1.9.2 Concurrency and Parallelism

1. Thread-Level Concurrency

• With threads, we can even have multiple control flows executing within a single process.
• most actual computing was done by a single processor, even if that processor had to switch among multiple tasks. This configuration is known as a uniprocessor system.

• Hyperthreading, sometimes called simultaneous multi-threading, is a technique that allows a single CPU to execute multiple flows of control.
• if one thread must wait for some data to be loaded into a cache, the CPU can proceed with the execution of a different thread.
• The use of multiprocessing can improve system performance in two ways. First, it reduces the need to simulate concurrency when performing multiple tasks.
• it can run a single application program faster, but only if that program is expressed in terms of multiple threads that can effectively execute in parallel.