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

[Craig Ringer]

Hi all

I just got a nice new  ATA 48/24/48 CDRW drive, and I'm running into an 
unexpected issue. I can't write at above 24x on my Athlon XP 1.5Ghz 
machine due to the massive load it places on the CPU. Similar issues are 
experienced using cdrecord, cdrdao, readcd, grip (w cdparanoia), and 
other apps. The drive is configured as an IDE-SCSI device.

I have the same problem on another box at work, so its not a 
single-machine issue.

Both are running Debian, sarge at home and woody at work. I've tried the 
  woody 2.4 kernel and also run 2.4.20 (my build) as a matter of course.

Strangely, sometimes I'll do a CD write and it uses near zero CPU time 
like you'd expect with DMA etc. This mainly ocurrs with simple writes of 
.iso files from cdrecord in cooked mode. Using raw mode in cdrecord or 
using cdrdao always places a massive load on the CPU.

So ... this can't be right. I can't reliably write a CD at > 24x on a 
modern fast machine. Anybody have any idea what's going on? My old 8x 
burner wasn't a problem but that could be due to my failure to actually 
notice the CPU load.

I've heard things about issues with the IDE-SCSI interface but didn't 
think it was anything quite this bad. OTOH I've also heard that big 
improvements are due in 2.6 for ATA cdwriters.

Anybody have any idea what's going on?

Craig Ringer