[LAU] Kxstudio RT kernel vs low latency

[Joakim Hernberg]

On Mon, 28 Jul 2014 23:22:48 +0100
James Stone <jamesmstone at gmail.com> wrote:

> I then removed this and had a poke around in the bios, and found that
> the main culprits for the xruns were C6 mode, and "AMD Power Now".
> Disabling these, and I now have an xrun-free experience with
> frames/period = 32/2 with pulseaudio/jack on my Scarlett 2i4, which is
> pretty amazing for a USB device IMO!

That's very amazing indeed.  But to be sure try to run hackbench too,
and see if it's xrun free under load too.

You can also run jack_iodelay and connect the output to the input on
your soundcard (turn speakers off as it might also produce feedback
depending on how the card is configured).  This ought to tell you the
realworld latency, which many times can be a lot bigger then that given
by buffersizes alone, due to "hidden" hardware buffers and
the delay introduced by the digital to analog conversion itself.

> There was also CPD mode and CState Pmin, which I disabled initially,
> but these don't seem to have any impact on xruns on my system. Cstate
> pmin seems to affect the reported DSP load - but otherwise doesn't
> affect xruns - so I think it's safe to keep on (and maybe is saving
> some power??). CPD mode doesn't seem to have any impact at all.

I suppose you could monitor the cpus temperature and if you see a
decrease in temperature, it most likely corresponds to lower power
consumption.

-- 

   Joakim