private e-mail to Stefan due to:
<monnier@IRO.UMontreal.CA>: connect to
pinpin.IRO.UMontreal.CA[132.204.24.52]:25: Connection timed out]
On 09/03/2013 11:25 PM, Stefan Monnier wrote:
> Thinking about optimizing markers.
> How 'bout changing unchain_markers so it is constant time: add a new
> "unchained" bit in the Lisp_Marker struct and set it to true there.
> Then reap those markers that are "unchained but still in the list"
> lazily, either during GC or when we traverse the list for some
> other reason, or when we really have to because the marker is being
> re-chained elsewhere (but not if it's being rechained in the same
> buffer).
This looks good, and I'll try to implement this.
I'm also thinking about offloading GC with explicit marker freeing.
For example, save-excursion creates up to 2 markers each time, and
this is the well-known bottleneck because there may be thousands
calls to save-excursion per just one basic editing command in cc-mode.
But we can't use free_marker instead of unchain_marker
in save_excursion_restore because the marker may be recorded in
buffer undo list, and freeing it creates dangling pointer (I hit
this problem in r109221, and the latter was immediately reverted :-().
So I suppose that we need one more bit for internal temporary
markers that are invisible to Lisp and presumably have short lifetime -
such a markers should not be included in undo lists and so can be
safely freed when they're not needed anymore.
Dmitry
next parent reply other threads:[~2013-09-07 4:37 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <E1VGrmg-0000c9-Jm@vcs.savannah.gnu.org>
[not found] ` <jwvhae1emmw.fsf-monnier+emacs@gnu.org>
2013-09-07 4:37 ` Dmitry Antipov [this message]
2013-09-09 19:41 ` [Emacs-diffs] trunk r114117: * buffer.c (drop_overlay): Stefan Monnier
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