> A user space solution also needs to have the buffer in the
> RAM, otherwise it has to wait for swap instead of read().
> So it may be necessary to lock the user space buffer in RAM.
> Besides, the kernel buffers are freed also when the sound
> device is not used. And the size of the kernel buffer should
> be configurable (like now in ALSA, but on a larger scale).
Yep, but userspace buffers are not physically contiguous, like kernel
sound driver buffers need be (most of the time), and might not even
be needed (or may be smaller).
Example: mp3 player. You can do the buffering on the input side, which
gives you 10 times more "buffer time" with the same amount of RAM than
if you buffer the output of the mp3 decoder.
Also, software modems also need no buffering.
Tom
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