Re: [PATCH 13/17] scsi: push host_lock down into scsi_{host,target}_queue_ready

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On Thu, 2014-02-06 at 18:10 +0100, Bart Van Assche wrote:
> On 02/06/14 17:56, James Bottomley wrote:
> > Could you benchmark this lot and show what the actual improvement is
> > just for this series, if any?
> 
> I see a performance improvement of 12% with the SRP protocol for the
> SCSI core optimizations alone (I am still busy measuring the impact of
> the blk-mq conversion but I can already see that it is really
> significant). Please note that the performance impact depends a lot on
> the workload (number of LUNs per SCSI host e.g.) so maybe the workload I
> chose is not doing justice to Christoph's work. And it's also important
> to mention that with the workload I ran I was saturating the target
> system CPU (a quad core Intel i5). In other words, results might be
> better with a more powerful target system.
> 

Starting with a baseline using scsi_debug that NOPs REQ_TYPE_FS commands
to measure improvements would be a better baseline vs. scsi_request_fn()
existing code that what your doing above.

That way at least it's easier to measure specific scsi-core overhead
down to the LLD's queuecommand without everything else in the way.

--nab

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