[paranoia] cpu/system load while ripping from Plextor

[Wolfgang Weisselberg]

Hi, Paul!

Paul Heldens (fr4gg4 at cistron.nl) wrote 24 lines:

> I use an IDE plextor 16/10/40 for ripping trough scsi emulation ( 
> /dev/sr0 ) and it completely drains my system cpu and I/O, to a point 
> where even simple mp3 playback jitters.

Hmmm.

> When burning stuff with it or normal reading , everything is ok, only 
> audio ripping brings my machine to its knees.

That sounds normal (writing is just 'pushing bits in a timely
fashion').   Reading includes error corrections, like
rereading, jitter correction and more.  Also the SCSI
emulation could be a bottleneck -- have a look at a system
monitor (xosview, yamm, omniomni, top, ...) and see which
process eats CPU -- and whether it is 'user' or 'system'
which eats most of the CPU.  Lots of 'system' means the kernel
(probably the emulation) eats the CPU.

> What can I do to prevent this ?

- Find out if it's not the CPU but I/O that is the bottleneck.
  If so, either get another controller for your ripper, i.e.
  make the HD and the CD be on different cables.  IDE is
  notorius for blocking the whole bus (cable) while reading --
  so no other command for another device can be shoved in,
  while the bus is empty and waiting for the HD or cdrom to
  answer the read.
  Or move to SCSI, where 'disconnect' is not only burried in
  the specs but actually implemented.

- nice paranoia.  This could slow it (see other mail)
- un-nice the essential other programs -- if done selective
  and for non-CPU-Hogs this should have less impact than
  giving every other program priority over paranoia.
- in the same direction: Set stable, non-hogging, essential
  programs to 'real time' scheduling.  This gives them
  *absolute* priority, even if they start hogging *everything*
  -- including X.  A simple "while true; do echo "."; done" in
  'real time' scheduling will stop your machine cold out, as
  it's a hog and will leave not a single cycle for someone else.
- Upgrade and use a SMP machine.  paranoia might hog one CPU,
  which leaves you the second one to work on. :-)
- See if your kernel is a good match for your machine.
  Especially if that's the bottleneck.
- Upgrade your ripper to a 'real' SCSI model. :-)
- (Get someone to) find out where exactly the CPU is eaten.
  Fix it.
 
-Wolfgang

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