TinyATD: Compressing Auxiliary Tag Directories using tag hashing and set-sampling

Auxiliary Tag Directories (ATD) are hardware structures widely analyzed in academia to estimate the interference that a task experiences when sharing a cache in a multithreaded system. ATDs are used for execution time inflation calculations, reducing power consumption in multiprocessor systems, improving cache replacement, and improving cache prefetching accuracy. However, the commercial adoption of ATD-based approaches seems to be limited due to the area overheads that they impose. We propose TinyATD, a mechanism that aims to improve state-of-the-art ATD area reduction by combining ATD set sampling and tag hashing area reduction techniques to build smaller and more precise ATDs. TinyATD achieves a 41% area reduction for the same error or a 23% error reduction for the same area over the baseline set-sampling when sampling 32 out of 2048 sets. Furthermore, TinyATD offers the stated reduction over a wide array of commonly used LLC replacement policies.