On Fri, Apr 21, 2006 at 11:25:21AM +0200, Sebastien Godard wrote:
> Because of a Linux kernel bug, iostat -x may display huge I/O response times
> (svctm) and a bandwidth utilization (%util) of 100% for some devices. Indeed
> these devices have a value for the field #9 (beginning after the device
> name)
> in /proc/{partitions,diskstats} which is always different from 0, and even
> negative sometimes. Yet this field should go to zero, since it gives the
> number of I/Os currently in progress (it is incremented as requests are
> submitted, and decremented as they finish).
Yep, this seems to be the case. It seems that some requests decrement
in_flight multiple times so it goes negative pretty quickly.
> To (temporarily) solve the problem, you should reboot your system to
> reset the
> counters in /proc/{partitions,diskstats}.
That does not help, by the time the boot process finishes in_flight is
already negative.
Gabor
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