Re: [External] : Passing buffers to function in elisp

[Petteri Hintsanen]

Stefan Monnier via Users list for the GNU Emacs text editor
<help-gnu-emacs@gnu.org> writes:

>> If `emms-info-native--read-and-decode-ogg-page' is called very often
>> (hundreds of times or more), it's probably better to use one single
>> buffer instead of a fresh temp buffer every single time.

I tried this and, for a moment, I _think_ it shaved off something like
20-25% of the memory usage (according to the memory profiler).  That
would be a big win.

Sadly enough, it was just for a moment, because I cannot replicate it
anymore.  It wasn't a particularly controlled setup, so probably I just
messed up something at some point.  Nonetheless, using a persistent
buffer seems to be the right thing to do, and seeing how many
" *foo-bar-baz*" buffers there are, it even looks like a pattern.

Also, if I interpreted profiler's hieroglyphs correctly, it told me that
this setq

  (setq stream (vconcat stream (plist-get page :stream)))

is a pig -- well, of course it is.  I'm accumulating byte vector by
copying its parts.  Similarly bindat consumes a lot of memory.

I think I can replace vectors with strings, which should, according to
the elisp manual, "occupy one-fourth the space of a vector of the same
elements."  And I guess that accumulation would be best done with a
buffer, not with strings or vectors.

But bindat internals are beyond me.

> That's definitely something to consider.  Another is whether the ELisp
> code was byte-compiled (if not, then all bets are off, the interpreter
> itself generates a fair bit of garbage, especially if you use a lot of
> macros).  

No, it was not byte-compiled.  I don't know how many macros there are.
Just by hand-waving I'd say "not that many".  But again what bindat does
is beyond me.

I'll try byte-compiling after the code is in good enough shape to do
controlled experiments.

> Are you using `bindat-type`?

No, not yet.  I have been thinking about it, not only because the
current implementation is riddled with ugly evals and kludges, but I
want to save the kittens ;-D

I also need to discuss with EMMS maintainer whether using Emacs 28+
feature is okay.



Thanks to all for insights, I learned a lot.
Petteri