Re: Timings for 'make check' with and without symbols with position

[Alan Mackenzie <acm@muc.de>]

Hello, Eli.

On Sun, Feb 27, 2022 at 14:34:24 +0200, Eli Zaretskii wrote:
> > Date: Sun, 27 Feb 2022 12:15:14 +0000
> > From: Alan Mackenzie <acm@muc.de>
> > Cc: ofv@wanadoo.es, deng@randomsample.de, mattiase@acm.org, emacs-devel@gnu.org,
> >  gregory@heytings.org, larsi@gnus.org

> > Char-tables seem to have something to do with it.  The perf output for
> > mark_char_table increase from 2.98% to 3.79%.  Adding the 12.6% factor
> > onto the 3.79% gives us 4.27%.  That's a factor of ~1.5 increase.

> > I'm still slogging through the detailed output for mark_char_table,
> > which is not easy in the optimised build.  I suspect that somehow,
> > somewhere, symbols with position have got themselves into a char-table,
> > and they take (a lot) longer to process than bare symbols (for which
> > mark_char_table is optimised).  I've not yet managed to find such a
> > char-table though.

> We do have a few char-tables whose slots are symbols or include
> symbols.  unicode-category-table is one, for example;
> composition-function-table is another.

I've instrumented mark_char_table to try and detect symbols with
position, but got no hits.

I similarly instrumented mark_vectorlike, but the only hits I got there
seemed to be when a compilation was in progress.

So elucidation eludes me, so far.  I'll need to look at it in some other
fashion (suggestions welcome).

-- 
Alan Mackenzie (Nuremberg, Germany).