Re: [Chicken-users] Best way to share memory between C and Chicken

[Dan Leslie]

With semaphores and shared memory you can basically emulate the 
behaviour you would expect from native threads. Though I'm not certain 
about how comparable it is in performance, I understand it to be quite 
zippy.

Ie, shm_open will give you a file descriptor, which you can then treat 
as a memory buffer by using mmap, and using semaphores you can safely 
signal across processes whether someone is in a critical section or not.

To me, the drawback is in that creating a shared memory object and 
wrapping it in mmap is clunkier than just sharing all in-process memory 
with a bunch of native threads. But the upshot is that it can be a lot 
safer in practice, especially when you have many hands in the pot and 
not much rigor is being taken towards thread safety.

Regarding Chicken threads, as far as I'm aware SRFI-18 threads in 
Chicken are 'green', in that they run on a single native thread and 
cannot avail themselves of additional native threads.

You mention that you've been poking at native threads for a while. Do 
you have a native thread implementation that could be packaged up as an 
egg? I think some people would be eager to try it out, even if its 
incomplete. Maybe this would be a good opportunity to get used to Git 
via a GitHub project? ;)

Thanks,
-Dan