On Sun, 02 Jul 2000, Jeff Garzik wrote:
> On Sun, 2 Jul 2000, Paul Barton-Davis wrote:
> > If linux kernel folk were willing to install the hardware necessary to
> > run the "real" programs, I could point them to dozens of them in an
> > instant, all of which would fail when configured for low latency. But
> > they are not (which is just fine), and so we have to use "benchmarks"
> > to demonstrate just how messed up things are.
>
> Can you give list a setup, or setups, that can be used to show low
> latency for specific usage cases?
>
> I'm concerned that the latencies you are seeing, in some cases, may
> be due to the fault of the sound driver not the inherent slowness of
> the operating system.
Of course I thought about this:
that's why I included a version which uses only RTC in the
latencytest package. (notice that it uses aync SIGIO notifications
which are not in 2.2 by default (2.4 contains the RTC SIGIO patch) )
here you see a RTC latencytest using a 2048HZ RTC frequency
(lowlatency kernel)
http://www.gardena.net/benno/linux/audio/rtc2048-cpu80/2048.html
as you can notice the max latency drift is about 500usecs under high
load.
no soundcard , no ALSA installed nothing, all you need is the RTC clock.
This is to cut out any disturbing issue, (like potential flaky
sounddrivers),
but trust me the problem _IS_ the scheduling.
BTW: I should really rewrite latencytest (it was a quick hack)
from scratch in order to include RTC using blocking reads and other interesting
stuff I have in mind, hopefully before the next century.
>
> I'm a linux kernel folk, and I've got some test hardware, now I'm
> waiting for the rhetoric to die down and the real info to start
> flowing. :)
nice.
can you tell use what you want to investigate in particular ?
Benno.
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