MAPS: Understanding Metadata Access Patterns in Secure Memory

Secure memory increases both the latency and energy required for memory accesses. To reduce these overheads, computer architects have sought to cache metadata on the processor chip, but placing metadata in a simple cache has not been as effective as expected. With a detailed analysis of metadata access patterns, we clarify myths in metadata caching and provide insight into more efficient caching strategies. We provide three observations that can help architects design future metadata caches. First, caching all metadata types improves efficiency. Second, the size of the metadata cache should match the reuse distance of the metadata. Third, when designing a better eviction policy, the traditional Belady's MIN algorithm cannot be used as the optimal replacement policy.