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From: Alan Mackenzie <acm@muc.de>
To: Eli Zaretskii <eliz@gnu.org>
Cc: larsi@gnus.org, mattiase@acm.org, gregory@heytings.org,
	monnier@iro.umontreal.ca, emacs-devel@gnu.org
Subject: Re: Time to merge scratch/correct-warning-pos into master, perhaps?
Date: Sat, 19 Feb 2022 16:42:07 +0000	[thread overview]
Message-ID: <YhEd394gooPOnGbB@ACM> (raw)
In-Reply-To: <83v8xryh4d.fsf@gnu.org>

Hello, Eli.

On Sun, Feb 06, 2022 at 20:39:14 +0200, Eli Zaretskii wrote:
> > Date: Sun, 6 Feb 2022 18:09:30 +0000
> > Cc: gregory@heytings.org, monnier@iro.umontreal.ca, mattiase@acm.org,
> >   larsi@gnus.org, emacs-devel@gnu.org
> > From: Alan Mackenzie <acm@muc.de>

> > > > > Where are the numbers that show how much slower is the current EQ, for
> > > > > the case of EQ and not-EQ objects?

> > > > We don't have any such numbers.  Is it even possible to measure this?  On
> > > > earlier processors, we could have just counted up processor cycles used
> > > > for each instruction, but not any more.

> > > Yes, it's possible: use perf.

> > I've installed the user side part of perf on my machine.  On reading the
> > tutorial (which is very difficult), it seems perf acts like a super
> > accurate benchmarking program, which measures program runs.

> > Maybe I misunderstand what you meant - but I can't see how perf is able
> > to report the cycles, etc., taken by a single execution of an instance of
> > EQ.

> > What exactly do we want to measure, here?

> Perf is capable of showing profiles at a source line granularity.
> Since the relation of parts of EQ to equal and non-equal objects is
> quite clear, the profile produced by perf can be easily interpreted as
> pertaining to either of these two possibilities.  By comparing the
> profiles with the old and the new definitions of EQ you should be able
> to measure the slowdown we are interested in.

After building each version with CFLAGS='-O2 -g3' and
--with-native-compilation, I've run

    $ perf record -e cpu-clock make check

followed by

    $ perf report -i perf.data --tui

on both old and new EQ versions of Emacs.

On the old version, there is no sign of EQ.  I searched with `/' at the
top level of perf report, and found only other functions with "EQ" in the
name in two non-Emacs libraries.

On the new version, EQ appears just twice when I type `/' EQ RET.  The
total CPU usage appears to be around 0.01%.  In fact the screen looks
like this:

Samples: 576K of event 'cpu-clock:u', Event count (approx.): 144023250000
Overhead  Comma  Shared Object        Symbol
   0.01%  emacs  emacs                [.] EQ
   0.00%  hg     libpython3.9.so.1.0  [.] _PyUnicode_EQ
   0.00%  emacs  emacs                [.] EQ

Typing RET on one of the two EQ lines, then RET again, displays
percentages taken by the various instructions in that particular
expansion of EQ.

I think part of the problem is that EQ isn't in any particular place in
Emacs.  In the C source it occurs over 2,700 times.  Is there any way to
get perf to amalgamate the different occurrences of EQ?

I haven't got any useful information out of the exercise, so far.  I
can't help feeling that I'm missing something.  Is there anything I ought
to be doing that I've not yet done?

> Btw, unlike what you said up-thread, I don't recommend comparing the
> version of Emacs before the merge of the branch with today's
> codebase.  Instead, I suggest to compile two versions of the same
> Emacs codebase, one with the old and simple definition of EQ, the
> other with the definition we use now on master.  This should make the
> comparison easier, since the only difference will be how EQ is
> defined.

-- 
Alan Mackenzie (Nuremberg, Germany).



  reply	other threads:[~2022-02-19 16:42 UTC|newest]

