Re: The Emacs master is much slower than the emacs-27 branch.

[Stephen Berman]

On Fri, 4 Dec 2020 09:04:49 +0000 Alan Mackenzie <acm@muc.de> wrote:

> Hello, Steve.
>
> On Thu, Dec 03, 2020 at 23:17:18 +0100, Stephen Berman wrote:
>> On Thu, 3 Dec 2020 18:15:30 +0000 Alan Mackenzie <acm@muc.de> wrote:
>
>> > Hello, Emacs.
>
>> > I've got pretty much up to date copies of both the master and the
>> > emacs-27 branches.
>
>> > When I run my customary benchmark (see below) on master's src/xdisp.c in
>> > master, it's taking around 34s.  On emacs-27, it's taking 22s.
>
>> Hm, this is odd: I just ran your benchmark on src/xdisp.c (starting
>> Emacs with -Q, both configured with CFLAGS='-Og -g3') and got vastly
>> different timings than you did:
>
>> master:   21.785817861557007
>> emacs-27: 61.3885281085968
>
> Maybe the emacs-27 is built without optimisation for debugging.

As noted above, I build both master and emacs-27 with CFLAGS='-Og -g3'.
Given that, is such a difference still expected?  Eli wrote:
"In unoptimized builds I get almost no difference: Emacs 28 is about 4%
slower than Emacs 27", which also contrasts sharply with my timings.

Steve Berman