On Thu, Jul 26, 2012 at 01:38:03PM -0400, "Xavier R. Gu?rin" wrote:
> > It is the source GID of the local adaptor. Generally you can just use > > index 0, particularly on RoCEE.. > > thanks, this fixed my problem. > > A couple questions: > > is there any overhead associated with using GIDs? Yes, the GRH adds an extra 40 bytes per packet, so it should be avoided on IB. It is mandatory on RoCEE. > man ibv_post_recv tells me that the GRH is written into the first 40 > bytes of the receive buffer for UD QPs. Is that behavior only > restricted to UD QPs, or should I plan the presence of this headers > when using RC QPs ? Yes, only for UD QPs, and the 40 bytes is always reserved for the GRH, even if the packet had none. Jason -- 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
