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From: Alan Mackenzie <acm@muc.de>
To: Eli Zaretskii <eliz@gnu.org>
Cc: cpitclaudel@gmail.com, charles@aurox.ch,
	michael_heerdegen@web.de, emacs-devel@gnu.org,
	schwab@linux-m68k.org, monnier@IRO.UMontreal.CA
Subject: Re: scratch/accurate-warning-pos: Solid progress: the branch now bootstraps.
Date: Sun, 25 Nov 2018 18:23:30 +0000	[thread overview]
Message-ID: <20181125182330.GG27152@ACM> (raw)
In-Reply-To: <83y39hhvlp.fsf@gnu.org>

Hello, Eli.

On Sun, Nov 25, 2018 at 20:15:30 +0200, Eli Zaretskii wrote:
> > Date: Sun, 25 Nov 2018 17:59:29 +0000
> > From: Alan Mackenzie <acm@muc.de>
> > Cc: cpitclaudel@gmail.com, charles@aurox.ch, michael_heerdegen@web.de,
> > 	emacs-devel@gnu.org, schwab@linux-m68k.org, monnier@IRO.UMontreal.CA

> > > > The idea behind symbols-with-pos-enabled is that it will be a 32/64 bit
> > > > integer permanently in cache, hence can be tested for zero/non-zero
> > > > rapidly.

> > > This is premature optimization, we have gazillions of such tests in
> > > our inner loops (e.g., see bidi.c), one more or one less shouldn't
> > > matter.

> > It's a straightforward way of writing it, without using any contorted
> > code, so even if it is optimisation, it's harmless optimisation.

> The premature optimisation here is to worry about performance without
> timing the code.

> > But right from the beginning of the exercise, I've had speed at the back
> > of my mind.  If the slowdown had been 30%, the Emacs project leadership
> > would have been very unhappy about the idea.

> As I said, I'd be very surprised if using DEFVAR_BOOL would slow down
> what you did in any significant way, beyond the slowdown due to the
> comparison and struct member access.

I'll time it, then we'll know.

> > My current trouble arises from the need to access the variable both from
> > C and from Lisp.

> DEFVAR_BOOL defines a variable accessible both from C and Lisp.

> > I'm still a little confused as to what a DEFVAR_BOOL is.

> It's a C 'bool'.  Look at defvar_bool the function: its last argument
> is a pointer to the C counterpart of a DEFVAR_BOOL.

> You can also use ptype in the debugger to see what it really is, if
> you want to be absolutely sure.

OK, thanks for the explanation.  I'll change the declaration of that
variable (and another one) to DEFVAR_BOOL, and tidy up lisp.h to match.

Then I'll time the resulting Emacs again.  :-)

-- 
Alan Mackenzie (Nuremberg, Germany).



  reply	other threads:[~2018-11-25 18:23 UTC|newest]

