25 Jul
2007
25 Jul
'07
7:25 a.m.
On Wednesday 25 July 2007, Carlo Florendo wrote:
2.4.x kernels are terribly unsuited to do any serious sort of realtime work,
be it audio or midi.
From my experience this is a classification with increasing suitedness for
realtime work:
1] vanilla 2.4.x
2] patched 2.4.x [lowlatency patches]
3] vanilla 2.6.x
4] patched 2.6.x [ingo molnar's realtime preemption patches]
There really should be like 100 bogus places between 2] and 3] and another 100
between unpatched and patched 2.6.x because 2.6.x really is vastly better
than 2.4.x and -rt patched 2.6.x actually is a realtime system which can be
made to work up to microsecond resolution [not millisecond ;)].
Try running
your process with SCHED_FIFO scheduling and a high prio of
e.g. 99.
I've tried that in kernel 2.4 and I get the same latency results. Let me
try tweaking that though by running the system with high priority. The
reason why I'd like to make it work in 2.4 kernels is so that existing
systems with 2.4 kernels could run the app without need for a kernel patch.
Your ideas have been most helpful :)
No problem. BTW: even when you use ALSA queues, the kernel still plays a big
role. Then it's simply ALSA's responsibility to provide good timing and it
basically uses the same mechanisms as a userspace program would.
So thrash 2.4.x for all realtime purposes..
Flo
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