From: Eli Zaretskii <eliz@gnu.org>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: handa@gnu.org, emacs-devel@gnu.org
Subject: Re: Enlarge MAX_ALLOCA?
Date: Fri, 20 Jun 2014 10:08:09 +0300 [thread overview]
Message-ID: <83ionwrrc6.fsf@gnu.org> (raw)
In-Reply-To: <jwv38f0wseb.fsf-monnier+emacs@gnu.org>
> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: Kenichi Handa <handa@gnu.org>, emacs-devel@gnu.org
> Date: Thu, 19 Jun 2014 16:37:07 -0400
>
> >> It makes the potential max increment of stack space "per
> >> lisp-eval-depth" larger, and hence increases the risk that we'll eat up
> >> our stack before we bump into max-lisp-eval-depth.
> > Which functions relevant to max-lisp-eval-depth use SAFE_ALLOCA?
>
> I don't know. Maybe none, but that would surprise me.
I will take a look.
Alternatively, how about using a different limit just in the 2 users
of ALLOC_CONVERSION_WORK_AREA?
> >> I think it makes a lot of sense to try and allocate this space on the
> >> stack when decoding file names, but why does it allocate such a huge
> >> buffer just to en/decode a puny file name?
> > That buffer is fixed in size, I don't know why. Perhaps it's hard to
> > know in advance how much we will need.
>
> Supposedly, every coding system comes with a "blow up factor" (can't
> remember the name we use) which should be usable to compute a safe
> upper-bound.
I don't think the work area is what you think it is. It is not for
the result of the encoding/decoding; that is allocated elsewhere, and
indeed uses a dynamic size computed from the source size. This work
area is for something else: for handling composition annotations
(whatever that is). See handle_composition_annotation and
produce_annotation in coding.c.
> > Again, the problem is memory fragmentation and the resulting large
> > footprint, not the cost of the allocation.
>
> Is this memory fragmentation problem hypothetical, or have we seen
> evidence of it?
Hypothetical. I just don't like seeing such frequent sequences of
malloc(64K)/free() one after the other several times a second in a
live session.
next prev parent reply other threads:[~2014-06-20 7:08 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-19 16:02 Enlarge MAX_ALLOCA? Eli Zaretskii
2014-06-19 16:23 ` David Kastrup
2014-06-19 16:48 ` Eli Zaretskii
2014-06-19 17:04 ` David Kastrup
2014-06-19 17:14 ` Eli Zaretskii
2014-06-19 17:36 ` David Kastrup
2014-06-19 17:51 ` Eli Zaretskii
2014-06-19 18:21 ` Stefan Monnier
2014-06-19 21:13 ` David Kastrup
2014-06-20 7:10 ` Eli Zaretskii
2014-06-20 8:08 ` David Kastrup
2014-06-20 8:38 ` Dmitry Antipov
2014-06-20 8:56 ` Eli Zaretskii
2014-06-20 9:26 ` Andreas Schwab
2014-06-20 9:38 ` David Kastrup
2014-06-19 18:28 ` Stefan Monnier
2014-06-19 18:38 ` Eli Zaretskii
2014-06-19 20:37 ` Stefan Monnier
2014-06-20 7:08 ` Eli Zaretskii [this message]
2014-06-20 13:02 ` Stefan Monnier
2014-06-20 13:18 ` Eli Zaretskii
2014-06-20 14:43 ` Stefan Monnier
2014-06-20 14:50 ` Eli Zaretskii
2014-06-20 15:15 ` Herring, Davis
2014-06-20 15:44 ` Dmitry Antipov
2014-06-20 18:36 ` Eli Zaretskii
2014-06-21 13:01 ` K. Handa
2014-06-21 13:59 ` Eli Zaretskii
2014-06-21 17:08 ` Stefan Monnier
2014-06-22 9:22 ` K. Handa
2014-06-28 14:15 ` K. Handa
2014-06-28 14:38 ` Eli Zaretskii
2014-06-21 15:19 ` David Kastrup
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