Re: "mode" and varios processes sharing the same queue for writting

[Eric Wong <normalperson@yhbt.net>]

Iñaki Baz Castillo <ibc@aliax.net> wrote:
> El Viernes, 8 de Enero de 2010, Eric Wong escribió:
> 
> > Yes the mode argument is handled exactly like how the open(2) syscall
> > works (and File.open(), too).
> 
> AFAIK it's not possible to open a queue and change just the maxmsg parameter. 
> Instead all the "attr" fields must be set again.
> And also there is no way to know the system default values (those in 
> /proc/sys/fs/mqueue/*). The only way is by opening (creating in fact) a new 
> mqueue and inspecting its values.

Correct.  POSIX message queues were designed for real-time systems and
one way to help ensure deterministic real-time behavior is to keep
memory preallocated for them.  In-kernel memory is also unswappable, too
(at least under Linux), so you'll never have to wait on disk access.

> > > PS: Thanks a lot for this project, it's exactly what I needed (much
> > > better than using DRb o UNIXsockets) :)
> > 
> > No problem, I'm glad this POSIX feature is getting more exposure :)
> 
> It's really great for me. It works really well by having different writers 
> processes and different reader processes sharing the same mqueue (load 
> balancing out of the box) :)

Good to know, I've yet to test them under high load myself :)

-- 
Eric Wong