Mechanism for reducing coherence directory controller overhead for near-memory compute elements

Abstract

A parallel processing (PP) level coherence directory, also referred to as a Processing In-Memory Probe Filter (PimPF), is added to a coherence directory controller. When the coherence directory controller receives a broadcast PIM command from a host, or a PIM command that is directed to multiple memory banks in parallel, the PimPF accelerates processing of the PIM command by maintaining a directory for cache coherence that is separate from existing system level directories in the coherence directory controller. The PimPF maintains a directory according to address signatures that define the memory addresses affected by a broadcast PIM command. Two implementations are described: a lightweight implementation that accelerates PIM loads into registers, and a heavyweight implementation that accelerates both PIM loads into registers and PIM stores into memory.