U-cache: a cost-effective solution to synonym problem

Jesung Kim Jesung Kim,Deog-Kyoon Jeong Deog-Kyoon Jeong,Chong Sang Kim Chong Sang Kim,Sanghoon Jeon Sanghoon Jeon,Byoungchu Ahn Byoungchu Ahn,Sang Lyul Min Sang Lyul Min

doi:10.1109/hpca.1995.386538

Abstract

This paper proposes a cost-effective solution to the synonym problem. In this proposed solution, a minimal hardware addition guarantees the correctness whereas the software counterpart helps improve the performance. The key to this proposed solution is an addition of a small physically-indexed cache called U-cache. The U-cache maintains the reverse translation information of the cache blocks that belong to un-aligned virtual pages only, where aligned means that the lower bits of the virtual page number match those of the corresponding physical page number. A U-cache, even with only one entry, ensures correct handling of synonyms. A simple software optimization in the form of page alignment, helps improve the performance. Performance evaluation based on ATUM traces shows that a U-cache, with only a few entries, performs almost as well as (in some cases outperforms) a fully-configured hardware-based solution when more than 95% of the pages are aligned. >

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