Messages in this thread | | | From | Jeff Moyer <> | Subject | Re: [PATCH 1/3] cfq-iosched: Implment IOPS mode | Date | Wed, 21 Jul 2010 16:33:04 -0400 |
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Vivek Goyal <vgoyal@redhat.com> writes:
> o Implement another CFQ mode where we charge queue/group in terms of number > of requests dispatched instead of measuring the time. Measuring in terms > of time is not possible when we are driving deeper queue depths and there > are requests from multiple cfq queues in the request queue. > > o This mode currently gets activated if one sets slice_idle=0 and associated > disk supports NCQ. Again the idea is that on an NCQ disk with idling disabled > most of the queues will dispatch 1 or more requests and then cfq queue > expiry happens and we don't have a way to measure time. So start providing > fairness in terms of IOPS. > > o Currently this primarily is beneficial with cfq group scheduling where one > can disable slice idling so that we don't idle on queue and drive deeper > request queue deptsh (achieving better throughput), at the same time group > idle is enabled so one should get service differentiation among groups.
I like that this is more isolated now. I'm slowly warming up to it. I have one question--just a curiosity, really. What do you see now for the reported sl_used in blktrace when slice_idle is zero and the hardware supports command queueing?
Cheers, Jeff
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