Method and apparatus for allocating data and instructions within a shared cache

Abstract

A method and apparatus are provided for managing cache allocation for a plurality of data types in a unified cache having dynamically allocable lines for first type data and for second type data. Cache allocation is managed by counting misses to first type data and misses to second type data in the unified cache, and by determining when a difference between a number of first type data misses and a number of second type data misses crosses a preselected threshold. A replacement algorithm of the unified cache then is adjusted in response to the detected crossing of the preselected threshold, the adjusting step including increasing a replacement priority of the first type data lines in the cache. The replacement algorithm preferably is an LRU algorithm wherein the adjusting step includes incrementing an age indication of the first type data lines. Hardware for implementing the inventive cache allocation management method comprises a miss counter configured to increment its count in response to a miss to first type data signal on a first counter input and to output a first logic state on a first counter output when the counter's count exceeds a first predetermined count. A priority adjustment circuit coupled to the first counter output increases the replacement priority of the first type data relative to the replacement priority of the second type data in response to the first logic state output by the miss counter.