Abstract: Simultaneous Multithreading Processors boost performance by executing instructions from different threads simultaneously, which explore both inter-thread and intra-thread parallelism. Sharing critical resources (including rename register file, instruction queue and so on) among different threads may also bring vicious competition,which may resultin starvation,even degrade the performance.This is mainly due to long delays encountered by some thread,and the threads take a lot of key resources for long time,while the demand of the other threads for key resources cannot be met.This may reduce the utilization of resources.There are three methods to reduce the negative impact of competition:thread scheduling decides which threads to fetch instructions from in the fetch stage;instruction scheduling determine which instructions to enter the key resource in the dispatch stage;Partitions of the key resources allocate the key resources among threads.These scheduling strategies were reviewed in the paper.

Key words: SMT, Thread scheduling,Instruction scheduling,Resources partitions