Can anyone explain what is std::memory_order in plain English,

我找到的各种记忆顺序最好的“普通英语”解释是Bartoz Milewski的关于松弛原子的文章：http://bartoszmilewski.com/2008/12/01/c-atomics-and-memory-ordering/

后续岗位：http://bartoszmilewski.com/2008/12/23/the-inscrutable-c-memory-model/

但请注意，尽管这些文章是一个很好的介绍，他们在C 11标准之前，并不会告诉你一切你需要知道的安全使用它们。

and how to use them with std::atomic<>?

我最好的建议是：不要。轻松的原子是(可能)C中最棘手和最危险的东西11.坚持std :: atomic< T>与默认内存排序(顺序一致性)，直到你真的，真的确保你有一个性能问题，可以通过使用宽松的内存排序解决。

在上面链接的第二篇文章中，Bartoz Milewski得出以下结论：

I had no idea what I was getting myself into when attempting to reason
about C++ weak atomics. The theory behind them is so complex that it’s
borderline unusable. It took three people (Anthony, Hans, and me) and
a modification to the Standard to complete the proof of a relatively
simple algorithm. Imagine doing the same for a lock-free queue based
on weak atomics!