[ofa-general] max_mr limit

[Roland Dreier]

 > I burnt a mem-free f/w on the card and this time I'm getting a different
 > error when trying to set num_mtt to 2097152.

 > I did:

 > modprobe ib_mtcha num_mpt=262144 num_mtt=2097152

 >  kernel: ib_mthca 0000:01:00.0: Failed to initialize memory region table, aborting.

You may not have enough contiguous memory for the buddy allocator
bitmaps for the MTT.  What does /proc/buddyinfo show when this
happens?

 > Roland, when your attempt succeeded were you using a mem-free HCA or the
 > 256MB version?

mem-free.  With the fixes I just posted, I am able to load the driver
with num_mtt=33554432 and have it work in fact.

It's not clear to me why you need such crazy values.  Having 2M MTT
segments means you can map 64GB of memory with 4KB pages... do you
really need that much memory pinned for IB operations?

 - R.