Out-of-order execution may not be cost-effective on processors featuring simultaneous multithreading
Out-of-order execution may not be cost-effective on processors featuring simultaneous multithreading
复制标题
在具有同步多线程功能的处理器上，乱序执行可能不具有成本效益
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
André Seznec
中科院分区：
文献类型：
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作者：
S. Hily;André Seznec
为了在单个进程上实现高性能，超标量处理器现在依赖于非常复杂的无序执行。为了进一步改进，需要使用越来越多的投机性执行(例如，值预测)。另一方面，大多数操作系统现在提供分时多进程环境。目前，大多数时间都花在单个线程上，但这种情况应该会改变，因为计算机将执行越来越多的独立任务。此外，桌面应用程序往往是多线程的。因此，许多用户应该更关心工作负载的性能吞吐量，而不是单个进程上处理器的性能。同步多线程(SMT)是从超标量流水线传输高吞吐量的一种很有前途的方法。在本文中，我们证明了当在SMT处理器上执行4个线程时，无序执行比按序执行带来的性能优势要小得多。然后，对于单个应用程序上的性能吞吐量比最终性能更重要的应用程序领域，SMT与有序执行相结合可能是比最终激进的无序超标量处理器或无序执行SMT更具成本效益的替代方案。
To achieve high performance on a single process, superscalar processors now rely on very complex out-of-order execution. Using more and more speculative execution (e.g. value prediction) will be needed for further improvements. On the other hand, most operating systems now offer time-shared multiprocess environments. For the moment most of the time is spent in a single thread, but this should change, as the computer will perform more and more independent tasks. Moreover, desktop applications tend to be multithreaded. A lot of users should then be more concerned with the performance throughput on the workload than with the performance of the processor on a single process. Simultaneous multithreading (SMT) is a promising approach to deliver high throughput from superscalar pipelines. In this paper, we show that when executing 4 threads on an SMT processor, out-of-order execution induces small performance benefits over in-order execution. Then, for application domains where performance throughput is more important than ultimate performance on a single application, SMT combined with in-order execution may be a more cost-effective alternative than ultimate aggressive out-of-order superscalar processors or out-of-order execution SMT.