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    SubjectRe: [PATCH 0/3] blkio: IO controller stats
    On Thu, Apr 01 2010, Divyesh Shah wrote:
    > The following series implements some additional stats for IO controller.
    > These stats have helped us debug issues with earlier IO controller
    > versions and should be useful now as well.
    > We've been using these stats for monitoring and debugging problems after the
    > fact as these stats can be collected and stored for later use.
    > One might argue that most of this information can be exported using blktrace
    > when debugging. However, blktrace has non-trivial performance impact and
    > cannot be always turned on. These stats provide a way for continuous monitoring
    > without losing much performance on rotational disks. We've been able to look
    > at these stats and debug issues after problems have been reported in the wild
    > and understand the IO pattern of the affected workloads.
    > Some of these stats are also a good data source for high-level analysis and
    > capacity planning.
    > This patchset adds 4 stats and I will send out another patchset later for
    > stats like io_merged and some stats that can be turned on only for
    > debugging - idle_time (total time spent idling for this blkio_group),
    > wait_time (total time spent by the blkio_group waiting before any one of its
    > queues got a timeslice). I've tried to breakdown the stats and sent the most
    > basic ones here.

    Thanks, I think this makes sense. I've applied it for 2.6.35.

    Jens Axboe

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