Global management of cache hierarchies

Abstract

Cache memories currently treat all blocks as if they were equally important. This assumption of equally important blocks is not always valid. For instance, not all blocks deserve to be in L1 cache. We therefore propose globalized block placement. We present a global placement algorithm for managing blocks in a cache hierarchy by deciding where in the hierarchy an incoming block should be placed. Our technique makes decisions by adapting to access patterns of different blocks. The contributions of this paper are fourfold. First, we motivate our solution by demonstrating the importance of a globalized placement scheme. Second, we present a method to categorize cache block behavior into one of four categories. Third, we present one potential design exploiting this categorization. Finally, we demonstrate the performance of our design. The proposed scheme enhances overall system performance (IPC) by an average of 12% over a traditional LRU scheme while reducing traffic between L1 cache and L2 cache by an average of 20%, using SPEC CPU benchmark suite. All of this is achieved with a table as small as 3 KB.