On Sun, 22.02.09 20:01, Mark Greenwood (fatgerman at ntlworld.com) wrote: > > On Sunday 22 February 2009 19:37:11 Lennart Poettering wrote: > > Heya! > > > > As one result of the alsa-time-test testing (see that last mail of > > mine regarding broken sound drivers) input I got from folks, I learned > > how very different the different distribution kernels actually > > behave. They are much more different than i actually assumed. > > > > <snip> > > Very, very, interesting. > > As someone who has done a fair amount of audio work on Linux I > normally build my own kernel as a matter of course, since none of > them (even the ones that claim to be 'real time') are really up to > the sort of low latency stuff I'm trying to do. (That said, I've > never tried Fedora :) ). I've found it quite possible to achieve > latencies of < 1ms on decent hardware, so yes, 210ms is pathetic :) > On the other hand, that system uses nvidia drivers so I think > they're less of an issue. > > Lennart, are there any definite things that you feel should be built > into a kernel, or any things that definitely should not be in a > kernel, for g-f to work properly? I have a short list of things I've > decided must not be defined in my RT kernels for audio work. I'd be > very interested in doing some experiments with the Mandriva and > Ubuntu setups I'm using because g-f doesn't seem to be working very > well on either of them. Sorry, I am not that much of a kernel developer, so I cannot reliably tell you which options are really a must and whiches ones are not. However, there are some obvious things: HZ=1000 and preempt. Without too much fiddling it should be easy to get a stock kernel with the appropriate config options that does 5ms of latency for the usual cases just fine. Lennart -- Lennart Poettering Red Hat, Inc. lennart [at] poettering [dot] net ICQ# 11060553 http://0pointer.net/lennart/ GnuPG 0x1A015CC4
