Re: [2.5.70] possible problem with /dev/diskstats

From: Rick Lindsley (
Date: Sun Jun 01 2003 - 14:05:07 EST

    Documentation/iostats.txt says about diskstats:
    Field 9 -- # of I/Os currently in progress
        The only field that should go to zero. Incremented as requests are
        given to appropriate request_queue_t and decremented as they finish.
    But here is a cat /proc/diskstats:
       3 0 hda 948 317 16216 4294408142 90 333 848 7309 4294967294 7309215 4280372198

Yes, I've had a couple of other reports of this. I suspect there is
a path by which an "I/O" appears to have been completed while none was
begun. I've only noticed this on my hda drive as well. What I didn't
notice was exactly when this behavior began, which may have been useful
in tracking down the problem. You'll notice a couple of other values
there in the 4.2 billion range that probably suffer from a similar
(or maybe the same) issue. I haven't seen this on SCSI drives yet,
just hda drives, which suggests there may be something about that I/O
path that bears some closer scrutiny.

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