Re: elisp-benchmarks

[Eli Zaretskii <eliz@gnu.org>]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Date: Thu, 10 Feb 2022 07:50:34 +0100
> Cc: emacs-devel@gnu.org
> 
> > And we see that Matthias's recent improvements to the bytecode
> > interpreter do make a quite significant difference on several of those
> > microbenchmarks ;-), and also on the bytecompiler benchmark (offsetting
> > the extra work needed for the symbol-with-positions)
> 
> Looks like Matthias's work has made a significant positive impact on
> virtually all the tests.  Great work, Matthias!

I'm also pleased with the speedup of bytecode, but I'm worried by the
potentially negative effect of some of those changes on memory
fragmentation: we now prevent the bytecode strings from being moved by
GC (as part of compacting strings), which could prevent Emacs from
being able to return memory to the OS, and in general increase
fragmentation.  It would be good to measure this effect somehow.  We
had in the recent past some reports about people who have the memory
footprint of their Emacs session on the order of 5 to 10 GB, allegedly
due to large blocks of memory being trapped in a way that we cannot
give them back to the OS.  I hope these changes won't make the
situation worse.