Thread overview: 110+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-17 12:45 scratch/accurate-warning-pos: First tentative successes Alan Mackenzie
2018-11-17 13:13 ` Eli Zaretskii
2018-11-23 13:09   ` scratch/accurate-warning-pos: Solid progress: the branch now bootstraps Alan Mackenzie
2018-11-25 11:26     ` Charles A. Roelli
2018-11-25 14:31       ` Alan Mackenzie
2018-11-25 15:12         ` Andreas Schwab
2018-11-25 15:42           ` Alan Mackenzie
2018-11-25 16:40             ` Eli Zaretskii
2018-11-25 17:59               ` Alan Mackenzie
2018-11-25 18:15                 ` Eli Zaretskii
2018-11-25 18:23                   ` Alan Mackenzie [this message]
2018-11-25 19:36                     ` Alan Mackenzie
2018-11-25 16:22         ` Stefan Monnier
2018-11-25 17:35           ` Alan Mackenzie
2018-11-25 18:22             ` Stefan Monnier
2018-11-25 19:54               ` Alan Mackenzie
2018-11-25 20:08                 ` Stefan Monnier
2018-11-26  9:52                   ` Alan Mackenzie
2018-11-26 10:16                     ` Alan Mackenzie
2018-11-25 16:38         ` Eli Zaretskii
2018-11-25 17:27           ` Andreas Schwab
2018-11-25 17:31           ` Alan Mackenzie
2018-11-25 17:39             ` Eli Zaretskii
2018-11-25 18:08               ` Alan Mackenzie
2018-11-25 18:45       ` Paul Eggert
2018-11-25 19:30         ` Alan Mackenzie
2018-11-25 20:12           ` Paul Eggert
2018-11-25 21:29             ` Alan Mackenzie
2018-11-26  1:41               ` Paul Eggert
2018-11-26  3:41                 ` Eli Zaretskii
2018-11-26 17:43                   ` Paul Eggert
2018-11-26 18:43                     ` Alan Mackenzie
2018-11-26 19:18                       ` Clément Pit-Claudel
2018-11-26 19:42                         ` Alan Mackenzie
2018-11-27  1:07                           ` Gemini Lasswell
2018-11-27  1:45                             ` Alan Mackenzie
2018-11-27  6:06                             ` Eli Zaretskii
2018-11-27  2:48                       ` Paul Eggert
2018-11-27  7:43                         ` Alan Mackenzie
2018-11-27 20:27                           ` Paul Eggert
2018-11-27 21:15                             ` Alan Mackenzie
2018-11-27 21:37                               ` Paul Eggert
2018-11-27 21:53                                 ` Alan Mackenzie
2018-11-28  1:11                                   ` Paul Eggert
2018-11-28 12:04                                     ` Alan Mackenzie
2018-11-29 21:28                                       ` Paul Eggert
2018-11-29 22:05                                         ` Alan Mackenzie
2018-11-30 17:50                                           ` Paul Eggert
2018-11-30 18:55                                             ` Alan Mackenzie
2018-11-30 20:14                                               ` Paul Eggert
2018-11-30 22:02                                                 ` Alan Mackenzie
2018-11-30 23:46                                                   ` Paul Eggert
2018-12-01  7:35                                                     ` martin rudalics
2018-12-01  8:25                                                       ` Eli Zaretskii
2018-12-01 11:08                                                         ` Alan Mackenzie
2018-12-01 11:36                                                           ` Eli Zaretskii
2018-12-01 12:47                                                       ` Alan Mackenzie
2018-12-01 14:09                                                         ` martin rudalics
2018-12-01 14:30                                                           ` Stefan Monnier
2018-12-01 16:30                                                             ` martin rudalics
2018-12-01 19:56                                                               ` Stefan Monnier
2018-12-01 14:59                                                           ` Eli Zaretskii
2018-12-01 16:31                                                             ` martin rudalics
2018-12-01 16:53                                                               ` Eli Zaretskii
2018-12-01 19:04                                                                 ` martin rudalics
2018-12-01 19:22                                                                   ` Eli Zaretskii
2018-12-01 17:21                                                           ` Alan Mackenzie
2018-12-01 17:44                                                             ` Michael Heerdegen
2018-12-01 18:58                                                               ` Alan Mackenzie
2018-12-01 20:26                                                                 ` Alan Mackenzie
2018-12-01 17:48                                                             ` Eli Zaretskii
2018-12-01 21:00                                                               ` Paul Eggert
2018-12-01 17:50                                                             ` Clément Pit-Claudel
2018-12-01 18:26                                                               ` Yuri Khan
2018-12-01 19:15                                                                 ` Clément Pit-Claudel
2018-12-01 21:26                                                                 ` Paul Eggert
2018-12-02  6:48                                                                   ` Yuri Khan
2018-12-02 18:39                                                                   ` Gemini Lasswell
2018-12-03  2:28                                                                     ` Stefan Monnier
2018-12-01 19:04                                                             ` martin rudalics
2018-12-02 22:53                                                             ` Dmitry Gutov
2018-12-01  0:26                                               ` Gemini Lasswell
2018-12-01 11:48                                                 ` Alan Mackenzie
2018-11-27 22:09                                 ` Stefan Monnier
2018-11-28  2:18                                   ` Paul Eggert
2018-11-28  2:43                                     ` Stefan Monnier
2018-11-28  5:13                                       ` Paul Eggert
2018-11-28  6:03                                       ` Gemini Lasswell
2018-11-28  5:39                                   ` Gemini Lasswell
2018-11-28 13:06                                     ` Stefan Monnier
2018-11-28  6:28                                 ` Eli Zaretskii
2018-11-28 22:50                                   ` Paul Eggert
2018-11-29  7:19                                     ` Eli Zaretskii
2018-11-29 10:54                                     ` Alan Mackenzie
2018-11-29 11:13                                       ` Eli Zaretskii
2018-11-29 11:37                                         ` Alan Mackenzie
2018-11-29 21:12                                           ` Paul Eggert
2018-11-29 21:28                                             ` Alan Mackenzie
2018-11-28  0:53                               ` Gemini Lasswell
2018-11-26 20:04                     ` Stefan Monnier
2018-11-27  2:51                       ` Paul Eggert
2018-11-26  9:48                 ` Alan Mackenzie
2018-11-26 18:27                   ` Paul Eggert
2018-11-25 18:48     ` Gemini Lasswell
2018-11-25 20:02       ` Stefan Monnier
2018-11-26 12:39       ` Alan Mackenzie
2018-11-26 16:14         ` Gemini Lasswell
2018-11-26 17:06           ` Alan Mackenzie
2018-11-26 17:24             ` Alan Mackenzie
2018-11-29 12:26     ` scratch/accurate-warning-pos: Some real world timings Alan Mackenzie

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