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[RESEND]0x17: Talk, Congestion control architecture for host congestion
by Jamal Hadi Salim 02 Oct '23

02 Oct '23

Apologies, I left out the subject line in the last email, so resending this... Link speeds are going up at an incredible rate. Cloud vendors are already asking for 4-800Gbps. Unfortunately the rest of the host hardware infra is not keeping up. Even at the "low low speed;->" of 100Gbps the host CPU speeds, cache sizes, memory access latency, memory bandwidth per core, NIC buffer sizes, are just overwhelmed. As an example 6 CPU cores can saturate all available memory bandwidth - imagine being on a machine that has 56C(112 hyperthreads).... In this talk, Saksham Agarwal, Arvind Krishnamurthy and Rachit Agarwal say that this has brought in new trends not seen before: congestion within the processor, memory and peripheral interconnects of the host which of course causes back pressure all the way to the NIC - meaning back to the network and, alas, causes congestion within the network. Testing with Linux DCTCP shows that host congestion by our speakers found as much as 1% packet drops at the host, 35-55% throughput degradation, and 120-5000x tail latency inflation! Agarwal et al want us to look closely at more than just network heuristics to resolve this emerging challenge. As an example: applications generating CPU-to-memory traffic and clogging the memory bus are currently not considered as part of the congestion control calculus at all - even though they are most certainly part of the culprits. In this talk our esteemed speakers introduce what they call "hostcc" as a response to these challenges. Hostcc makes about ~800 line kernel code changes. A little bit more details: https://netdevconf.info/0x17/6 For the real meat-and-potatoes come to the talk of course! cheers, jamal PS: 5 more days left for early-bird registration. visit netdevconf.info/0x17/registration

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0x17: Talk,
by Jamal Hadi Salim 02 Oct '23

02 Oct '23

Link speeds are going up at an incredible rate. Cloud vendors are already asking for 4-800Gbps. Unfortunately the rest of the host hardware infra is not keeping up. Even at the "low low speed;->" of 100Gbps the host CPU speeds, cache sizes, memory access latency, memory bandwidth per core, NIC buffer sizes, are just overwhelmed. As an example 6 CPU cores can saturate all available memory bandwidth - imagine being on a machine that has 56C(112 hyperthreads).... In this talk, Saksham Agarwal, Arvind Krishnamurthy and Rachit Agarwal say that this has brought in new trends not seen before: congestion within the processor, memory and peripheral interconnects of the host which of course causes back pressure all the way to the NIC - meaning back to the network and, alas, causes congestion within the network. Testing with Linux DCTCP shows that host congestion by our speakers found as much as 1% packet drops at the host, 35-55% throughput degradation, and 120-5000x tail latency inflation! Agarwal et al want us to look closely at more than just network heuristics to resolve this emerging challenge. As an example: applications generating CPU-to-memory traffic and clogging the memory bus are currently not considered as part of the congestion control calculus at all - even though they are most certainly part of the culprits. In this talk our esteemed speakers introduce what they call "hostcc" as a response to these challenges. Hostcc makes about ~800 line kernel code changes. A little bit more details: https://netdevconf.info/0x17/6 For the real meat-and-potatoes come to the talk of course! cheers, jamal PS: 5 more days left for early-bird registration. visit netdevconf.info/0x17/registration

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0x17: Talk, NIC offloads at Hyperscale: experience, new offloads and validation
by Jamal Hadi Salim 01 Oct '23

01 Oct '23

Willem de Bruijn says that lack of clear operating conditions, vague feature definitions and dearth of publicly available tests makes it hard to deploy at scale NIC offloads from multiple vendors. Issues seen in deployments range from inconsistency between devices, scalability limits, incompatibility with real production workloads, and simply hardware bugs; even a commodity offload as a checksum is not as well defined if you look across multiple vendor implementations. Willem will discuss why providing a way to define these offloads precisely, in a way that scales and avoids common bugs, while combining expertise from multiple vendors and users is the way to go. More importantly he believes that sharing all those details in an open and unencumbered format would help alleviate if not solve the current wild-west approach. The effort is currently housed under the auspices of the "OCP NIC Core Offloads specifications". Willem will go over some critical offloads, from established to novel ongoing work, such as pacing and inline crypto and show how they can fail in practice. And last but not least provide an overview of some of the testcases which have already been contributed to the kernel tree including tests for RSS, HW-GRO, TSO and others. cheers, jamal PS: 6 more days left for early-bird registration. visit netdevconf.info/0x17/registration

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0x17: talk, Improving multi-phy and multi-port interfaces
by Jamal Hadi Salim 01 Oct '23

01 Oct '23

How do we deal with a single MAC connected to multiple PHYs - whether chained or in parallel - with multiple front-facing ports? What about when multiple front facing ports utilizing a single PHY or, fun, multiple PHYs? Maxime Chevallier we have some support for these scenarios today where we hide the PHY behind a netdev. The consequences are there is no way to config an individual PHY when multiple PHYs are present on a link - think SFP transceivers for example. Selecting which front-facing port to use is also limited. In this talk, Maxime will describe ongoing work to support these complex topologies, the challenges faced and expected improvements. cheers, jamal PS: 6 more days left for early-bird registration. visit netdevconf.info/0x17/registration

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0x17: Talk, Is scaling eBPF easy yet? A small step to one server, but giant leap to distributed network.
by Jamal Hadi Salim 30 Sep '23

