multithreading，multiprocessing

Block multi－threading：context switching意味着从现有的寄存器集切换到另一套

Interleaved multithreading：similar to preemptive multitasking，more modern，需要更大的cache和TLB

Simutaneous multithreading：

instruction level parallelism：measure of  how many of the operations in a computer program can be performed simultaneously

spinlock:repeatedly checking if the lock is available. thread remains active but is not performing a useful task. (busy waiting)

avoid overhead from os process rescheduling or context-switching, efficient if threads are blocked for a short period. wasteful if  held for longer durations.

superscalar cpu

Monitor(synchronization): important
semaphores

test-and-set

processes, kernel threads, user threads, fiber(coroutines)

inter-process communication

interrupt:

hardware interrupt:

non-blocking algorithm:

wait-freedom:

lock-freedom:

software interrupt: