From: Paul Eggert <eggert@cs.ucla.edu>
To: Andy Moreton <andrewjmoreton@gmail.com>
Cc: emacs-devel@gnu.org
Subject: Re: Using __builtin_expect (likely/unlikely macros)
Date: Sat, 20 Apr 2019 08:57:57 -0700 [thread overview]
Message-ID: <9461246c-409b-15fd-943b-3d673c679870@cs.ucla.edu> (raw)
In-Reply-To: <86ef5wd7az.fsf@gmail.com>
Andy Moreton wrote:
> If the patches from this discussion on marking code as cold or
> liely/unlikely does not result in improved code generation and
> measureable performance gains, then they should be dropped as needless
> clutter in the source code.
As I mentioned in <https://lists.gnu.org/r/emacs-devel/2019-04/msg00767.html>
the 'cold' changes that I installed into master improved overall performance on
a largish practical benchmark (cd lisp && make compile-always) by 1.3% on my
platform: Fedora 29, GCC 8.3.1 20190223 (Red Hat 8.3.1-2), AMD Phenom II X4
910e. The other changes proposed in this thread seem to not help performance (or
even hurt it) and we have not installed them.
I like to see significant benefits for performance-related changes where the
effects are not obvious. For improvements where the generated code is
"obviously" faster (fewer and simpler instructions, say), I typically don't
bother with measurements as my own time is limited too.
next prev parent reply other threads:[~2019-04-20 15:57 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-15 0:15 Using __builtin_expect (likely/unlikely macros) Alex Gramiak
2019-04-15 1:18 ` Paul Eggert
2019-04-15 3:11 ` Alex Gramiak
2019-04-15 4:41 ` Paul Eggert
2019-04-16 0:16 ` Alex Gramiak
2019-04-16 2:34 ` Eli Zaretskii
2019-04-16 5:33 ` Alex Gramiak
2019-04-16 15:23 ` Eli Zaretskii
2019-04-16 15:47 ` Alex Gramiak
2019-04-16 3:42 ` Paul Eggert
2019-04-16 13:05 ` Stefan Monnier
2019-04-16 15:22 ` Paul Eggert
2019-04-16 16:10 ` Alex Gramiak
2019-04-16 17:54 ` Paul Eggert
2019-04-16 20:50 ` Alex Gramiak
2019-04-16 21:11 ` Alex Gramiak
2019-04-16 21:27 ` Stefan Monnier
2019-04-16 21:27 ` Konstantin Kharlamov
2019-04-18 8:25 ` Paul Eggert
2019-04-18 8:43 ` Konstantin Kharlamov
2019-04-18 13:47 ` Andy Moreton
2019-04-18 17:27 ` Paul Eggert
2019-04-18 17:56 ` Andy Moreton
2019-04-18 19:32 ` Paul Eggert
2019-04-19 13:45 ` Alex Gramiak
2019-04-19 13:58 ` Konstantin Kharlamov
2019-04-19 14:45 ` Alex Gramiak
2019-04-19 17:33 ` Paul Eggert
2019-04-19 20:53 ` Alex Gramiak
2019-04-20 0:05 ` Alan Mackenzie
2019-04-20 0:42 ` Paul Eggert
2019-04-20 19:46 ` Alan Mackenzie
2019-04-20 15:29 ` Andy Moreton
2019-04-20 15:57 ` Paul Eggert [this message]
2019-04-20 16:03 ` Eli Zaretskii
2019-04-20 16:11 ` Paul Eggert
2019-04-20 16:18 ` Eli Zaretskii
2019-04-20 16:57 ` Paul Eggert
2019-04-20 17:22 ` Eli Zaretskii
2019-04-20 19:13 ` Paul Eggert
2019-04-20 16:28 ` Óscar Fuentes
2019-04-20 18:58 ` Paul Eggert
2019-04-20 19:35 ` Óscar Fuentes
2019-04-20 22:54 ` Paul Eggert
2020-04-15 3:14 ` John Carter
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