HighPerformanceP4SoftwareSwitch [FreeBSD WIKI]

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====== High Performance P4 Software Switch ======
  * Student: [[/YuriIozzelli|YuriIozzelli]] (y.iozzelli@gmail.com)
  * Mentor:  [[/LuigiRizzo|LuigiRizzo]] (luigi@freebsd.org)

===== Project description =====
Software switches are a key component of any cloud infrastructure, and even proposal focused on hardware targets, such as P4 ([[http://p4.org]]), cannot ignore software implementations and their performance.

Historically, software packet processors have been limited in performance by network I/O, but this is no more true with high speed frameworks such as netmap and DPDK.

In this project I would like to implement a modified version of the reference p4 switch ([[https://github.com/p4lang/behavioral-model]]) on %%FreeBSD%%, which uses netmap for faster packet I/O: the goal would be reaching the 1 Mpps order-of-magnitude speed (current reference implementation is limited to 150 Kpps for a simple l2 switch with 2 hosts).

This would enable P4 to be used in fast networking experimens as well as real environments.

===== Approach to solving the problem =====

The required steps would include:

  * Develop a simplified p4 target wich uses netmap as a backend for packet I/O (current implementation uses pcap)
  * Optimize the target performance leveraging both standard techniques (e.g. limit memory allocations by re-using buffers, use of a more parallel architecture) and netmap-enabled techniques (e.g. batching I/O)
  * Reach feature parity with the reference switch target, and have a functional openflow-enabled demo, which will be used to evaluate performance vs the reference implementation and others software switch solutions

===== Deliverables =====

==== D1 ====

Port the existing reference implementation code to %%FreeBSD%%. Develop a simplified
P4 switch target which replaces pcap with netmap for packet I/O.

==== D2 ====

Now that the I/O is faster, find the new bottlenecks and address them. I will
probably need to modify the target to use pre-allocated buffers for packets and
process packets in multiple threads in a pipeline, and try to keep synchronization costs low.

==== D3 ====

Extend the version developed to support more advanced features used by common
p4 programs (packet replication, learning, multicast groups), and evaluate the
performance vs the reference implementation.

==== D4 ====

Develop an extended demo which implement the openflow protocol on top of the
developed target, and evaluate the performance vs the reference implementation
and other openflow software switches.

===== Milestones =====

This is the expected timeline with the milestones, with the actual work done added by linking to relevant soc-status mailing list posts.

  * 23 – 29 May: port the existing code to %%FreeBSD%% --> [[https://lists.freebsd.org/pipermail/soc-status/2016-May/000972.html|1]]
  * 30 May - 5 June: add netmap-enabled I/O to a simple P4 target (D1)--> [[https://lists.freebsd.org/pipermail/soc-status/2016-June/000981.html|1]]
  * 6 – 12 June: optimize memory management --> [[https://lists.freebsd.org/pipermail/soc-status/2016-June/000987.html|1]]
  * 13 – 19 June: perform multithreading processing of packet in a pipeline (D2) --> [[https://lists.freebsd.org/pipermail/soc-status/2016-June/000993.html|1]]
  * 20 – 26 June: Prepare for mid-term evaluation: clean code and write results report --> [[https://lists.freebsd.org/pipermail/soc-status/2016-June/000999.html|1]]
  * 27 June - 17 July: Extend the target to support replication, learning and multicast --> [[https://lists.freebsd.org/pipermail/soc-status/2016-July/001006.html|1]], [[https://lists.freebsd.org/pipermail/soc-status/2016-July/001022.html|2]]
  * 18 – 31 July: Evaluate and possibly improve performance (D3) --> [[https://lists.freebsd.org/pipermail/soc-status/2016-July/001027.html|1]], [[https://lists.freebsd.org/pipermail/soc-status/2016-August/001032.html|2]]
  * 1 – 14 Aug: Develop the openflow demo and measure performance (D4) --> [[https://lists.freebsd.org/pipermail/soc-status/2016-August/001038.html|1]], [[https://lists.freebsd.org/pipermail/soc-status/2016-August/001042.html|2]]
  * 15 – 23 Aug: clean code, improve documentation and report final speed measurements

===== End of GSoC: State of the Project =====

I successfully implemented D1 and D2, improving the performance of the target by 2x-4x (depending on the p4 program).

Deliverable D3 was about improving the performance of advanced features like multicast and learning, but after many tries I didn't obtain significant speedup.
The existing implementation is of course compatible with the improvements introduced by D1 and D2.

In order to allow the simple_switch target to use the newly developed lockless queue, I had to adapt it to more advanced behaviors like rate limiting and multiple producers
(my original lockless queue was single producer, single consumer), so I used the time allocated for D3 to do that.

I couldn't set up the openflow demo for a performance comparison because i ran out of time (I lost almost two week because this summer I also had my thesis dissertation).
I still have more basic performance comparisons that show the improvements.

The project as of now is structured this way:

  * [[https://github.com/zarghul/behavioral-model/tree/gsoc-master|A gsoc-master branch]], with all the experimental modifications to the codebase, and a speed_tests directory with some scripts to measure performance. It also have a new target (called fast_switch), which uses the new queue classes. Netmap device manager is available to all the targets with the option --enable-netmap
  * [[https://github.com/zarghul/behavioral-model/tree/gsoc-dev-manager-netmap|a gsoc-dev-manager-netmap branch]], which contains only the netmap-related code. The commits are squashed and I plan to use it for a pull request to the upstream repository. The netmap support is enabled by the configure script with the parameter --enable-netmap.
  * [[https://github.com/zarghul/behavioral-model/tree/gsoc-lockless|a gsoc-lockless branch]], which only contains the lockless queue related code. The commits are squashed and I plan to use it for a pull request to the upstream repository
  * [[https://github.com/zarghul/freebsd_ports|a new repository: freebsd_ports]]. This contains the Makefiles and the patches necessary to build the software on freebsd. I also needed to port a couple other projects that are dependencies. As of now, the port builds version 1.2.0 of the vanilla upstream code. If the above pull requests will be accepted, I plan to update the version in the Makefile. If they will not be accepted, I could use my own github repo, or leave to the user the choice of what features use.

==== How to test the improvements ====

To test the fast_switch target performance (which includes all the festures):
  * checkout the gsoc-master branch
  * configure and compile with -O3 level of optimization
  * go to the ''%%speed_tests%%'' directory
  * see the help for available options
  * (the virtual ethernet tests only work on linux, because they create veth pairs. It should be easy to use an epair instead)

===== The Code =====

  * https://github.com/zarghul/behavioral-model relevant branches are named gsoc-*
  * https://github.com/zarghul/freebsd_ports

===== Useful links =====

  * [0] http://info.iet.unipi.it/~luigi/netmap/
  * [1] http://p4.org
  * [2] https://github.com/p4lang/behavioral-model