Red Hat Bugzilla – Bug 145981
cpuspeed triggers on disk i/o.
Last modified: 2015-01-04 17:16:04 EST
Description of problem:
cpuspeed inreases cpu frequency when there is a lot of disk i/o. I.e.
when a lot of time is spent in 'waiting'. This causes a lot of wasted
power since disk i/o won't increase just because the cpu is faster
(since that's rarely the bottle neck).
Version-Release number of selected component (if applicable):
are your disks in DMA mode ?
Yes they are.
Running 'dd if=/dev/hda of=/dev/null' puts the cpu in full speed and top reports:
Cpu(s): 3.3% us, 9.3% sy, 0.0% ni, 0.0% id, 85.4% wa, 2.0% hi, 0.0% si
Created attachment 111898 [details]
Patch to measure iowait
This patch gives the desired behaviour.
Modern cpuspeed has this behaviour. Marking as resolved.