8 Jun
2006
8 Jun
'06
3:10 p.m.
[Paul Davis]
On Wed, 2006-06-07 at 11:12 +0300, Jussi Laako wrote:
actually, according to my copy of
/usr/src/linux/ipc/mqueue.c
and
http://laurel.datsi.fi.upm.es/web/cgi-bin/man/man2html?7+mq_overview
linux takes us out of the posix stone age and implements the poll
syscall on message queues (which are simple file descriptors to a
linux application). thanks kernel guys!
portability questions aside, it remains the question whether mqd_t is
significantly faster than an ordinary pipe when used with poll().
cheers, tim
Paul Davis wrote:
nice to hear that they are faster. on the other hand, once again POSIX
screws us all over by not integrating everything into a single blocking
wait call. i've said it before, i'll say it again - this is one of the
few things that the win32 API gets right - you can block in one call on
almost *anything*. AFAICT, you cannot select/poll on a msg queue. writing to a pipe is not 100% RT safe, but if the
pipe is created in a
shm filesystem, its as close to it as you will get without ...
Nowadays, there's also available a very good interface from POSIX RT
extensions; posix message queues. See mq_send(3). You can use either
mq_receive(3) or mq_notify(3) for reception of the message.
I also measured posix message queues to be about twice as fast as for
example local (unix) sockets.
Now that Linux systems generally are pretty close to full POSIX
(IEEE-1003.1) compliance, I don't see any reason why not to make
advantage of it.