30 Sep '23

After deploying eBPF for over a year in a distributed service provider production environment Ivan Koveshnikov has come to the conclusion that there are a lot more challenges than simply slicing and dicing packets....What happens on "day 2" after the celebrations ends? In this talk Ivan will discuss important topics: development process, application lifetime management, configuration management and delivery, monitoring and observability, and scaling in the service providers' network. Using eBPF in such an environment adds extra spicing to the process challenges. Come and learn from Ivan's experiences! cheers, jamal Reminder: 6 more days left for early-bird registration. visit netdevconf.info/0x17/registration

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0x17: Power-Aware Network Performance BoF
by Jamal Hadi Salim 30 Sep '23

30 Sep '23

Traditional host Network performance measurements are based on analyzing the correlation between the two classical metrics of throughput and latency against cpu utilization. This approach leaves out an important metric: Power utilization. The huge influx of AI infrastructure - which ends up consuming network resources - has brought much needed attention to power consumption as a variable in network infrastructure. If you consider that the operational cost of power is going up (significantly in some parts of the world with the ongoing crisis) we cannot ignore networking infrastructure contributions to not just the cost factor but also the environmental harm brought forth with high power use. Nabil Bitar, Jamal Hadi Salim and Pedro Tammela feel that Linux, which dominates data center deployments, deserves special attention. There is not much literature or shared experience in this space so they hope to inspire a discussion by sharing their experiences with the community: How would one go about measuring power utilization for network workloads? How do we correlate metrics such as perf, throughput, etc to the power utilized? How would one go about saving power while still achieving an application's stated end goals? If you would like to share your experiences or solutions on this important topic please reach out to me. The agenda is still open. cheers, jamal

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0x17: BoF, Compiler-networking workshop
by Jamal Hadi Salim 28 Sep '23

28 Sep '23

If you thought, as a Linux networking person, that you only needed to sift through the truth^Whype on Rust, CXL, P4, ML/AI then you are mistaken. You also need to learn about compilers!.. Ok, just kidding. But seriously - compilers are the future! In the near future a lot of the networking infrastructure code will be compiler generated. In this exciting workshop, Felipe Alemeida, Tom Herbert, Bala Sambasivam, Neil Turton and Stephan Diestelhorst we will discuss how compilers are developing to accelerate network processing with new techniques, and how essential they are for the higher throughput and flexibility that datacenters need. They will discuss different abstractions for network problems that compilers can leverage to optimize networking and how different abstractions and languages transform to actual programs and instructions for optimal execution on next-generation network devices. Topics include: eBPF compilers, P4 compilers, MLIR, new intermediate representations, data flow analysis, multi-platform support, static analysis, and other advanced topics related to compilers and networking. If you would like to discuss something on this related topic then please reach out to Tom and/or Felipe to be considered for the agenda. cheers, jamal

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0x17: TC workshop
by Jamal Hadi Salim 27 Sep '23

27 Sep '23

Jamal Hadi Salim will chair the classical TC workshop at 0x17. Unicast a request if you have a TC topic you feel is worthy of discussion. Current WAG agenda (subject to update): - The trials and tribulations of attempting to improve the CAKE bufferbloat wars - New TC features requests/improvements - Performance - Test integration progress cheers, jamal

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0x17: BoF, CXL : An overview and applicability to high performance networking
by Jamal Hadi Salim 27 Sep '23

27 Sep '23

If you have not heard of the new 3 letter acronym, CXL(Compute eXpress Link), you will hear a lot more about it in the future. For the uninformed, CXL is an open standard for high-speed, high capacity CPU-to-device and CPU-to-memory connections. At 0x17, Shrijeet Mukherjee will lead a BOF on CXL and it's applicability to networking. Merging the IO and Compute expansion protocols has always been a desired attribute as it allows dis-aggregation of the memory capacity from the compute capacity, and specifically for networking it allows buffer and control state placement to be moved closer to IO and offload devices. If you would like to speak at this BoF on topics covering the state of the art of CXL and the platforms that support it or talk about innovative solutions that CXL enables please reach out to Shrijeet. cheers, jama

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0x17: Rust for Linux Networking Tutorial
by Jamal Hadi Salim 26 Sep '23

26 Sep '23

So you've heard of Rust and you have heard, while walking around the grape vine, about Rust for Linux. You are a hardcore linux kernel hacker and you love your C. You scratch your head as you wonder why in the world would anyone need another language! But at the same time you cant stand all those annoying pesty syzkaller bug reports or CVEs on your code - they take away all the fun. Rust has a key property that makes it very interesting as the second language in the kernel: it guarantees no undefined behavior takes place (as long as unsafe code is sound). This includes no use-after-free mistakes, no double frees, no data races, etc. It also provides other important benefits, such as improved error handling, stricter typing, sum types, pattern matching, privacy, closures, generics, etc. In this tutorial two of the gurus in Rust for Linux, Wedson Almeida Filho and Miguel Ojeda will guide us through a practical example which will use an example of kernel networking code. The sample code is first written in C and then migrated to Rust. Wedson and Miguel will then do a step-by-step walk of the Rust incarnation of the code, explaining how the language works at a high-level and well as giving practical tips to get started with Rust for networking in the kernel. Our esteemed guides will show us how Rust prevents some of the mistakes that could happen in the C version, some of which could become vulnerabilities exploited by bad operators or that pesky syzkaller. There is no prerequisite Rust knowledge needed for this tutorial. cheers, jamal

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