Friday, 10 April 2015

Numbers that every computer engineer should know.



  • L1 cache reference: 0.5 ns
  • Branch mispredict: 5 ns
  • L2 cache reference: 7 ns
  • Mutex lock/unlock: 100 ns
  • Main memory reference: 100 ns
  • Compress 1K bytes with Zippy: 10,000 ns
  • Send 2K bytes over 1 Gbps network: 20,000 ns
  • Read 1 MB sequentially from memory: 250,000 ns
  • Round trip within same datacenter: 500,000 ns
  • Disk seek: 10,000,000 ns
  • Read 1 MB sequentially from network: 10,000,000 ns
  • Read 1 MB sequentially from disk: 30,000,000 ns
  • Greatest latency that appears real-time for interactive UI: 100,000,000 ns
  • Greatest latency that appears real-time for query based UI: 250,000,000 ns
  • Send packet CA->Netherlands->CA: 150,000,000 ns

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