MTU had no effect, just statistical fluctuations in the test reports. Sorry for misreporting the info.
We are exploiting vectorization as we have a single memif channel per transport socket so we can control the size of the batches dynamically. In theory the size of outstanding data from the transport should be controlled in bytes for batching to be useful and not harmful as frame sizes can vary a lot. But I’m not aware of a queue abstraction from DPDK to control that from VPP. From: Florin Coras <fcoras.li...@gmail.com> Date: Wednesday 9 May 2018 at 18:23 To: Luca Muscariello <lumus...@cisco.com> Cc: Luca Muscariello <lumuscar+f...@cisco.com>, "vpp-dev@lists.fd.io" <vpp-dev@lists.fd.io> Subject: Re: [vpp-dev] TCP performance - TSO - HW offloading in general. Hi Luca, We don’t yet support pmtu in the stack so tcp uses a fixed 1460 mtu, unless you changed that, we shouldn’t generate jumbo packets. If we do, I’ll have to take a look at it :) If you already had your transport protocol, using memif is the natural way to go. Using the session layer makes sense only if you can implement your transport within vpp in a way that leverages vectorization or if it can leverage the existing transports (see for instance the TLS implementation). Until today [1] the stack did allow for excessive batching (generation of multiple frames in one dispatch loop) but we’re now restricting that to one. This is still far from proper pacing which is on our todo list. Florin [1] https://gerrit.fd.io/r/#/c/12439/ On May 9, 2018, at 4:21 AM, Luca Muscariello (lumuscar) <lumus...@cisco.com<mailto:lumus...@cisco.com>> wrote: Florin, Thanks for the slide deck, I’ll check it soon. BTW, VPP/DPDK test was using jumbo frames by default so the TCP stack had a little advantage wrt the Linux TCP stack which was using 1500B by default. By manually setting DPDK MTU to 1500B the goodput goes down to 8.5Gbps which compares to 4.5Gbps for Linux w/o TSO. Also congestion window adaptation is not the same. BTW, for what we’re doing it is difficult to reuse the VPP session layer as it is. Our transport stack uses a different kind of namespace and mux/demux is also different. We are using memif as underlying driver which does not seem to be a bottleneck as we can also control batching there. Also, we have our own shared memory downstream memif inside VPP through a plugin. What we observed is that delay-based congestion control does not like much VPP batching (batching in general) and we are using DBCG. Linux TSO has the same problem but has TCP pacing to limit bad effects of bursts on RTT/losses and flow control laws. I guess you’re aware of these issues already. Luca From: Florin Coras <fcoras.li...@gmail.com<mailto:fcoras.li...@gmail.com>> Date: Monday 7 May 2018 at 22:23 To: Luca Muscariello <lumus...@cisco.com<mailto:lumus...@cisco.com>> Cc: Luca Muscariello <lumuscar+f...@cisco.com<mailto:lumuscar+f...@cisco.com>>, "vpp-dev@lists.fd.io<mailto:vpp-dev@lists.fd.io>" <vpp-dev@lists.fd.io<mailto:vpp-dev@lists.fd.io>> Subject: Re: [vpp-dev] TCP performance - TSO - HW offloading in general. Yes, the whole host stack uses shared memory segments and fifos that the session layer manages. For a brief description of the session layer see [1, 2]. Apart from that, unfortunately, we don’t have any other dev documentation. src/vnet/session/segment_manager.[ch] has some good examples of how to allocate segments and fifos. Under application_interface.h check app_[send|recv]_[stream|dgram]_raw for examples on how to read/write to the fifos. Now, regarding the the writing to the fifos: they are lock free but size increments are atomic since the assumption is that we’ll always have one reader and one writer. Still, batching helps. VCL doesn’t do it but iperf probably does it. Hope this helps, Florin [1] https://wiki.fd.io/view/VPP/HostStack/SessionLayerArchitecture [2] https://wiki.fd.io/images/1/15/Vpp-hoststack-kc-eu-18.pdf On May 7, 2018, at 11:35 AM, Luca Muscariello (lumuscar) <lumus...@cisco.com<mailto:lumus...@cisco.com>> wrote: Florin, So the TCP stack does not connect to VPP using memif. I’ll check the shared memory you mentioned. For our transport stack we’re using memif. Nothing to do with TCP though. Iperf3 to VPP there must be copies anyway. There must be some batching with timing though while doing these copies. Is there any doc of svm_fifo usage? Thanks Luca On 7 May 2018, at 20:00, Florin Coras <fcoras.li...@gmail.com<mailto:fcoras.li...@gmail.com>> wrote: Hi Luca, I guess, as you did, that it’s vectorization. VPP is really good at pushing packets whereas Linux is good at using all hw optimizations. The stack uses it’s own shared memory mechanisms (check svm_fifo_t) but given that you did the testing with iperf3, I suspect the edge is not there. That is, I guess they’re not abusing syscalls with lots of small writes. Moreover, the fifos are not zero-copy, apps do have to write to the fifo and vpp has to packetize that data. Florin On May 7, 2018, at 10:29 AM, Luca Muscariello (lumuscar) <lumus...@cisco.com<mailto:lumus...@cisco.com>> wrote: Hi Florin Thanks for the info. So, how do you explain VPP TCP stack beats Linux implementation by doubling the goodput? Does it come from vectorization? Any special memif optimization underneath? Luca On 7 May 2018, at 18:17, Florin Coras <fcoras.li...@gmail.com<mailto:fcoras.li...@gmail.com>> wrote: Hi Luca, We don’t yet support TSO because it requires support within all of vpp (think tunnels). Still, it’s on our list. As for crypto offload, we do have support for IPSec offload with QAT cards and we’re now working with Ping and Ray from Intel on accelerating the TLS OpenSSL engine also with QAT cards. Regards, Florin On May 7, 2018, at 7:53 AM, Luca Muscariello <lumuscar+f...@cisco.com<mailto:lumuscar+f...@cisco.com>> wrote: Hi, A few questions about the TCP stack and HW offloading. Below is the experiment under test. +------------+ +-----------+ | +-----+ DPDK-10GE| | |Iperf3| TCP | +------------+ |TCP Iperf3 | +------------+Nexus Switch+------+ + |LXC | VPP|| +------------+ |VPP |LXC | +------------+ DPDK-10GE +-----------+ Using the Linux kernel w/ or w/o TSO I get an iperf3 goodput of 9.5Gbps or 4.5Gbps. Using VPP TCP stack I get 9.2Gbps, say max goodput as Linux w/ TSO. Is there any TSO implementation already in VPP one can take advantage of? Side question. Is there any crypto offloading service available in VPP? Essentially for the computation of RSA-1024/2048, EDCSA 192/256 signatures. Thanks Luca
