On Tue, 19 May 2020 15:51:56 +0200, Jaroslav Kysela wrote:
Dne 19. 05. 20 v 15:46 Takashi Iwai napsal(a):
Because of these reasons I think it would be better to drop the lock-free implementation entirely and just use the existing non-concurrent architecture-independent implementation from pcm_dmix_generic.c. Aside from being faster, it would also eliminate a lot of architecture-dependent code and inline assembly. Should I submit a patch for this?
The advantage of lockless dmix implementation isn't about its CPU usage but the nature where a stream isn't prevented by other streams, which assures the very low latency, too. That is, with the generic dmix, a stream can be still halted when another stream stalls in the middle, and there is no way to recover from it.
So, IMO, we can start with a dynamic configuration to choose the behavior and add a configure option to choose the implementations. The default behavior should be still an open question, though.
I fully agree here.
OK, I implemented a couple of patches for this.
The default behavior is a bigger question and I chose disabling the lockless for less CPU usage. But it's selectable via configure option or the runtime asoundrc setup (there is already an option dmix.direct_memory_access).
Takashi