Cuckoo Directory: A Scalable Directory for Many-Core Systems

Growing core counts have highlighted the need for scalable on-chip coherence mechanisms. The increase in the number of on-chip cores exposes the energy and area costs of scaling the directories. Duplicate-tag based directories require highly associative structures that grow with core count, precluding scalability due to prohibitive power consumption. Sparse directories overcome the power barrier by reducing directory associativity, but require storage area over-provisioning to avoid high invalidation rates. We propose the Cuckoo directory, a power- and area-efficient scalable distributed directory. The cuckoo directory scales to high core counts without the energy costs of wide associative lookup and without gross capacity over-provisioning. Simulation of a 16-core CMP with commercial server and scientific workloads shows that the Cuckoo directory eliminates invalidations while being up to four times more power efficient than the Duplicate-tag directory and 24% more power-efficient and up to seven times more area efficient than the Sparse directory organization. Analytical projections indicate that the Cuckoo directory retains its energy and area benefits with increasing core count, efficiently scaling to at least 1024 cores.


Published in:
Proceedings of the 17th IEEE International Symposium on High Performance Computer Architecture - HPCA 2011
Presented at:
HPCA 2011, San Antonio, Texas, USA, February 12-16, 2011
Year:
2011
Publisher:
IEEE Press
ISBN:
978-1-4244-9432-3
Keywords:
Laboratories:




 Record created 2011-03-08, last modified 2018-11-26

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