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From: Eli Zaretskii <eliz@gnu.org>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: emacs-devel@gnu.org
Subject: Re: `aset` on strings, changing the size in bytes
Date: Sun, 09 Sep 2018 08:22:06 +0300	[thread overview]
Message-ID: <83y3cbqm81.fsf@gnu.org> (raw)
In-Reply-To: <jwvva7fmys9.fsf-monnier+gmane.emacs.devel@gnu.org> (message from Stefan Monnier on Sat, 08 Sep 2018 18:09:41 -0400)

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Date: Sat, 08 Sep 2018 18:09:41 -0400
> 
> >> The need for an indirection (a String_Object has to hold a pointer to an
> >> sdata object rather than being able to keep its payload directly in the
> >> Lisp_String object (using FLEXIBLE_ARRAY_MEMBER))
> > Why is that a problem?
> 
> It slows down every string access, and increases the heap size of every
> string (currently they're something like N bytes of payload plus
> 5 words where 2 of those 5 words are due to the extra indirection).
> 
> For a feature that's almost never used, I think it's pretty costly.

It can be (and was) used by memory-allocation infrastructure,
especially with very large strings.  Are we sure we want to lose it
for slowdown that should be hardly perceptible?



  reply	other threads:[~2018-09-09  5:22 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-09-07 19:52 `aset` on strings, changing the size in bytes Stefan Monnier
2018-09-07 21:33 ` Johan Bockgård
2018-09-07 23:12   ` Paul Eggert
2018-09-07 23:41     ` John Wiegley
2018-09-08  5:17       ` Richard Stallman
2018-09-08  6:34       ` Eli Zaretskii
2018-09-08  2:04     ` Stefan Monnier
2018-09-08  2:17       ` Paul Eggert
2018-09-08  6:41     ` Eli Zaretskii
2018-09-08 18:03       ` Stefan Monnier
2018-09-08 18:20         ` Eli Zaretskii
2018-09-08 18:36           ` Stefan Monnier
2018-09-08 20:59             ` Eli Zaretskii
2018-09-08 22:09               ` Stefan Monnier
2018-09-09  5:22                 ` Eli Zaretskii [this message]
2018-09-10  0:18                   ` Stefan Monnier
2018-09-09  6:07           ` Richard Stallman
2018-09-09  6:26             ` Eli Zaretskii
2018-09-09 14:44               ` Noam Postavsky
2018-09-09 15:17                 ` Eli Zaretskii
2018-09-09 16:27                   ` Noam Postavsky
2018-09-10  5:48                     ` Richard Stallman
2018-09-10  3:03                   ` Stefan Monnier
2018-10-16 21:05                   ` Stefan Monnier
2018-09-10  5:47                 ` Richard Stallman
2018-09-10  5:48               ` Richard Stallman
2018-09-10  3:02             ` Stefan Monnier
2018-09-08  6:03 ` Helmut Eller

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