An Algorithm to Resolve Multiple-Copy Cache Conflicts in Multi-Node Systems with Ring Topology
Original Publication Date: 2002-Sep-01
Included in the Prior Art Database: 2003-Jun-21
Background of the Invention Field of the Invention Disclosed is an algorithm based methodology to resolve multiple-copy cache conflicts in multi-node computer systems with ring topology. A multi-node computer system is a cluster of multi-processor (MP) computer nodes with a common view to storage hierarchy. The processors at each node share one common level 2 cache (L2) and each node owns and manages a local portion of the common memory [Fig 1]. A common view to all the caches and memories distributed across the various nodes is provided by the cache coherence protocol. The invention relates to clusters where the buses connecting the individual MP nodes form a ring. As shown in [Fig 2], the ring connection is assumed to consist of two sets of uni-directional ring buses in opposite direction each set comprising address/command and data buses. Address/command and data buses may be separate or combined to one bus. Such bi-directional ring structures are usually preferred over one-directional ring structures because they have far better cache-to-cache and memory-to-cache data transfer latencies between nodes. To exploit the bi-directional structure, ring requests are launched in both directions.