Re: Concurrency, again

[Daniel Colascione]

On 10/27/2016 10:27 AM, Eli Zaretskii wrote:
> > From: Philipp Stephani <address@hidden>
> > Date: Tue, 25 Oct 2016 23:28:51 +0000
> >
> > I've pushed the experimental branch to 'concurrency-libtask'. It's essentially 
> > a simple wrapper around libtask,
> > which implements CSP based on setcontext. I've also implemented a Windows 
> > equivalent based on
> > Windows native fibers, but haven't tried that yet.
>
> Thanks.
>
> Could you perhaps summarize the relative advantages and disadvantages
> of the two concurrency branches?  Your branch doesn't have any
> documentation besides doc strings of the new primitives, so it's not
> easy to grasp the high-level picture by looking at the details.
>
> One issue that bothers me is whether it's wise to use libtask here,
> because the changes you did there seem to imply that we will have to
> maintain the library (which is pretty low-level stuff) as part of
> Emacs.  Isn't using system threads better?

Agreed on system threads vs libtask. Fibers of the sort libtask provides 
(similar to GNU Pth) have some claimed advantages in efficiency in large 
programs with lots of concurrent tasks, but for us, I vote for 
Python-style use of OS threads with a Python-style GIL that we can 
release to do long-running computations and recover from parallelism. (I 
believe the existing concurrency branch runs under this model already, 
but I'll have to take a closer look.) System threads also have much 
better integration with the debugger and other development tools; fibers 
have no offsetting advantages for us.