[openib-general] IPoIB IETF WG presentation updated again

[Roland Dreier]

    Hal> Cloning an AH is probably faster than creating a new one from
    Hal> scratch. (We would need an additional verb for this). How
    Hal> much does this cost ? Is this optimization worth it ?

Actually cloning an AH is probably slower on Tavor than creating one
from scratch, at least if the AH is in Tavor memory.  To clone an AH
one has to do a bunch of reads across PCI and then write the data back
across PCI, while creating a new one is just a matter of taking the
address attributes (which are almost certainly already in CPU cache)
and writing them across PCI.  (Reads across PCI are much more
expensive than writes, which can be posted and even write-combined)

Obviously other HCAs may perform differently.

 - Roland