Re: Concurrency via isolated process/thread

[Po Lu]

Ihor Radchenko <yantar92@posteo.net> writes:

> My point is that it will be very difficult to support such systems in
> future if we decide that we want to rely upon safety of concurrent read
> and write.

It's very unlikely that these systems will exist in the future and that
Emacs will want to run on them.  These assumptions are currently being
made by Linux and the JVM, just to name a few multiprocessor programs
that do so.

If, by some miracle, these systems do appear, Emacs can either run on a
single CPU, or we can revisit our decisions at that time.

> I understood that figure and the associated section differently.
> Do you have some kind of reference showing the performance of
> READ_ONCE/WRITE_ONCE?

The figure is titled ``Figure 5.1: Atomic Increment Scalability on
x86''.  The surrounding text and source code listings make the
comparison taking place unambiguous.

> If we need less interlocks, it will certainly make things easier, but I
> do not want to run into hard-to-debug bugs caused by data races.

And you won't, if you run your program on a machine Emacs currently
supports.