FlexTOE: Flexible TCP Offload with Fine-Grained Parallelism

FlexTOE is a flexible, yet high-performance TCP offload engine (TOE) to SmartNICs. FlexTOE eliminates almost all host data-path TCP processing and is fully customizable. FlexTOE interoperates well with other TCP stacks, is robust under adverse network conditions, and supports POSIX sockets.

FlexTOE focuses on data-path offload of established connections, avoiding complex control logic and packet buffering in the NIC. FlexTOE leverages fine-grained parallelization of the TCP data-path and segment reordering for high performance on wimpy SmartNIC architectures, while remaining flexible via a modular design. We compare FlexTOE on a Netronome Agilio-CX40 to host TCP stacks Linux and TAS, and to the Chelsio Terminator TOE. We find that Memcached scales up to 38\% better on FlexTOE versus TAS, while saving up to 81\% host CPU cycles versus Chelsio. FlexTOE provides competitive performance for RPCs, even with wimpy SmartNICs. FlexTOE cuts 99.99th-percentile RPC RTT by 3.2× and 50\% versus Chelsio and TAS, respectively. FlexTOE's data-path parallelism generalizes across hardware architectures, improving single connection RPC throughput up to 2.4× on x86 and 4× on BlueField.

FlexTOE supports C and XDP programs written in eBPF. It allows us to implement popular data center transport features, such as TCP tracing, packet filtering and capture, VLAN stripping, flow classification, firewalling, and connection splicing.

For more information, please refer to:

• NSDI 22: https://www.usenix.org/conference/nsdi22/presentation/shashidhara
• arXiv: https://arxiv.org/abs/2110.10919

Prerequisites

• Netronome Agilio SmartNICs based on NFP-4000 or NFP-6000 architecture: out-of-tree driver, SDK and Board Support Packages.
• Gigantic (1G) hugepages (>= 1G available memory)
• Linux kernel 4.8.0+

Run

• make to build.

• Setup 1G hugepages. Mount hugetlbfs at /dev/hugepages-1048576kB

  mount -t hugetlbfs -o pagesize=1G none /dev/hugepages-1048576kB
  echo 4 | tee /sys/devices/system/node/node*/hugepages/hugepages-1048576kB/nr_hugepages

• Run

  
  # Load driver
  modprobe uio
  insmod kernel/flextoe_uio.ko

Show supported network devices; Obtain pci_id

./scripts/devbind.py --status

Bind network device to driver

./scripts/devbind.py -b flextoe_uio

Run FlexTOE

./user/flextoe.out

## Usage

Usage: ./user/flextoe.out [OPTION]... --ip-addr=IP[/PREFIXLEN]

Memory Sizes: --shm-len=LEN Shared memory len [default: 1073741824] --nic-rx-len=LEN Kernel rx queue len [default: 256] --nic-tx-len=LEN Kernel tx queue len [default: 256] --app-kin-len=LEN App->Kernel queue len [default: 1048576] --app-kout-len=LEN Kernel->App queue len [default: 1048576]

TCP protocol parameters: --tcp-rtt-init=RTT Initial rtt for CC (us) [default: 50] --tcp-link-bw=BANDWIDTH Link bandwidth (gbps) [default: 40] --tcp-rxbuf-len Flow rx buffer len [default: 8192] --tcp-txbuf-len Flow tx buffer len [default: 8192] --tcp-handshake-timeout=TIMEOUT Handshake timeout (us) [default: 10000] --tcp-handshake-retries=RETRIES Handshake retries [default: 10]

Congestion control parameters: --cc=ALGORITHM Congestion-control algorithm [default: dctcp-rate] Options: dctcp-win, dctcp-rate, const-rate, timely --cc-control-granularity=G Minimal control iteration [default: 50] --cc-control-interval=INT Control interval (multiples of RTT) [default: 2] --cc-rexmit-ints=INTERVALS #of RTTs without ACKs before rexmit [default: 4] --cc-dctcp-weight=WEIGHT DCTCP: EWMA weight for ECN rate [default: 0.062500] --cc-dctcp-mimd=INC_FACT DCTCP: enable multiplicative inc [default: disabled] --cc-dctcp-min=RATE DCTCP: minimum cap for flow rates [default: 0] --cc-const-rate=RATE Constant rate for all flows [default: 0] --cc-timely-tlow=TIME Timely: low threshold (us) [default: 30] --cc-timely-thigh=TIME Timely: high threshold (us) [default: 150] --cc-timely-step=STEP Timely: additive increment step (kbps) [default: 10000] --cc-timely-init=RATE Timely: initial flow rate (kbps) [default: 10000] --cc-timely-alpha=FRAC Timely: EWMA weight for rtt diff [default: 0.020000] --cc-timely-beta=FRAC Timely: mult. decr. factor [default: 0.800000] --cc-timely-minrtt=RTT Timely: minimal rtt without queueing [default: 11] --cc-timely-minrate=RTT Timely: minimal rate to use [default: 10000]

IP protocol parameters: --ip-route=DEST[/PREFIX],NEXTHOP Add route --ip-addr=ADDR[/PREFIXLEN] Set local IP address

ARP protocol parameters: --arp-timeout=TIMEOUT ARP request timeout (us) [default: 500] --arp-timeout-max=TIMEOUT ARP request max timeout (us) [default: 10000000]

Miscellaneous: --fp-poll-interval-app App polling interval before blocking in us [default: 10000] --quiet Disable non-essential logging [default: disabled] --debug-console Enable debug console [default: disabled]