P4, EPBF, and Linux TC Offload
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The webinar discussed accelerating P4 and eBPF programs on Netronome SmartNIC hardware. It covered the Linux kernel infrastructure like TC and XDP that supports offloading eBPF programs. It also explained how the NFP architecture is optimized for network flow processing with its multi-core design and memory hierarchy. The webinar demonstrated how eBPF programs can be translated to run efficiently on the NFP hardware by handling maps and applying optimizations.
P4, EPBF, and Linux TC Offload
- 1. 1©2016 Open-NFP Open-NFP Summer Webinar Series: Session 4: P4, EBPF And Linux TC Offload Dinan Gunawardena & Jakub Kicinski - Netronome August 24, 2016
- 2. 2©2016 Open-NFP Open-NFP www.open-nfp.org Support and grow reusable research in accelerating dataplane network functions processing Reduce/eliminate the cost and technology barriers to research in this space • Technologies: – P4, eBPF, SDN, OpenFlow, Open vSwitch (OVS) offload • Tools: – Discounted hardware, development tools, software, cloud access • Community: – Website (www.open-nfp.org): learning & training materials, active Google group https://groups.google.com/d/forum/open-nfp, open project descriptions, code repository • Learning/Education/Research support: – Summer seminar series, P4DevCon conference, Tutorials (P4 Developer Day), research proposal support for proposals to the NSF, state agencies Summer seminar series to further progress to our objective. Present applied reusable research.
- 3. 3©2016 Open-NFP Universities Companies P4DevCon Attendees/Open-NFP Projects* *This does not imply that these organiza4ons endorse Open-NFP or Netronome
- 4. 4©2016 Open-NFP Session Agenda 1. Introduction – Objectives 2. Overview: The high level model for offload - What we are offloading – P4 / eBPF - Overall programmer model for transparent offload 3. Linux Kernel Infrastructure – The Traffic Classifier (TC) – eXpress Data Path (XDP) – Current eBPF translation on X86/ARM64/PPC64 4. Hardware Intro to NFP (Network Flow Processor) architecture – SmartNICs-Multi Core, Many Core – NUMA, Memory Hierarchy 5. Accelerating P4/eBPF in NFP : Implementation – Kernel core infrastructure – Map handling in the kernel – Translating instructions – Basic Map Support – Optimizations 6. & 7. Demo; Summary
- 6. 6©2016 Open-NFP Introduction: Objectives Understanding how eBPF is relevant to P4 Understanding the support for offload and state of art in the Linux Kernel The Code – Understand the structure of a eBPF program – Gain an insight into how this is translated and executed in hardware Understanding how the NFP architecture on the Agilio CX enables high performing, fully programmable network offload – The Many Core architecture and its advantages
- 7. 7©2016 Open-NFP Overview: High level model for offload • What we are offloading – P4 / eBPF • Overall programmer model for transparent offload
- 8. 8©2016 Open-NFP P4 and eBPF What are P4 and eBPF? Domain specific languages for specifying forwarding behaviour of the data plane of network components P4 - Programming Protocol-Independent Packet Processors • Header format description • Parse Graphs (FSM) • Tables (<keys,actions>) • Actions manipulate packet header/metadata • Control flow – an imperative program, describing sequence of data dependent match/actions eBPF – Extended Berkley Packet Filters • Low level (machine code like) language • Code executed by a VM (restricted memory, no sleeps/locks, limited API to kernel)in the Kernel (TC) • Code injected into netfilter hook points in kernel data plane • Maps (<key, value> stores) • Chained filter functions • Match/action • Static verification of safety, guaranteed to terminate
