Re: [gentoo-user] bad jack(?) performance

[Mark Knecht]

On 10/12/05, Matt Garman <garman@××××××××××.net> wrote:
> On Thu, Oct 06, 2005 at 10:39:44AM -0700, Mark Knecht wrote:
> > 1) First, let's determine whether you need a new kernel. su to
> > ...
> > jackd -R -dalsa -r44100 -dhw -p128 -n2
> > alsaplayer -o jack
> > ...
> > longer test. Any skipping?
>
> Nope, not when running jackd+alsaplayer as root.
>
> However, when running jackd+alsaplayer as a regular user, I get lots
> of skipping.
>
> > If you have skipping at this point then you most likely need a
> > real-time kernel. My 32-bit machines do not. They run fine with
> > gentoo-sources, but my amd64 doesn't run well and needed a new
> > realtime kernel to work right.
>
> FWIW, before posting this message, I followed a jack howto (can't
> remember the exact source), which walked me through recompiling my
> kernel (with "[*] Enable different security models" and "<M>
> Default Linux Capabilities"), as well as installing and setting
> realtime-lsm up correctly...
>
> > 2) Assuming that your tests as root go well, then emerge
> > realtime-lsm.  This may require a new kernel if you don't have the
> > right Linux Securities stuff enabled:
>
> ...but because I'm error-prone, I double-check my configuration.  As
> far as I can tell, I have everything set up correctly.
>
> From what I can tell, it appears that when I run jackd and
> alsaplayer as a non-root user, they automatically get nice'ed, and I
> believe this is what is causing the skipping.
>
> For example, as root:
>
> # ps ax | grep jack
> 9430 pts/1    SLl    0:08 jackd -R -dalsa -r44100 -dhw -p128 -n2

This is good but expected since root canalways access the capabilities
required to run realtime...but...

> 9434 pts/1    SLl    0:09 alsaplayer -o jack

...alsaplayer requires that you say you want to use realtime capabilities:

alsaplayer -r -o jack

This should work better. Give it a try. man alsaplayer for more
options and info.)

>
> # top
>  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
> 9430 root      18   0 28196  27m 2344 S  2.3  2.7   0:08.68 jackd
> 9434 root      15   0 61852  60m 9336 S  2.0  6.0   0:09.89 alsaplayer
>
> But as a regular user:
>
> # ps ax | grep jack
> 9661 pts/11   SNLl   0:00 jackd -R -dalsa -r44100 -dhw -p128 -n2
> 9665 pts/11   SNLl   0:00 alsaplayer -o jack
>
> # top
>
>  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
> 9665 garman    20   5 61868  60m 9336 S  2.0  6.0   0:00.86 alsaplayer
> 9661 garman    22   5 28200  27m 2344 S  1.7  2.7   0:00.82 jackd
>
> Notice the "N" (nice) flag for ps, and the niceness value of 5 in
> top?

Nice should not be necessary.

>
> I even tried invoking jackd with the nice program (e.g. "nice -n 0
> jackd ..."), but still got stuck the result above.
>
> Hopefully I'm missing something simple... any thoughts?
>

Yeah, just the -r most likely. Also, depending on your sound card
128/2 might be a bit tight, but let's try for it and see what happens.

- Mark

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