Content-directed prefetch circuit with quality filtering

Abstract

In a content-directed prefetcher, a pointer detection circuit identifies a given memory pointer candidate within a data cache line fill from a lower level cache (LLC), where the LLC is at a lower level of a memory hierarchy relative to the data cache. A pointer filter circuit initiates a prefetch request to the LLC candidate dependent on determining that a given counter in a quality factor (QF) table satisfies QF counter threshold value. The QF table is indexed dependent upon a program counter address and relative cache line offset of the candidate. Upon initiation of the prefetch request, the given counter is updated to reflect a prefetch cost. In response to determining that a subsequent data cache line fill arriving from the LLC corresponds to the prefetch request for the given memory pointer candidate, a particular counter of the QF table may be updated to reflect a successful prefetch credit.