有两类程序员几乎不出 多线程bug：一类是啥也不懂，只要涉及到多 线程 就直接上锁；另一类熟读内存模型、体系结构、缓存一致性协议、内存屏障、竞态条件、指令重排……然后决定只要涉及到 多线程 就直接上锁。
“Concurrency is about dealing with lots of things at once.
Parallelism is about doing lots of things at once” – Rob Pike
- To overlap disk O requests
- To reduce latency by prefetching results to expected queries
- To take advantage of multiple processors.
Concurrency is having two tasks run in parallel on separate threads. However, asynchronous run in parallel but on the same thread.