CPHASH: a cache-partitioned hash table

  • Authors:
  • Zviad Metreveli;Nickolai Zeldovich;M. Frans Kaashoek

  • Affiliations:
  • MIT CSAIL, Cambridge, MA, USA;MIT CSAIL, Cambridge, MA, USA;MIT CSAIL, Cambridge, MA, USA

  • Venue:
  • Proceedings of the 17th ACM SIGPLAN symposium on Principles and Practice of Parallel Programming
  • Year:
  • 2012

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Abstract

CPHash is a concurrent hash table for multicore processors. CPHash partitions its table across the caches of cores and uses message passing to transfer lookups/inserts to a partition. CPHash's message passing avoids the need for locks, pipelines batches of asynchronous messages, and packs multiple messages into a single cache line transfer. Experiments on a 80-core machine with 2 hardware threads per core show that CPHash has ~1.6x higher throughput than a hash table implemented using fine-grained locks. An analysis shows that CPHash wins because it experiences fewer cache misses and its cache misses are less expensive, because of less contention for the on-chip interconnect and DRAM. CPServer, a key/value cache server using CPHash, achieves ~5% higher throughput than a key/value cache server that uses a hash table with fine-grained locks, but both achieve better throughput and scalability than memcached. The throughput of CPHash and CPServer also scale near-linearly with the number of cores.