Hi, On Thu, Mar 12, 2009 at 8:37 PM, Mark Greenwood <fatgerman at ntlworld.com> wrote: > 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. I am sure that this is not the cause. tsched=0 is not passed to module-hal-detect for me, and there's nothing relevant in GConf either. Besides, I recompiled PulseAudio from vanilla sources. Anything that might've been in the Ubuntu configs has been overwritten by the "make install" command. Sean > > 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 >> > _______________________________________________ > pulseaudio-discuss mailing list > pulseaudio-discuss at mail.0pointer.de > https://tango.0pointer.de/mailman/listinfo/pulseaudio-discuss >
