Re: macOS metal rendering engine in mac port

[Aaron Jensen <aaronjensen@gmail.com>]

On Mon, May 24, 2021 at 1:48 AM Eli Zaretskii <eliz@gnu.org> wrote:
>
> On May 24, 2021 11:07:42 AM GMT+03:00, Aaron Jensen <aaronjensen@gmail.com> wrote:
> > On Mon, May 24, 2021 at 12:37 AM Eli Zaretskii <eliz@gnu.org> wrote:
> > >
> > > Why does it look suspect to you?  Don't you also see the same code
> > called to process the other faces in the buffer?
> >
> > What looks suspect is that the exact same call is made so many times
> > for the exact same faces and that call gets slower proportional to the
> > number of faces you have because of the linear search. Fewer faces ==
> > less work, and when something is called so many times it may be worth
> > further optimization or caching.
>
> But we do the same for every face in the buffer, not just for the line-number face.  When you turn on the line-numbers display, a single face gets added to the faces used by buffer text -- the font-lock faces each major mode uses.  So how come adding just one face to the dozen of others has such effect?

It's not the extra face. It appears that enabling line numbers calls
merge_faces for those two faces a significant number of times. See
below.

> You are right that there are better ways than linear search to look up a face's attributes by its symbol, and there is a patch in the works to do just that.  But the puzzle here is elsewhere.  Especially since you report significant slowdown due to line numbers in "emacs -Q" as well.

Awesome!

> IOW, what puzzles me is not the difference between "emacs -Q" and your customizations, what puzzles me is the difference betwen with and without the line numbers, in the same basic configuration.  It cannot be explained by the length of the frame's face alist alone because in both cases that length is almost identical: you add one face to the list of hundreds.

Agreed, I was only pointing out the length compounding things because
I made the likely incorrect assumption that the number of times
merge_faces was called when line numbers are turned on was expected.

> How many times is it called with line numbers turned off, and what is the increase in the number of calls due to line numbers in percents?  Does it come anywhere near the slowdown shown in your benchmarks?

With it turned off, merge_faces was called 40 times.
lface_from_face_name_no_resolve was called 143,308 times.

With it on, merge_faces was called 147,882 times and
lface_from_face_name_no_resolve was called 661,238

merge_faces: 369705% more calls
lface_from_face_name_no_resolve: 461% more calls

I'll respond to your second email separately.