Re: [PATCH 0/3] blkio: IO controller stats

From: Jens Axboe
Date: Fri Apr 02 2010 - 02:45:26 EST

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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