Bart Van Assche wrote:
> On Wed, Apr 15, 2009 at 9:19 PM, Pasi Kärkkäinen <> wrote:
>> noop is usually good for the initiator. cfq has a feature (or a bug?) that
>> prevents achieving queue depths deeper than 1, and thus limits your
>> bandwidth a lot when there are (or should be) many ios on the fly at the
>> same time.
> Do you remember on which kernel version you observed the above
> behavior ? This might be a bug in the CFQ scheduler. I found the
> following in the 2.6.28 changelog: "cfq-iosched: fix queue depth
> detection". See also
> or

I do not think we found the root cause. That might be it. I remember 
talking to Aaron Carroll and him sending the attached patch to test. We 
thought the part about the "It should also help alleviate problems 
associated with suboptimal queue-depth detection." was our issue. I see 
the new patch that you referenced also mentioned something about it.

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