On Mon, Sep 22, 2014 at 1:13 AM, Thomas Graf <tg...@suug.ch> wrote: > On 09/20/14 at 03:50pm, Alexei Starovoitov wrote: >> I think HW should not be limited by SW abstractions whether >> these abstractions are called flows, n-tuples, bridge or else. >> Really looking forward to see "device reporting the headers as >> header fields (len, offset) and the associated parse graph" >> as the first step. >> >> Another topic that this discussion didn't cover yet is how this >> all connects to tunnels and what is 'tunnel offloading'. >> imo flow offloading by itself serves only academic interest. > > We haven't touched encryption yet either ;-) > > Certainly true for the host case. The Linux on TOR case is less > dependant on this and L2/L3 offload w/o encap already has value. > Thomas, can you (or someone else) quantify what the host case is. I suppose there may be merit in using a switch on NIC for kernel bypass scenarios, but I'm still having a hard time understanding how this could be integrated into the host stack with benefits that outweigh complexity. The history of stateful offloads in NICs is not great, and encapsulation (stuffing a few bytes of header into a packet) is in itself not nearly an expensive enough operation to warrant offloading to the NIC. Personally, I wish if NIC vendors are going to focus on stateful offload I rather see it be for encryption which I believe currently does warrant offload at 40G and higher speeds.
Tom > I'm with you though, all of this has little value on the host in > the DC if stateful encap offload is not incorporated. I expect the > HW to provide filters on the outer header plus metadata in the > encap. Actually, this was a follow-up question I had for John as > this is not easily describable with offset/len filters. How would > we represent such capabilities? > > The TX side of this was one of the reasons why I initially thought > it would be beneficial to implement a cache like offload as we could > serve an initial encap in SW, do the FIB lookup and offload it > transparently to avoid replicating the FIB in user space. > > What seems most feasisble to me right now is to separate the offload > of the encap action from the IP -> dev mapping decision. The eSwitch > would send the first encap for an unknown dest IP to the CPU due > to a miss in the IP mapping table, the CPU would do the FIB lookup, > update the table and send it back. > > What do you have in mind? > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
