Re: Reliable after-change-functions (via: Using incremental parsing in Emacs)

[Alan Mackenzie]

Hello, Dmitry.

On Sat, Apr 04, 2020 at 15:01:23 +0300, Dmitry Gutov wrote:
> On 04.04.2020 14:06, Alan Mackenzie wrote:

> >> Interesting. How do you measure it exactly? Do you kill the buffer
> >> between tries?

> > Using my macro time-it, I did:

> > (time-it (find-file "..../src/xdisp.c") (sit-for 0))

> It might be valuable if you evaluated exactly the same form I did. And 
> made sure that the buffer is not visited in advance. And did that in an 
> 'emacs -Q' session.

Fair point:

    M-: (benchmark 1 '(progn (find-file "src/xdisp.c")))

    "Elapsed time: 1.249904s (0.165570s in 7 GCs)"

, in a build with the CLAGS and gtk toolkit like you said.  That's in
agreement with your timing, given my slightly slower machine.


> > .  I think this was without the file yet being in the OS's file cache.
> > Mind you, I have an nvme SSD.

> I do as well. I have a fast laptop, pretty sure it's faster than what 
> 90% of our users have. My single-threaded performance must be better 
> than yours for sure.

> >> I have a fast Intel CPU that is barely 2 years old (i9-8950HK),
> >> system-configuration-options is "--with-x-toolkit=gtk3 'CFLAGS=-Og
> >> -g3'", the build is from emacs-27 branch, recent revision.

> > That's a debugging build, isn't it?  That probably explains the
> > difference.

> Debugging-ish. It hardly explains the 4.5x difference. So we're probably 
> measuring different things.

I think it does explain the difference.  I repeated my previous timing,
which was 0.18s on an optimised build, and it came out at 1.16s.  That's
a factor of 6 different.  CFLAGS='-Og -g3' is a slow build.

-- 
Alan Mackenzie (Nuremberg, Germany).