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Re: FIXED: mpt Serious performance issues

On Wed, 9 Feb 2011, Stephan wrote:

probably. But this doesn't mean we can't enable tagged queuing now.
At last for FC it should just work.

The Linux driver also sais TQ is enabled on the SAS drives. As I said,
the adapter doesn´t like that for now. Maybe some queue size
parameters have to be tuned.

This might be the "adapt->adapt_max_periph = maxq" setting in mtp_netbsd.c, if maxq is > 256. The tagging done in the scsipi layer can only deal with 256 tags. I'm not sure how that would affect the mpt(4) driver. I did some work to get ciss(4) to do tagged queueing, and as best I could understand tagged queuing and the ciss driver, it looks like the ciss driver uses it's own tag and is not limited to 256. You could try setting adapt->adapt_max_periph to max(maxq, 256).

Another possibility is that maxq might be incorrectly calculated, but I have no understanding of that part of the mpt driver. I've been curious as to what the actual value of maxq is.

Michael L. Hitch              
Computer Consultant
Information Technology Center
Montana State University        Bozeman, MT     USA

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