Linux has supported a large number of SMP systems based on a variety of CPUs since the 2.0 kernel. Linux has done an excellent job of abstracting away differences among these CPUs, even in kernel code. One important difference is how CPUs allow memor…

Memory ordering - Wikipedia https://en.wikipedia.org/wiki/Memory_ordering https://zh.wikipedia.org/wiki/内存排序 内存排序是指CPU访问主存时的顺序.可以是编译器在编译时产生,也可以是CPU在运行时产生.反映了内存操作重排序,乱序执行,从而充分利用不同内存的总线带宽. 现代处理器大都是乱序执行.因此需要内存屏障以确保多线程的同步. 目录 1编译时内存排序 1.1编译时内存屏障 2运行时内存排序…

A method includes storing, with a first programmable processor, shared variable data to cache lines of a first cache of the first processor. The method further includes executing, with the first programmable processor, a store-with-release operation,…

A method and apparatus for preserving memory ordering in a cache coherent link based interconnect in light of partial and non-coherent memory accesses is herein described. In one embodiment, partial memory accesses, such as a partial read, is impleme…

Memory Ordering   Background 很久很久很久以前,CPU忠厚老实,一条一条指令的执行我们给它的程序,规规矩矩的进行计算和内存的存取. 很久很久以前, CPU学会了Out-Of-Order,CPU有了Cache,但一切都工作的很好,就像很久很久很久以前一样,而且工作效率得到了很大的提高. 很久以前,我们需要多个CPU一起工作,于是出现了传说中的SMP系统,每个CPU都有独立的Cache,都会乱序执行,会打乱内存存取顺序,于是事情变得复杂了…… Problem 由于每个CP…

如果不使用任何同步机制(例如 mutex 或 atomic),在多线程中读写同一个变量,那么,程序的结果是难以预料的.简单来说,编译器以及 CPU 的一些行为,会影响到程序的执行结果: 即使是简单的语句,C++ 也不保证是原子操作. CPU 可能会调整指令的执行顺序. 在 CPU cache 的影响下,一个 CPU 执行了某个指令,不会立即被其它 CPU 看见. 利用 C++ 的 atomic<T> 能完成对象的原子的读.写以及RMW(read-modify-write),而参数 std::m…

What is RCU, Fundamentally? https://lwn.net/Articles/262464/ If you can fill the unforgiving secondwith sixty minutes worth of distance run,“Highly scalable” your code will be reckoned,And—which is more—you'll have parallel fun! With apologies to Rud…

[摘要]编译器保证volatile自己的读写有序,但由于optimization和多线程可以和非volatile读写interleave,也就是不原子,也就是没有用.C++11 supposed会支持atomic operation. ---------------------------------------------^C^V的分割线---原帖在这里-------------------------------------------------------------- 这篇文章详细剖析…

Methods and apparatus to provide for power consumption reduction in memories (such as cache memories) are described. In one embodiment, a virtual tag is used to determine whether to access a cache way. The virtual tag access and comparison may be per…

ROM Read-only memory (ROM) is a class of storage medium used in computers and other electronic devices. Data stored in ROM can only be modified slowly, with difficulty, or not at all, so it is mainly used to distribute firmware(software that is very…