Bug 145981 - cpuspeed triggers on disk i/o.
cpuspeed triggers on disk i/o.
Product: Fedora
Classification: Fedora
Component: kernel-utils (Show other bugs)
i386 Linux
medium Severity medium
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Assigned To: Dave Jones
Brian Brock
Depends On:
  Show dependency treegraph
Reported: 2005-01-24 09:44 EST by Pierre Ossman
Modified: 2015-01-04 17:16 EST (History)
1 user (show)

See Also:
Fixed In Version: 1.2.1-1.23_FC4
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2005-10-14 10:04:13 EDT
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oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
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Attachments (Terms of Use)
Patch to measure iowait (1.57 KB, patch)
2005-03-11 12:46 EST, Pierre Ossman
no flags Details | Diff

  None (edit)
Description Pierre Ossman 2005-01-24 09:44:44 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):

How reproducible:
Every time.
Comment 1 Dave Jones 2005-02-12 23:12:43 EST
are your disks in DMA mode ?
Comment 2 Pierre Ossman 2005-02-13 13:27:19 EST
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
Comment 3 Pierre Ossman 2005-03-11 12:46:48 EST
Created attachment 111898 [details]
Patch to measure iowait

This patch gives the desired behaviour.
Comment 4 Pierre Ossman 2005-10-14 10:04:13 EDT
Modern cpuspeed has this behaviour. Marking as resolved.

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