- 9. 9©2016 Open-NFP Translating P4->eBPF John Fastabend P4 to eBPF compiler Why translate P4 to eBPF? Table and diagrams © Mihai Budiu
- 10. 10©2016 Open-NFP Model for Transparent Offload Programmer / user is “unaware” that eBPF code is “offloaded” Requirements • Partial pipeline offload • Fallback to software for any eBPF code block • Transparent user mode / kernel mode access to tables eBPF Program 2 (HW offload) eBPF Program 3 Packet In eBPF Program 1 (HW offload) PCI-E crossing
- 11. 11©2016 Open-NFP Linux Kernel Infrastucture • The Traffic Classifier (TC) • eXpress Data Path (XDP)
- 12. 12©2016 Open-NFP Linux Traffic Classifier (TC) Component Linux Component Shaping The class offers shaping capabili4es Scheduling A qdisc acts as a scheduler e.g. FIFO Classifying The filter performs classifica4on through a classifier object. Policing A policer performs policing within a filter Dropping The “drop” ac4on occurs with a filter+policer Marking The dsmark qdisc is used for marking eBPF program TC diagram and example program © Jamal Hadi Salim
- 13. 13©2016 Open-NFP eXpress Data Path (XDP) What • High performance, programmable network data path Utility • Useful for packet processing • forwarding • load balancing • DOS mitigation • firewalls, etc. XDP architecture diagram © Tom Herbert
- 14. 14©2016 Open-NFP Hardware Intro to NFP (Network Flow Processor) architecture • NUMA, Memory Hierarchy • Current eBPF translation on X86/ARM64/ PPC64
- 15. 15©2016 Open-NFP NUMA, Memory Hierarchy Architecural Philosopies: • Bring the data close to where it needs to be processed • Facilitate highly concurrent access to memories • Mitigate branch costs and hide I/O & memory access latencies
- 16. 16©2016 Open-NFP Current eBPF translation on X86/ARM64/PPC64 1) Write eBPF program as a simple C Program 2) Compiled to eBPF byte code 3) Loaded into the Linux TC 4) Run through verifier 5) Cross compiled to X86/ARM64/PPC64 … Or now NFP Byte Code! NFP hardware offloaded eBPF TC
- 18. 18©2016 Open-NFP Supported Actions User Space Traffic Classifier (TC) Driver (XDP) Firmware & Hardware PCI-E Network Kernel User NFP TCP Stack Packet + Descriptor, Meta data Packet + Sk_Buf Supported Ac2ons • Drop • Mark • Redirect Redirect Drop Mark
- 19. 19©2016 Open-NFP Accelerating P4/eBPF in NFP : Implementation • Kernel core infrastructure • Map handling in the kernel • eBPF to NFP • Map Support • Optimizations
- 20. 20©2016 Open-NFP Kernel core infrastructure User Space Traffic Classifier (TC) Driver (XDP) NFP Offload Control eBPF Program + Flags Firmware & Hardware PCI-E Network Kernel User NFP TCP Stack skip_sw | skip_hw Offload obj Stats
- 21. 21©2016 Open-NFP eBPF to NFP eBPF Registers 10 x 64bits MAP DRAM X X X X A B 16 x 2 x 32bits ME Registers Translate Communica4on Registers NFP • Non-linear mapping • 32 bit translation
- 22. 22©2016 Open-NFP • Write interception • Ownership • Associating with a device • Read-Only single-user maps • Read-Only multi-user maps • Write-Enabled single-user maps • Write-Enabled multi-user maps Map Handling in Kernel & Map Write Reflection User Space Network MAP Kernel Space NFP MAP Write Reflec4on PCI-E Control Applica4on
- 23. 23©2016 Open-NFP Optimizations • Dealing with different memory types • Peephole Optimizer • Dropping unnecessary jumps • Optimizing instructions with immediates • Fusing instructions • Full A/B register allocations • Liveness analysis with real state size tracking
- 25. 25©2016 Open-NFP Summary • Learnt the relationship between P4 and eBPF • Discovered the infrastructure in the Linux Kernel for eBPF offload • Learnt about how the Netronome Smart NIC architecture is optimised for network flow processing • Explored how we implemented the eBPF offload in hardware
- 26. 26©2016 Open-NFP QUESTIONS? Dinan Gunawardena dinan.gunawardena@netronome.com Jakub Kicinski Jakub.Kicinski@netronome.com