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

[Alan Mackenzie <acm@muc.de>]

Hello, Steve.

On Fri, Dec 04, 2020 at 10:32:16 +0100, Stephen Berman wrote:
> On Fri, 4 Dec 2020 09:04:49 +0000 Alan Mackenzie <acm@muc.de> wrote:
> > 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'.

Apologies.  I hadn't read your post properly.

> 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.

I can't understand why you're getting such a slowdown in your emacs-27.
You've presumably got a modern machine, with plenty of cores and plenty
of RAM, so it shouldn't be swapping, or some other process taking up the
processor.

There's something very strange happening.

> Steve Berman

-- 
Alan Mackenzie (Nuremberg, Germany).