On Thursday 12 March 2009 14:38:18 Sean McNamara wrote: > Hi, > > On Tue, Feb 24, 2009 at 3:36 PM, Lennart Poettering > <lennart at poettering.net> wrote: > > On Tue, 24.02.09 12:20, Jan Claeys (lists at janc.be) wrote: > > > >> > >> Op maandag 23-02-2009 om 15:18 uur [tijdzone -0500], schreef Sean > >> McNamara: > >> > * Once upon a time (old releases, e.g. 7.04 and below?) there was the > >> > -lowlatency kernel flavor. This one went all the way and gave us > >> > CONFIG_HZ=1000 and a fully preemptible kernel (not only voluntary, but > >> > forced preemption). I'm not sure of the rationale for discontinuing > >> > this kernel flavor, but it would be silly to say it's only because of > >> > mirror disk space or something; their disk space consumption has gone > >> > way up since then. > >> > >> Maybe have a look at the -rt kernel? :) > >> > >> (There is a fourth kernel too: -virtual, which is optimized for running > >> in a virtual machine, where the number of hardware to support is much > >> lower than in real machines.) > > > > I cannot say I believe in the -rt kernel. We don't need *that* > > reliable latencies for PA. And given that -rt in real live breaks more > > things than it fixes I don't think it is really worth the effort if > > all you want to do is run PA. > > > > The vanilla kernel is mostly fine for doing multimedia work, even for > > audio production. There's no need to bother with -rt. > > Indeed! And with the Ubuntu -generic kernel, 0.9.15-test* is terribly > glitchy with glitch-free. By rebuilding the same kernel sources using > CONFIG_HZ=1000 and full preemption, rather than CONFIG_HZ=250 and > voluntary preemption, I get *zero* dropouts under a normal desktop > load with the same userspace. > > And the Intel GEM/UXA stuff is fairly CPU intensive at times, > especially scrolling Firefox. That used to glitch like crazy. A simple > tuning of kernel parameters erased this problem. > > Now I can run PA 0.9.15-test without touching the default > configuration at all, and it's very, very good in terms of (lack of) > glitchiness. I've noticed that the latest ubuntu update (on jaunty) has disabled glitch-free mode (tsched=0 passed to module-hal-detect). Are you sure that isn't the cause of the lack of glitches? It certainly is for me, wrong though it sounds. Mark > > I wish I could come up with some quantitative data that demonstrates > clearly how the same kernel sources and userspace stack have wildly > different user experience results with PA. It would be nice to make a > case to the Ubuntu kernel folks to re-introduce the "lowlatency" > kernel flavor. > > BTW, Lennart, last time I ran Fedora I didn't see a "lowlatency" > flavor (or similar) either. Is your default kernel fully preemptible, > or do you have an alternate kernel flavor that is? If not -- it may be > worth considering. At least on my system, full preemption (and > possibly to a lesser degree, CONFIG_HZ=1000) does just the right > things to get latency down to make glitch-free happy. > > Thanks, > > Sean > > > > > Let's keep things in perspective. PA is not a super-ultra-low-latency > > sound server. It's a desktop sound server ... that is all. All I am > > asking for is for latencies not as bad as 210 ms! > > > > Lennart > > > > -- > > Lennart Poettering Red Hat, Inc. > > lennart [at] poettering [dot] net ICQ# 11060553 > > http://0pointer.net/lennart/ GnuPG 0x1A015CC4 > > _______________________________________________ > > pulseaudio-discuss mailing list > > pulseaudio-discuss at mail.0pointer.de > > https://tango.0pointer.de/mailman/listinfo/pulseaudio-discuss > > > _______________________________________________ > pulseaudio-discuss mailing list > pulseaudio-discuss at mail.0pointer.de > https://tango.0pointer.de/mailman/listinfo/pulseaudio-discuss >