Thread overview: 150+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-15 18:15 Time to merge scratch/correct-warning-pos into master, perhaps? Alan Mackenzie
2022-01-15 18:24 ` Eli Zaretskii
2022-01-16  8:24   ` Lars Ingebrigtsen
2022-01-16  9:51     ` Po Lu
2022-01-16 13:50       ` Alan Mackenzie
2022-01-16 12:02     ` Lars Ingebrigtsen
2022-01-16 12:06       ` Po Lu
2022-01-16 13:12         ` Lars Ingebrigtsen
2022-01-16 14:02           ` Alan Mackenzie
2022-01-17  0:28           ` Po Lu
2022-01-17  3:28             ` Eli Zaretskii
2022-01-17  3:37               ` Po Lu
2022-01-16 14:00         ` Alan Mackenzie
2022-01-16 12:23       ` Eli Zaretskii
2022-01-16 12:26         ` Lars Ingebrigtsen
2022-01-16 12:36           ` Eli Zaretskii
2022-01-16 14:06         ` Alan Mackenzie
2022-01-16 14:11           ` Lars Ingebrigtsen
2022-01-16 14:21           ` Eli Zaretskii
2022-01-16 14:45             ` Alan Mackenzie
2022-01-16 15:04               ` Eli Zaretskii
2022-01-16 15:26                 ` Alan Mackenzie
2022-01-16 15:43                   ` Eli Zaretskii
2022-01-16 15:50                     ` Alan Mackenzie
2022-01-16 13:47     ` Alan Mackenzie
2022-01-16 14:10       ` Lars Ingebrigtsen
2022-01-16 14:59         ` Stefan Monnier
2022-01-16 14:57     ` Stefan Monnier
2022-01-16 15:04       ` Lars Ingebrigtsen
2022-01-16 15:37         ` Alan Mackenzie
2022-01-16 15:50         ` Mattias Engdegård
2022-01-16 16:18           ` Alan Mackenzie
2022-01-16 16:52             ` Mattias Engdegård
2022-01-16 17:13               ` Stefan Monnier
2022-01-16 17:24                 ` Mattias Engdegård
2022-01-22 12:23         ` Alan Mackenzie
2022-01-22 14:30           ` Lars Ingebrigtsen
2022-01-22 15:09             ` Alan Mackenzie
2022-01-22 15:26               ` Lars Ingebrigtsen
2022-01-22 15:36                 ` Eli Zaretskii
2022-01-22 18:30                   ` Alan Mackenzie
2022-01-23 12:45                     ` Lars Ingebrigtsen
2022-01-22 16:06             ` Mattias Engdegård
2022-01-22 17:02               ` Gregory Heytings
2022-01-22 17:46                 ` Eli Zaretskii
2022-01-22 18:01                   ` Gregory Heytings
2022-01-22 18:12                     ` Eli Zaretskii
2022-01-22 22:36                       ` Gregory Heytings
2022-01-22 22:55                         ` Alan Mackenzie
2022-01-23  6:16                         ` Eli Zaretskii
2022-01-23 21:53                           ` Gregory Heytings
2022-01-24  3:37                             ` Eli Zaretskii
2022-01-24 15:20                               ` Gregory Heytings
2022-01-24 16:47                                 ` Eli Zaretskii
2022-01-24 20:41                                   ` Gregory Heytings
2022-01-25  3:34                                     ` Eli Zaretskii
2022-01-25  8:59                                       ` Gregory Heytings
2022-01-25 11:27                                         ` Alan Mackenzie
2022-01-25 13:27                                           ` Stefan Monnier
2022-01-25 18:27                                             ` Alan Mackenzie
2022-01-25 19:26                                               ` Stefan Monnier
2022-01-25 20:58                                                 ` Alan Mackenzie
2022-01-25 21:27                                                   ` Gregory Heytings
2022-01-26 17:32                                                     ` Alan Mackenzie
2022-01-26 18:59                                                       ` Gregory Heytings
2022-01-26 20:26                                                         ` Alan Mackenzie
2022-01-25 22:11                                                   ` Stefan Monnier
2022-01-25 22:42                                                     ` Óscar Fuentes
2022-01-26  1:08                                                       ` Po Lu
2022-01-26 16:56                                                         ` chad
2022-01-26 17:38                                                           ` Eli Zaretskii
2022-01-26 17:58                                                             ` chad
2022-01-26 18:46                                                         ` Gregory Heytings
2022-01-26 19:47                                                           ` Stefan Monnier
2022-01-26 19:59                                                           ` Alan Mackenzie
2022-01-25 21:18                                                 ` Gregory Heytings
2022-01-25 21:38                                             ` Gregory Heytings
2022-01-25 22:21                                               ` Stefan Monnier
2022-01-26 18:36                                                 ` Gregory Heytings
2022-02-04  0:11                                                 ` Gregory Heytings
2022-02-04 11:57                                                   ` Alan Mackenzie
2022-02-04 12:06                                                     ` Eli Zaretskii
2022-02-04 18:31                                                       ` Alan Mackenzie
2022-02-04 18:54                                                         ` Eli Zaretskii
2022-02-04 19:33                                                           ` Alan Mackenzie
2022-02-04 19:46                                                             ` Eli Zaretskii
2022-02-04 21:24                                                               ` Alan Mackenzie
2022-02-04 22:24                                                                 ` Stefan Monnier
2022-02-04 22:30                                                                   ` Stefan Monnier
