On Wed, May 21, 2008 at 3:20 PM, Ken Restivo ken@restivo.org 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-audi...
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