Excerpts from Pedro Ribeiro's message of 2010-07-06 13:19:31 +0200: > 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 Ah, nice to hear that the BKL removal is scheduled. Pretty much all I know is that Linus set the BKL removal as precondition for preempt-rt to be merged with mainline. I guess this means that preempt-rt could disappear in some post-.36 version. I won't hold my breath. Anyway, the stock kernel has been good for a while, but there are some cases where I still experience big differences. Some, mostly audio unrelated, actions or kinds of load cause lots of xruns with the stock kernel and none with -rt. Prime example for me is xrandr, enable an external monitor -> xruns, not so with -rt. There are a couple of other cases. It's mostly about this kind of stuff, the achievable latency is pretty much the same in my experience (which is only with an USB interface). -- Regards, Philipp -- "Wir stehen selbst enttäuscht und sehn betroffen / Den Vorhang zu und alle Fragen offen." Bertolt Brecht, Der gute Mensch von Sezuan -- 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
