RegionScout: Exploiting Coarse Grain Sharing in Snoop-Based Coherence

It has been shown that many requests miss in all remote nodes in shared memory multiprocessors. We are motivated by the observation that this behavior extends to much coarser grain areas of memory. We define a region to be a continuous, aligned memory area whose size is a power of two and observe that many requests find that no other node caches a block in the same region even for regions as large as 16K bytes. We propose RegionScout, a family of simple filter mechanisms that dynamically detect most non-shared regions. A node with a RegionScout filter can determine in advance that a request will miss in all remote nodes. RegionScout filters are implemented as a layered extension over existing snoop-based coherence systems. They require no changes to existing coherence protocols or caches and impose no constraints on what can be cached simultaneously. Their operation is completely transparent to software and the operating system. RegionScout filters require little additional storage an...

• Type: Conference
• Year: 2005
• Where: ISCA
• Authors: Andreas Moshovos
• Keywords: Hardware, ISCA 2005, Non-shared Regions, Regionscout Filters, Remote Nodes