[LAD] Pipes vs. Message Queues

I got curious, so I bashed out a quick program to benchmark pipes vs
POSIX message queues. It just pumps a bunch of messages through the
pipe/queue in a tight loop. The results were interesting:

$ ./ipc 4096 1000000
Sending a 4096 byte message 1000000 times.
Pipe recv time: 6.881104
Pipe send time: 6.880998
Queue send time: 1.938512
Queue recv time: 1.938581

Whoah. Which made me wonder what happens with realtime priority
(SCHED_FIFO priority 90):

$ ./ipc 4096 1000000
Sending a 4096 byte message 1000000 times.
Pipe send time: 5.195232
Pipe recv time: 5.195475
Queue send time: 5.224862
Queue recv time: 5.224987

Pipes get a bit faster, and POSIX message queues get dramatically
slower. Interesting.

I am opening the queues as blocking here, and both sender and receiver
are at the same priority, and aggressively pumping the queue as fast as
they can, so there is a lot of competition and this is not an especially
good model of any reality we care about, but it's interesting
nonetheless.

The first result really has me thinking how much Jack would benefit from
using message queues instead of pipes and sockets. It looks like
there's definitely potential here... I might try to write a more
scientific benchmark that better emulates the case Jack would care about
and measures wakeup latency, unless somebody beats me to it. That test
could have the shm + wakeup pattern Jack actually uses and benchmark it
vs. actually firing buffer payload over message queues...

But I should be doing more pragmatic things, so here's this for now :)

Program is here: http://drobilla.net/files/ipc.c

Cheers,

-dr

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Received on Fri Nov 25 04:15:03 2011