On (01/27/17 13:33), John Fastabend wrote: > > This is an experimental implementation of rx zero copy for af_packet. > Its a bit rough and likely has errors but the plan is to clean it up > over the next few months. > > And seeing I said I would post it in another thread a few days back > here it is.
One question/comment about this: sure, this saves us an skb copy on the rx side, but at least for the Tx side, I think there may be a trade-off between the overhead from the skb setup and the ease of offloading checksum (and UFO where it is available) to consider, even for PF_PACKET. Using PF_PACKET works well for stateless datagram protocols like UDP, and for UDP sockets, we find that just switching to Jumbo (to simulate a poor-man's-UFO) gives us significant improvement in both throughput and latency for our RDBMS workloads - and having the sk_buff facilitates using existing driver-kernel interfaces for offload easily, so while we may gain some perf improvment by shaving of the sk_buff overhead, the trade-off needs to be considered. --Sowmini
