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Abstract : |
When a computer system supports both paged virtual memory and large real-indexed caches, cache performance depends in part on the main memory page placement. To date, most operating systems place pages by selecting an arbitrary page frame from a pool of page frames that have been made available by the page replacement algorithm. We give a simple model that shows that this naive (arbitrary) page placement leads to up to 30 % unnecessary cache conflicts. We develop several page placement algorithms, called careful-mapping algorithms, that try to select a page frame (from the pool of available page frames) that is likely to reduce cache contention. Using trace-driven simulation, we find that careful-mapping results in 10-20 % fewer (dynamic) cache misses than naive mapping (for a direct-mapped real-indexed multi-megabyte cache). Thus, our results suggest that careful-mapping by the operating system can get about half the cache miss reduction that a cache size (or associativity) doubling can. 1., |
