On Wed, May 21, 2008 at 3:20 PM, Ken Restivo <[EMAIL PROTECTED]> wrote:
> > On Wed, May 21, 2008 at 02:23:20PM -0700, Rich E wrote: > > > > > > IIRC, Ubuntu "RT" kernel is not actually Real Time (i.e. with Ingo > > > patches), just a "desktop RT" which is not very useful for audio and > > > certainly not enough for JACK apps of any heft. > > > > > > > Where are you getting this info from? This is not what I have read, but > > maybe I am missing something somewhere. I thought that the Ubuntu kernel > > packagers recently switched to using full realtime preemption... I find > this > > My info is from having installed Ubuntu and used it... but that was a few > years ago. Glad they're using Ingo's patches now. > > > > in the package description of linux-image-2.6.22-14-rt : > > Ingo Molnar's full real time preemption patch (2.6.22.1-rt9) > > > > Here is the output of uname -a: > > Linux pal 2.6.22-14-rt #1 SMP PREEMPT RT Tue Feb 12 09:57:10 UTC 2008 > i686 > > GNU/Linux > > > > .. and here are the kernel settings from cat /boot/config-2.6.22-14-rt | > > grep PREEMPT > > # CONFIG_PREEMPT_NONE is not set > > # CONFIG_PREEMPT_VOLUNTARY is not set > > # CONFIG_PREEMPT_DESKTOP is not set > > CONFIG_PREEMPT_RT=y > > CONFIG_PREEMPT=y > > CONFIG_PREEMPT_SOFTIRQS=y > > CONFIG_PREEMPT_HARDIRQS=y > > CONFIG_PREEMPT_BKL=y > > CONFIG_PREEMPT_RCU=y > > # CONFIG_DEBUG_PREEMPT is not set > > # CONFIG_CRITICAL_PREEMPT_TIMING is not set > > > > Looks realtime to me.. also the latency is really low (5-10ms > > conservatively), much lower than I have experienced on other OS's, with > or > > without realtime. But, if you know something I don't... I have open > ears. > > Nope, you got real-time there, for sure. I was wrong then. > > > Ubuntu runs so nicely on a laptop though... would hate to switch after > > finding such an easy-to-operate linux distribution because pd and only pd > > doesn't like jack in realtime. > > > > Dunno. You're playing Xrun whack-a-mole. Done that; it's not fun. > Ken, this made me laugh for quite a while. Thank you. > > Here's what I did to RT-ify my system (on Debian, but Ubuntu is based on > it): > > http://www.restivo.org/blog/archives/preparing-a-debian-etch-system-for-audio-use > > Also, I expect you know to use chrt to give the IRQ of your audio interface > top priority, higher than JACK and any other process. That's a crucial step. > If I omit that, then I get clicks and pops too, which is why I wrote a > script to do it automatically. You could also install and configure the > "rtirq" package, which works great too. > I had it on my last setup, but for got to do it this time. Thanks for reminding me :) Also, as my other post mentions, I sometimes got clicks with pd even with the script. I actually had to change the irq priority of pd to get rid of them, which is bad since it changes all the threads pd has instead of only the scheduler. I would get "I/O stuck... closing audio" all the time. > > -ken >
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