Satisfying memory ordering requirements between partial reads and non-snoop accesses

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Satisfying memory ordering requirements between partial reads and non-snoop accesses

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 in Modern Microprocessors

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…

Multi-core compute cache coherency with a release consistency memory ordering model

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,…

memory ordering 内存排序

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…

Memory Ordering （注意Cache带来的副作用，每个CPU都有自己的Cache，内存读写不再一定需要真的作内存访问）

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…

C++ atomic 和 memory ordering 笔记

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…

Snoop resynchronization mechanism to preserve read ordering

A processor employing a post-cache (LS2) buffer. Loads are stored into the LS2buffer after probing the data cache. The load/store unit snoops the loads in the LS2 buffer against snoop requests received from an external bus. If a snoop invalidate requ…

Linux内核官方文档atomic_ops.txt【摘自Linux 内核文档】

摘自Linux内核文档 Documentation/atomic_ops.txt,不是本人原创 Semantics and Behavior of Atomic and Bitmask Operations David S. Miller This document is intended to serve as a guide to Linux port maintainers on how to implement atomic counter, bitops, and spinlock i…

Method and apparatus for providing total and partial store ordering for a memory in multi-processor system

An improved memory model and implementation is disclosed. The memory model includes a Total Store Ordering (TSO) and Partial Store Ordering (PSO) memory model to provide a partial order for the memory operations which are issued by multiple processor…

Distributed Cache Coherence at Scalable Requestor Filter Pipes that Accumulate Invalidation Acknowledgements from other Requestor Filter Pipes Using Ordering Messages from Central Snoop Tag

A multi-processor, multi-cache system has filter pipes that store entries for request messages sent to a central coherency controller. The central coherency controller orders requests from filter pipes using coherency rules but does not track complet…