On Tue, Jul 6, 2010 at 4:19 AM, Pedro Ribeiro <pedrib@xxxxxxxxx> wrote: > Hi, > > I've been using -rt kernels since 2.6.29 because I do realtime audio > on my laptop. > > The audio stability has been steadily improving since, and now I find > that I can use 2.6.34 without the -rt patch and achieve the same > stability as 2.6.33-rt - well, my latency requirements aren't that > high, I just need to maintain 8.9ms completely stable, however before > .34 it would be impossible without the -rt patch. > > So out of curiosity, what changed for .34? According to [1], on .33 > Raw Spinlock Annotation was introduced in the mainline kernel. > However, as said above, I can't get the same performance than with > .34. > > I remember that I read somewhere that the one the biggest problems > with latency requirements was the use of the BKL. Do you think there > will be a significant improvement of latency (in specific cases of > course) with the scheduled removal of BKL for 2.6.36? > > Thanks for the help, > Pedro > > [1] http://www.osadl.org/Realtime-Linux.projects-realtime-linux.0.html With my HDSP 9652 and a good quality desktop machine I've been able to achieve <2mS latency for over a couple of years with the standard kernel, but only under controlled setups. If I'm just doing audio and I run nothing else, doing my best to ensure the machine won't jump into some cron job that uses a lot of disk access, etc., then the main line kernel works fine and has for me for quite a long time. In my experience the value of rt-sources is that I don't have to be as careful. I can open a broswer, do a little email, etc., or even build some code and still not get xruns. I cannot do that today with the main line kernel. So, I think it's not that the basic Linux kernel cannot do the job because it can. I suggest it's more about how much extra protection do you want or need? If you've got a machine that's fully dedicated to audio then possibly you could get away with it. If you are using this machine for additional tasks then being able to control real-time priorities will like win out every time. Cheers, Mark -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