2022-02-05  7:28                                                                     ` Eli Zaretskii
2022-02-05 18:04                                                                       ` Stefan Monnier
2022-02-05 18:31                                                                         ` Eli Zaretskii
2022-02-05  8:17                                                                 ` Eli Zaretskii
2022-02-06 11:50                                                                   ` Alan Mackenzie
2022-02-06 11:56                                                                     ` Eli Zaretskii
2022-02-06 18:09                                                                       ` Alan Mackenzie
2022-02-06 18:39                                                                         ` Eli Zaretskii
2022-02-19 16:42                                                                           ` Alan Mackenzie [this message]
2022-02-19 17:02                                                                             ` Eli Zaretskii
2022-02-19 17:43                                                                               ` David Engster
2022-02-19 22:10                                                                                 ` Alan Mackenzie
2022-02-20  5:35                                                                                   ` David Engster
2022-02-20 19:45                                                                                     ` Alan Mackenzie
2022-02-20 20:37                                                                                   ` Stefan Monnier
2022-02-20 20:56                                                                                     ` Alan Mackenzie
2022-02-20 23:02                                                                                       ` Stefan Monnier
2022-02-21  0:22                                                                                         ` Óscar Fuentes
2022-02-21  3:31                                                                                           ` Eli Zaretskii
2022-02-21  4:04                                                                                             ` Óscar Fuentes
2022-02-21 12:15                                                                                               ` Eli Zaretskii
2022-02-21 14:55                                                                                                 ` Óscar Fuentes
2022-02-21  3:29                                                                                         ` Eli Zaretskii
2022-02-19 19:01                                                                               ` Stefan Monnier
2022-02-19 19:30                                                                                 ` Eli Zaretskii
2022-02-19 22:03                                                                               ` Alan Mackenzie
2022-02-25 22:29                                                                               ` Alan Mackenzie
2022-02-06 18:40                                                                         ` Eli Zaretskii
2022-02-06 19:03                                                                           ` Eli Zaretskii
2022-02-07 17:36                                                                             ` Andrea Corallo
2022-02-05  6:08                                                   ` Lars Ingebrigtsen
2022-02-05 11:42                                                     ` Alan Mackenzie
2022-02-05 21:31                                                       ` Lars Ingebrigtsen
2022-02-06  7:02                                                         ` Eli Zaretskii
2022-02-06 11:38                                                         ` Alan Mackenzie
2022-02-06 23:14                                                           ` Lars Ingebrigtsen
2022-01-25 21:15                                           ` Gregory Heytings
2022-01-25 21:30                                             ` Andrea Corallo
2022-01-26 18:43                                               ` Gregory Heytings
2022-01-26 21:04                                                 ` Andrea Corallo
     [not found]                                           ` <b0265c41-7ead-4913-667-d0e76a35b3ba@heytings.org>
2022-01-25 21:16                                             ` Gregory Heytings
2022-01-25 12:26                                         ` Eli Zaretskii
2022-01-26 18:41                                           ` Gregory Heytings
2022-01-26 18:59                                             ` Eli Zaretskii
2022-01-26 19:14                                               ` Stefan Monnier
2022-01-26 19:32                                                 ` Eli Zaretskii
2022-01-26 19:34                                             ` Alan Mackenzie
2022-01-22 18:35                 ` Alan Mackenzie
2022-01-22 18:45                   ` Gregory Heytings
2022-01-22 18:50                     ` Eli Zaretskii
2022-01-22 20:07                       ` Gregory Heytings
2022-01-23  5:32                         ` Eli Zaretskii
2022-01-23 21:44                           ` Gregory Heytings
2022-01-15 22:57 ` Stefan Monnier
2022-01-16  0:27 ` Brahimi Saifullah
2022-01-16 14:53   ` Alan Mackenzie
2022-01-16 16:45     ` Brahimi Saifullah
2022-01-22 11:41       ` Alan Mackenzie
2022-01-22 23:16         ` Brahimi Saifullah
2022-01-23 14:09           ` Alan Mackenzie
2022-01-17  9:38 ` Andrea Corallo

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