In-Network Snoop Ordering (INSO): Snoopy coherence on unordered interconnects

Realizing scalable cache coherence in the many-core era comes with a whole new set of constraints and opportunities. It is widely believed that multi-hop, unordered on-chip networks would be needed in many-core chip multiprocessors (CMPs) to provide scalable on-chip communication. However, providing ordering among coherence transactions on unordered interconnects is a challenge. Traditional approaches for tackling coherence either have to use ordered interconnects (snoopbased protocols) which lead to scalability problems, or rely on an ordering point (directory-based protocols) which adds indirection latency. In this paper, we propose In-Network Snoop Ordering (INSO), in which coherence requests from a snoop-based protocol are inserted into the interconnect fabric and the network orders the requests in a distributed manner, creating a global ordering among requests. Essentially, when coherence requests enter the network, they grab snoop-orders at the injection router before being broa...

• Type: Conference
• Year: 2009
• Where: HPCA
• Authors: Niket Agarwal, Li-Shiuan Peh, Niraj K. Jha
• Keywords: Cache Coherence Protocol, Coherence Requests, Computer Architecture, HPCA 2009, Token Coherence Protocol