Dave Chinner wrote:

One thing I just found out - my old *laptop* is 4-5x faster than the
10krpm scsi disk behind an old cciss raid controller.  I'm wondering
if the long delays in dispatch is caused by an interaction with CTQ
but I can't change it on the cciss raid controllers. Are you using
ctq/ncq on your machine?  If so, can you reduce the depth to
something less than 4 and see what difference that makes?

I've been benchmarking on a cciss card, and patched the driver to
control the queue depth via sysfs.  Maybe you'll find it useful...

The original patch was for 2.6.24, but that won't apply on git head.
I fixed it for 2.6.27, and it seems to work fine.  Both are attached.


   -- Aaron