Multithreaded Processors
Multithreaded Processors
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DOI：
10.1093/comjnl/45.3.320
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发表时间：
2002
期刊：
影响因子：
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通讯作者：
T. Ungerer;B. Robic;J. Silc
中科院分区：
文献类型：
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作者：
T. Ungerer;B. Robic;J. Silc
在常规指令流中发现的并行级并行性是有限的。研究表明，即使对于今天的超标量微处理器，处理器的利用率也是有限的。一种解决方案是额外利用更粗粒度的并行性。主要的方法是（单）芯片多处理器和多线程处理器，优化多线程工作负载的吞吐量，而不是单线程性能。片上多处理器在一个芯片上集成了两个或多个完整的处理器。处理器的每个单元都是独立于芯片上的副本复制和使用的。相比之下，多线程处理器能够在处理器流水线内并行地执行两个或更多个控制线程。未使用的指令槽，这是由当代微处理器的单线程程序的流水线执行产生的，由多线程处理器内的其他线程的指令填充。执行单元在寄存器组中的线程之间多路复用。超标量处理器由于缺少并行级而导致的利用率不足可以通过同时多线程来克服，其中处理器可以在每个周期从多个线程发出多条指令。同时多线程处理器联合收割机将多线程技术与宽发布超标量处理器相结合，使得通过潜在地同时从不同线程发布指令来利用全部发布带宽。这篇综述论文解释和分类了研究和商业微处理器中的各种多线程技术，并将多线程处理器与片上多处理器进行了比较。
The instruction-level parallelism found in a conventional instruction stream is limited. Studies have shown the limits of processor utilization even for today’s superscalar microprocessors. One solution is the additional utilization of more coarse-grained parallelism. The main approaches are the (single) chip multiprocessor and the multithreaded processor which optimize the throughput of multiprogramming workloads rather than single-thread performance. The chip multiprocessor integrates two or more complete processors on a single chip. Every unit of a processor is duplicated and used independently of its copies on the chip. In contrast, the multithreaded processor is able to pursue two or more threads of control in parallel within the processor pipeline. Unused instruction slots, which arise from pipelined execution of single-threaded programs by a contemporary microprocessor, are filled by instructions of other threads within a multithreaded processor. The execution units are multiplexed between the threads in the register sets. Underutilization of a superscalar processor due to missing instruction-level parallelism can be overcome by simultaneous multithreading, where a processor can issue multiple instructions from multiple threads each cycle. Simultaneous multithreaded processors combine the multithreading technique with a wideissue superscalar processor such that the full issue bandwidth is utilized by potentially issuing instructions from different threads simultaneously. This survey paper explains and classifies the various multithreading techniques in research and in commercial microprocessors and compares multithreaded processors with chip multiprocessors.