Re: [Patch 0/5] I/O statistics through request queues

[Jens Axboe]

On Sat, Oct 21 2006, Martin Peschke wrote:
> This patch set makes the block layer maintain statistics for request
> queues. Resulting data closely resembles the actual I/O traffic to a
> device, as the block layer takes hints from block device drivers when a
> request is being issued as well as when it is about to complete.
> 
> It is crucial (for us) to be able to look at such kernel level data in
> case of customer situations. It allows us to determine what kind of
> requests might be involved in performance situations. This information
> helps to understand whether one faces a device issue or a Linux issue.
> Not being able to tap into performance data is regarded as a big minus
> by some enterprise customers, who are reluctant to use Linux SCSI
> support or Linux.
> 
> Statistics data includes:
> - request sizes (read + write),
> - residual bytes of partially completed requests (read + write),
> - request latencies (read + write),
> - request retries (read + write),
> - request concurrency,

Question - what part of this does blktrace currently not do? In case
it's missing something, why not add it there instead of putting new
trace code in?

-- 
Jens Axboe

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