In chip multiprocessors (CMPs), limiting the number of off-chip cache misses is crucial for good performance. Many multithreaded programs provide opportunities for constructive cache sharing, in which concurrently sch...
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ISBN:
(纸本)9781595934529
In chip multiprocessors (CMPs), limiting the number of off-chip cache misses is crucial for good performance. Many multithreaded programs provide opportunities for constructive cache sharing, in which concurrently scheduled threads share a largely overlapping working set. In this brief announcement, we highlight our ongoing study [4] comparing the performance of two schedulers designed for fine-grained multithreaded programs: Parallel Depth First (PDF) [2], which is designed for constructive sharing, and Work Stealing (WS) [3], which takes a more traditional *** of schedulers. In PDF, processing cores are allocated ready-to-execute program tasks such that higher scheduling priority is given to those tasks the sequential program would have executed earlier. As a result, PDF tends to co-schedule threads in a way that tracks the sequential execution. Hence, the aggregate working set is (provably) not much larger than the single thread working set [1]. In WS, each processing core maintains a local work queue of readyto-execute threads. Whenever its local queue is empty, the core steals a thread from the bottom of the first non-empty queue it finds. WS is an attractive scheduling policy because when there is plenty of parallelism, stealing is quite rare. However, WS is not designed for constructive cache sharing, because the cores tend to have disjoint working *** configurations studied. We evaluated the performance of PDF and WS across a range of simulated CMP configurations. We focused on designs that have fixed-size private L1 caches and a shared L2 cache on chip. For a fixed die size (240 mm2), we varied the number of cores from 1 to 32. For a given number of cores, we used a (default) configuration based on current CMPs and realistic projections of future CMPs, as process technologies decrease from 90nm to *** of findings. We studied a variety of benchmark programs to show the following *** several application classes, PDF enable
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