jerks

jerks

[Glenn English]

I'm trying to make a Digital Audio Workstation (DAW) out of a SUN W2100z
(dual AMD64).

Every few seconds, at seemingly random times, everything freezes for
~50ms. Even the mouse. Sometimes. Reliable at the first card moved in
Aisle Riot Solitaire and when Jack is running. Often when I'm typing
email (chars don't get from the keyboard to the screen).

I know that's not much of a description, but I don't know where to start
looking for this. I'm assuming interrupts are being disabled entirely
momentarily. My background says it's time for a bus monitor, but I don't
have one handy.

This happens with a 2.6 kernel from the current updated Sarge or a 2.4
from DeMuDi 1.2.1 distro.

Anybody have any idea how to begin tracing this down? Or maybe a better
explanation of what's going on?

-- 
Glenn English
ghe@slsware.com
GPG ID: D0D7FF20



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Re: jerks

[John Rigg]

On Thu, Dec 08, 2005 at 10:41:47AM -0700, Glenn English wrote:
> I'm trying to make a Digital Audio Workstation (DAW) out of a SUN W2100z
> (dual AMD64).
> 
> Every few seconds, at seemingly random times, everything freezes for
> ~50ms. Even the mouse. Sometimes. Reliable at the first card moved in
> Aisle Riot Solitaire and when Jack is running. Often when I'm typing
> email (chars don't get from the keyboard to the screen).
> 
> I know that's not much of a description, but I don't know where to start
> looking for this. I'm assuming interrupts are being disabled entirely
> momentarily. My background says it's time for a bus monitor, but I don't
> have one handy.
> 
> This happens with a 2.6 kernel from the current updated Sarge or a 2.4
> from DeMuDi 1.2.1 distro.

Could this be the libc NPTL bug? Sarge has a buggy version of glibc with
a broken NPTL implementation (don't know about DeMuDi 1.2.1).
If so, threaded apps won't perform properly - I switched to sid for this
reason.
Workaround is to set LD_ASSUME_KERNEL=2.4.22 for jackd and other audio
apps. In sid it's fixed, and you'll also get the extra benefits of
gcc-4.0's better AMD64 optimisation.

John


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Re: jerks

[Glenn English]

On Thu, 2005-12-08 at 19:31 +0000, John Rigg wrote:

> > This happens with a 2.6 kernel from the current updated Sarge or a 2.4
> > from DeMuDi 1.2.1 distro.
> 
> Could this be the libc NPTL bug? Sarge has a buggy version of glibc with
> a broken NPTL implementation (don't know about DeMuDi 1.2.1).
> If so, threaded apps won't perform properly - I switched to sid for this
> reason.
> Workaround is to set LD_ASSUME_KERNEL=2.4.22 for jackd and other audio
> apps. In sid it's fixed, and you'll also get the extra benefits of
> gcc-4.0's better AMD64 optimisation.

The prospect of sid is terrifying on a machine I'd like to rely on :-)
But I'll try it. Thanks.

DeMuDi, though, runs a 2.4 (.27, I think) and it does the same thing.

-- 
Glenn English
ghe@slsware.com
GPG ID: D0D7FF20



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Re: jerks

[Lee Revell]

On Thu, 2005-12-08 at 12:49 -0700, Glenn English wrote:
> On Thu, 2005-12-08 at 19:31 +0000, John Rigg wrote:
> 
> > > This happens with a 2.6 kernel from the current updated Sarge or a 2.4
> > > from DeMuDi 1.2.1 distro.
> > 
> > Could this be the libc NPTL bug? Sarge has a buggy version of glibc with
> > a broken NPTL implementation (don't know about DeMuDi 1.2.1).
> > If so, threaded apps won't perform properly - I switched to sid for this
> > reason.
> > Workaround is to set LD_ASSUME_KERNEL=2.4.22 for jackd and other audio
> > apps. In sid it's fixed, and you'll also get the extra benefits of
> > gcc-4.0's better AMD64 optimisation.
> 
> The prospect of sid is terrifying on a machine I'd like to rely on :-)
> But I'll try it. Thanks.

This is almost certainly not your problem.  The NPTL bug would not cause
the mouse to freeze for 50ms.

Lee



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Re: jerks

[Lee Revell]

On Thu, 2005-12-08 at 10:41 -0700, Glenn English wrote:
> I'm trying to make a Digital Audio Workstation (DAW) out of a SUN W2100z
> (dual AMD64).
> 
> Every few seconds, at seemingly random times, everything freezes for
> ~50ms. Even the mouse. Sometimes. Reliable at the first card moved in
> Aisle Riot Solitaire and when Jack is running. Often when I'm typing
> email (chars don't get from the keyboard to the screen).
> 
> I know that's not much of a description, but I don't know where to start
> looking for this. I'm assuming interrupts are being disabled entirely
> momentarily. My background says it's time for a bus monitor, but I don't
> have one handy.
> 
> This happens with a 2.6 kernel from the current updated Sarge or a 2.4
> from DeMuDi 1.2.1 distro.
> 
> Anybody have any idea how to begin tracing this down? Or maybe a better
> explanation of what's going on?
> 

Try the -rt kernel and enable latency tracing



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Re: jerks

[David Olofson]

On Thursday 08 December 2005 18.41, Glenn English wrote:
[...]
> Every few seconds, at seemingly random times, everything freezes for
> ~50ms. Even the mouse. Sometimes. Reliable at the first card moved
> in Aisle Riot Solitaire and when Jack is running. Often when I'm
> typing email (chars don't get from the keyboard to the screen).
[...]

This reminds a bit of something I saw when I made some RTAI latency 
tests on the Mini-ITX motherboards we're putting in our rheometers. I 
would get random latency peaks of anything from a few hundred µs 
through tens of ms.

Turns out the integrated ethernet implementation is a slightly broken, 
and has the interface send interrupts to the CPU even if you disable 
it in the BIOS! Linux "handles" it without freezing indefinitely, but 
even RTAI hard RT kernel threads are locked out for a moment every 
now and then.

Solution: I just installed the driver for the NIC!

We use ethernet for communicating with the instruments anyway, but as 
this project haven't been enough of a PITA already, I just *had* to 
test the RT performance *first*, just so I could discover this scare- 
the-h*ll-out-of-control-engineers special feature... :-D


So, bottom line: Never trust "disabled" PCI devices.


//David Olofson - Programmer, Composer, Open Source Advocate

.- Audiality -----------------------------------------------.
|  Free/Open Source audio engine for games and multimedia.  |
| MIDI, modular synthesis, real time effects, scripting,... |
`-----------------------------------> http://audiality.org -'
   --- http://olofson.net --- http://www.reologica.se ---


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