[Debburn-devel] Wodim wakeups reported by PowerTOP

[Peter Samuelson]

[Alberto Gonzalez]
> I've noticed that while burning a CD in K3b PowerTop reports about 50
> wakeups per second caused by wodim.

I'm guessing this is wodim keeping the FIFO full.  You don't want a
pipeline stall where the CD writer has finished writing its data and
has to sit and wait for more.  Modern burners can handle it ("burnfree"
mode) but not all burners can, and apparently even modern burners
produce somewhat lower quality discs when they have to invoke this
functionality.

In theory if your CD burner has a large enough buffer, we could poll it
less often to see how full the buffer is.  But you still want to leave
enough safety margin for reading from a busy hard disk, marginal disk
block, congested network share.  We have real-time requirements and a
non-real-time OS environment, so we have to do the best we can.

> but still I wonder if it couldn't be improved. Does burning a CD
> require all those wakeups?

On the other hand ... by the time you've cranked the CD motor up to 52x
and lit the "burn" laser, does the power use by the CPU still matter?
-- 
Peter Samuelson | org-tld!p12n!peter | http://p12n.org/