On Mon, Apr 15, 2013 at 2:10 PM, Wendy Cheng <[email protected]> wrote: > Before closing this thread ..... I see there is a clear warning in > IPOIB code that enabling connected mode will cause multicast packet to > drop. I assume this is due to message ordering requirement and the > multicast packet could fall behind the large packet fragment that ends > up causing multicast logic to time out. If my assumption is not > correct, please do kindly correct me.
No, it's because multicasts can't be sent over the RC connections, so they need to be sent via UD. And the datagram size is limited by the underlying IB MTU, which is going to be either 4K or 2K most likely. However if you enable CM and then set your IPoIB MTU to something like 64K, the IP stack will happily create multicast messages bigger than the datagram MTU, and the IPoIB driver really can't do anything with those except throw them away. - R. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
