extensible way to specify where, how, and when work should happen … including some standard ones: an event loop, portable access to the system execution context, nursery for spawned work4 P2300: STD::EXECUTION them to be treated like a black box. goto is an unstructured control flow construct conditional loop function call goto59 FIRE-AND-FORGET TASK MODELS ARE UNSTRUCTURED Fire-and-forget work is like the result of `task` when both operations complete. // process input in a loop until the user interrupts: sender auto work_loop = unifex::stop_when( unifex::repeat_effect( processInput() ),

Preview 4 Release Candidate Visual Studio 2022 May 2021 Oct 2021 (today) You’re invited Launch Event 🚀 Monday, November 8th, 2021 🚀 8:30 AM PT https://aka.ms/vs2022lau nch Nov 2021 Pain-Free Upgrade available for now under /std:c++latest Visit https://aka.ms/cpp/20 for more details Developer inner-loop C++20 in Visual Studio Build Debug Edit Code Navigation ☑️� Linters ☑️� Colorization integration CMake is a first-class project system in Visual Studio Familiar edit-build-debug inner-loop • including MSVC and Clang-tidy squiggles & quick actions • Doxygen integration Target Windows, Linux

barriers  std::atomic_ref  Designated Initializers  Spaceship Operator <=>  Range-based for Loop Initializer  Non-Type Template Parameters  [[likely]] and [[unlikely]]  Calendars & Timezones used for?  They simplify implementing:  Generators  Asynchronous I/O  Lazy computations  Event driven applications17 Coroutines  C++20 contains language additions to support coroutines  Standard types include support for <=>  vector, string, map, set, sub_match, …  Example:53 Range-based for Loop Initializer  Initializers for switch statements (C++17): struct Foo { int value; int result; };

(*it).first; // K 类型 • (*it).second;// V 类型 map 的遍历：用 C++17 range-based loop • 和 vector 等 STL 容器一样， map 也支持 C++17 的 range-based loop 语法进行遍历 。 • for (auto tmp: m) • 由于刚刚说了， map 真正的“元素类型”是 K-V 对，所以这里的 auto 的定义，里面只有两个成 员： • struct pair { • T1 first; T2 second; • }; map 的遍历：用 C++17 range-based loop • 所以 for (auto tmp: m) 这里 tmp 的类型是 pair 。 • 如果要单独访问 K 或者 V 怎么办？我们看一下 pair 的定义，里面只有两个成 • 要把所有 K 打印出来，就是： • for (auto tmp: m) { • print(tmp.first); • } map 的遍历：用 C++17 range-based loop • 所以 for (auto tmp: m) 这里 tmp 的类型是 pair 。 • 如果要单独访问 K 或者 V 怎么办？我们看一下 pair 的定义，里面只有两个成

from eBPF • No loop support in eBPF verifier (Linux 4.14) • #param unroll • Size limitation of BPF program <= 4096 • Move SNAT allocate port loop into IPVS kernel module • Bounded loop support in Linux Srcport=x Udp for AAAA Srcport=x Udp for A Srcport=x DROP • Solution • In eBPF code, add a loop to wrap port alloc and insert. • If insert fails, it will retry alloc.

nblur 次跳跃，每次跳跃的距离是 nx ，从而 缓存容量需要有 nx*nblur 那么大，才能利用 全部的缓存，而小彭老师的一级缓存只有 32KB 大。 • 因此可以用循环分块（ loop tiling ），将外部 两层循环变为 blockSize 为跨步的，而内部 则在区间 [xBase, xBase + blockSize) 上循环 。 循环分块：用图片来直观感受 BM_y_blur 只有其中一个被用上，不能很好的利用寄 存器资源。 使用 _mm_stream_ps 和 SIMD 指令，加速计算和直写 • 为了充分填满寄存器，我们把 t 循环和 offset 循环交换一下（ loop-interchange ） ，把 offset 换到内层循环去。这样至少能 让四个寄存器同时在进行加法运算（ xmm 寄存器最多有几个来着？总之也不能太多， 不然被编译器 spill 到内存就不好了），从 prefetching • 直写： streaming ， write-through • 延迟隐藏： latency hiding • 陷入空转以等待内存： stall • 循环分块： loop-tiling ， loop-blocking • 寄存器分块： unroll-and-jam ， register-blocking • 寄存器压力： register pressure ， register

vector-like: erase-remove idiom • list-like: remove/remove_if member functions • map-like: handwritten loop calling m.erase(iter) • Many potential hazards 🙀 • remove_if(v.begin(), v.end(), pred); 🐞 • v v.erase(remove_if(v.begin(), v.end(), pred)); 🐞 • Quadratic complexity vec.erase(iter) loop 🐞 • Invalidating iterators while looping 🐞 • Skipping elements while looping 🐞17 Uniform Container Erasure

lots of K8S production practice in Tencent Motivation https://kccncchina2018english.sched.com/event/FuLz/layers-of-isolation-in-kubernetes-tim-allclair-google Kubernetes has many layers of isolation vmm-vcpu: a hypervisor-agnostic abstraction for Virtual CPUs (vCPUs). rust-vmm • event-manager: abstractions for implementing event based systems. • linux-loader: parser and loader for vmlinux and bzImage images

an art Simple diagnostic is a good start Compiler is a teacher/friend [# 100502 Avoid infinite loop in function arguments checking] A trivial fix may require a lot of time ? Fix the bug of next_point

postcondition “Q”. {P} {Q} Logics {True} let x = 10 {x = 10} {x = 3} x += 1 {x = 4} {True} loop {} {False} Hoare Logic Logics P: x ↦ v Ownership We own “x”, and “x” points to “v”. Disjointness