Red Hat Bugzilla – Bug 88085
top reports 0% iowait even when disk heavily used
Last modified: 2007-04-18 12:52:47 EDT
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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.
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?
Ah, this is apparently a 2.5.x kernel extension....
indeed, iowait statistics is something in the 2.5 kernel (and RHEL)
it is not present in the standard 2.4 kernel
So, this will be fixed when we move to 2.6.
Yes, indeed it does work if you boot with arjan's test 2.6 kernels.