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<p><b>Abstract</b>—Although direct-mapped caches suffer from higher miss ratios as compared to set-associative caches, they are attractive for today's high-speed pipelined processors that require very low access times. Victim caching was proposed by Jouppi [<ref rid="bibt06031" type="bib">1</ref>] as an approach to improve the miss rate of direct-mapped caches without affecting their access time. This approach augments the direct-mapped main cache with a small fully-associate cache, called victim cache, that stores cache blocks evicted from the main cache as a result of replacements. We propose and evaluate an improvement of this scheme, called <it>selective victim caching</it>. In this scheme, incoming blocks into the first-level cache are placed selectively in the main cache or a small victim cache by the use of a prediction scheme based on their past history of use. In addition, interchanges of blocks between the main cache and the victim cache are also performed selectively.</p><p>We show that the scheme results in significant improvements in miss rate as well as the average memory access time, for both small and large caches (4 Kbytes-128 Kbytes). For example, simulations with ten instruction traces from the SPEC '92 benchmark suite showed an average improvement of approximately 21percent in miss rate over simple victim caching for a 16-Kbyte cache with a block size of 32 bytes; the number of blocks interchanged between the main and victim caches reduced by approximately 70 percent. Implementation alternatives for the scheme in an on-chip processor cache are also described.</p>
Victim cache, direct-mapped cache, instruction cache, data cache, cache simulation.
Dimitrios Stiliadis, Anujan Varma, "Selective Victim Caching: A Method to Improve the Performance of Direct-Mapped Caches", IEEE Transactions on Computers, vol. 46, no. , pp. 603-610, May 1997, doi:10.1109/12.589235
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