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Re: Burning audio disc literally 30x the system load of data disc



Monty wrote:

Hi folks,

I've found a peculiar behavior in the 2.4.x series (using recent Linux
SG 3.1.2x) that I have to fix one way or another.  I've tried 2.4.20
as shipped by Debian and my hand-built 2.4.21.

In short, I've put together an audio editing workstation to replace
the aging Snotfish. When burning *data* discs, everything is as
expected; I can burn four discs simultaneously at 52x at ~15% total
system load (each burner is on its own busmastering controller... just
in case).  The CD burner buffers have never dropped under 95%.

However, burning *audio* discs, a single audio burn maxes the machine
out at 16x.  Both Athlon 2800+s are near-pegged and the CDROM buffer
regularly empties (here, burn-free keeps saving things).  ps and top
both indicate all the load is in the kernel, and strace shows cdrecord
is using the SG ioctl interface.  I've not yet investigated further,
but I'm about to.  I'm tossing this out hoping someone has a
head-start on the problem.

I think we all agree, especially when demostrated that four 52x data
discs (true 52x at the rim, as reported by cdrecord) work fine, that
one reasonably should expect the same performance burning audio.  Or
at least better than this :-)
No, there is a patch to the 2.4 kernel to use DMA when burning audio, at least for some earlier kernels. I had it in an earlier kernel, but I'm not doing bulk copy for commercial use, so I didn't bother to port it forward. I also noted that with the patch the audio burn on my 20x burner ran at ~48x, both by cdrecord report and actually timing how long it took.

I burn almost all data, so this was of passing interest, I was just making a CD for a car I was using with no tape player.

--
E. Robert Bogusta
 It seemed like a good idea at the time





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