Bug 88085 - top reports 0% iowait even when disk heavily used
Summary: top reports 0% iowait even when disk heavily used
Alias: None
Product: Red Hat Linux
Classification: Retired
Component: procps
Version: 9
Hardware: i386
OS: Linux
Target Milestone: ---
Assignee: Alexander Larsson
QA Contact: Brian Brock
Depends On:
TreeView+ depends on / blocked
Reported: 2003-04-05 12:02 UTC by Michael Young
Modified: 2007-04-18 16:52 UTC (History)
3 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Last Closed: 2003-08-05 09:13:22 UTC

Attachments (Terms of Use)

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.

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