Bug 145981 – cpuspeed triggers on disk i/o.

Bug 145981 - cpuspeed triggers on disk i/o.

Summary:	cpuspeed triggers on disk i/o.

Status:	CLOSED CURRENTRELEASE

Aliases:	None

Product:	Fedora
Classification:	Fedora
Component:	kernel-utils (Show other bugs)
Sub Component:
Version:	3
Hardware:	i386 Linux

Priority	medium Severity medium
Target Milestone:	---
Target Release:	---
Assigned To:	Dave Jones
QA Contact:	Brian Brock
Docs Contact:

URL:
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Keywords:

Depends On:
Blocks:
	Show dependency tree / graph

Reported:	2005-01-24 09:44 EST by Pierre Ossman
Modified:	2015-01-04 17:16 EST (History)
CC List:	1 user (show)

See Also:
Fixed In Version:	1.2.1-1.23_FC4
Doc Type:	Bug Fix
Doc Text:
Story Points:	---
Clone Of:
Environment:
Last Closed:	2005-10-14 10:04:13 EDT
Type:	---
Regression:	---
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Documentation:	---
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Verified Versions:
Category:	---
oVirt Team:	---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---

Attachments	(Terms of Use)
Patch to measure iowait (1.57 KB, patch) 2005-03-11 12:46 EST, Pierre Ossman	no flags	Details \| Diff
Add an attachment (proposed patch, testcase, etc.)

Groups: 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):
2.4-13.1.39

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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