[plug] massive CPU activity on CD writing, cdda rips, etc

[Craig Ringer]

> Hrm, I have an 8x CD burner and it takes up about 30% cpu time on my
> 800MHz Duron with DMA disabled.  With DMA enabled, the machine locks
> hard a couple of minutes after you try to use it :(  It's not a hardware
> problem, the drive works fine in Windows with (almost) no CPU load
> and DMA enabled.

hdparm -d /dev/hdc	
/dev/hdc: No such file or directory
hdparm -d /dev/sr0
/dev/sr0 not supported by hdparm

if its using DMA (must be sometimes to get the near-zero-CPU-time 48x 
writes I can get in cooked TAO mode using cdrecord), I can't control 
when or how.

The problem is that it appears to use DMA - SOMETIMES. So I don't know 
what write speeds are safe for a given write, since its somewhat 
inconsistent to say the least. Its also a PITA as I'm re-ripping my CD 
collection as q7 ogg (~200kbps) and the ripping munches 70%+ of my 
athlon machine's CPU power. Why 200kbps ogg? well, I got new 
headphones.... and suddenly 128kbps mp3 sounded awfully nasty.

Craig