Distorted sound on -CURRENT

[Eirik Oeverby]

Robert Watson wrote:
> Just to make sure: you're not running with WITNESS in your kernel, right?
> That adds substantial overhead to every lock operation, and can really
> impact interrupt latency.

No, I'm not using WITNESS - doing so has no effect anyway (I tested).

> Also, you might want to see if your sound device is sharing an interrupt
> with another device that isn't marked MPSAFE, or sharing an interrupt at
> all, which also substantially impacts interrupt latency.  We're working on
> pushing Giant out of various device drivers, but are only partway down
> that road, which might well be the problem.

What's a good way to check that, apart from going through dmesg? I'm 
gonna have to do that tomorrow, so tired I can't focus my eyes properly 
anymore ;)

Thanks,
/Eirik

> 
> Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
> robert at fledge.watson.org      Senior Research Scientist, McAfee Research
> 
> On Wed, 17 Dec 2003, Eirik Oeverby wrote:
> 
> 
>>Hi all,
>>
>>For a long time I have had problems with sound on my ThinkPad, which has
>>a rather sucky Crystal chipset. The problems consist of skips and pops
>>and crackles when playing back audio, and makes it hopeless to listen to
>>any kind of music while working (or playing ;).
>>
>>There have been attempts at fixing this earlier, which has helped
>>somewhat, but I always thought this was a problem on my chipset only -
>>but this does not seem to be the case.
>>
>>I have now tested in a machine that has a SB Live! card (snd_emu10k1
>>module), and I'm experience the same problems, just even more pronounced
>>than with the Crystal chipset.
>>
>>The interesting thing is - this is a non-issue in all 4.x versions of
>>FreeBSD, and it's a non-issue in all other OSes I have tried on the
>>respective computers. I am therefore led to believe there has been some
>>kind of screwup with the PCM or chipset drivers in -CURRENT, or perhaps
>>in some underlying code. This has been a problem atleast since
>>5.1-RELEASE, and I do believe (but cannot confirm) it was a problem with
>>5.0-RELEASE aswell. Choice of scheduler (SCHED_4BSD or SCHED_ULE) has no
>>influence, neither has there been any difference before or after the
>>i386 interrupt code switch.
>>
>>I home someone can have a look at this, it is of minor importance but
>>major annoyance - and personally I think it should be (attempted) fixed
>>before 5.2-RELEASE, if possible. It does make a bad impression on
>>people, even in a FreeBSD-house such as the one I am working for right
>>now.
>>
>>Best regards,
>>Eirik Oeverby
>>
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> 
>