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Bug 88085

Summary: top reports 0% iowait even when disk heavily used
Product: [Retired] Red Hat Linux Reporter: Michael Young <m.a.young>
Component: procpsAssignee: Alexander Larsson <alexl>
Status: CLOSED DEFERRED QA Contact: Brian Brock <bbrock>
Severity: medium Docs Contact:
Priority: medium    
Version: 9CC: anielsen, riel, wtogami
Target Milestone: ---   
Target Release: ---   
Hardware: i386   
OS: Linux   
Fixed In Version: Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2003-08-05 09:13:22 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:

Description Michael Young 2003-04-05 12:02:37 UTC
From Bugzilla Helper:
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.2.1) Gecko/20030225

Description of problem:
The iowait field in top seems to be stuck at 0.0% even when the machine is under
heavy hard disk load. It looks like what should be reported as iowait is instead
included in the idle figure.

Comment 1 Alexander Larsson 2003-04-07 10:11:44 UTC
Looking at the code it seems top reads the iowait data from the fifth numeric
filed in the /proc/stat cpu line.

However, that field doesn't seem to exist. What's up with this?

Comment 2 Alexander Larsson 2003-04-07 10:15:50 UTC
Ah, this is apparently a 2.5.x kernel extension....

Comment 3 Rik van Riel 2003-07-14 12:45:48 UTC
indeed, iowait statistics is something in the 2.5 kernel (and RHEL)

it is not present in the standard 2.4 kernel

Comment 4 Alexander Larsson 2003-08-05 09:13:22 UTC
So, this will be fixed when we move to 2.6.

Comment 5 Michael Young 2003-08-05 10:03:57 UTC
Yes, indeed it does work if you boot with arjan's test 2.6 kernels.