On Thu, Jun 14, 2012 at 08:24:35AM -0700, Pradeep Satyanarayana wrote: > With these minimal changes IPoIB throughput reached between > 19-20Gb/s with just 2 threads. This was really unexpected. Given > that, we wanted to revisit the usage of checksums in IPoIB. > So, it looks worthwhile to allow for 'checksum-less' IPoIB-CM within > a cluster on a single subnet. From a checksum perspective, this > would be no different from RDMA. What are your thoughts?
There have been discussions around a 'checksum-less' IPoIB operation for a little while. The basic notion was to enable the checksum offload mechanism, pass the information from Linux for offload straight through to the other side (eg via an extra header or something), have the other side reconstruct the offload indication on RX and inject back to into the net stack. This would be similar to the way checksum bypass works in virtualization (Xen/KVM) where the virtualized net TX just packages the offload data and sends it to the hyperviser kernel which then RX's it and restores the very same checksum offload information. During the CM process this feature would be negotiated. I don't think anyone ever made patches for this, but considering the performance delta you see it really seems worthwhile. 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
