On Fri, 2014-02-07 at 11:32 +0100, Bart Van Assche wrote: > On 02/06/14 22:58, Nicholas A. Bellinger wrote: > > 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. > > Running initiator and target workload on the same system makes initiator > and target code share CPUs and hence makes it hard to analyze which > performance change is caused by initiator optimizations and which > performance change is caused by interactions between initiator and > target workloads. >
Huh..? There is no 'target workload' involved. All that scsi_debug with NOP'ed REQ_TYPE_FS commands is doing is calling scsi_cmd->done() as soon as the descriptor has been dispatched into LLD ->queuecommand() code. It's useful for determining an absolute performance ceiling between scsi_mq vs. scsi_request_fn() based codepaths without involving any other LLD specific overheads. --nab -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
