Re: [PATCH 2/2] block: account iowait time when waiting forcompletion of IO request

From: Jens Axboe
Date: Fri Feb 15 2013 - 10:45:52 EST

On Thu, Feb 14 2013, Vladimir Davydov wrote:
> Using wait_for_completion() for waiting for a IO request to be executed
> results in wrong iowait time accounting. For example, a system having
> the only task doing write() and fdatasync() on a block device can be
> reported being idle instead of iowaiting as it should because
> blkdev_issue_flush() calls wait_for_completion() which in turn calls
> schedule() that does not increment the iowait proc counter and thus does
> not turn on iowait time accounting.
> The patch makes block layer use wait_for_completion_io() instead of
> wait_for_completion() where appropriate to account iowait time
> correctly.

Thanks, applied both for 3.9 (with Ingos ack).

Jens Axboe

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