Numbers everyone should know

Jeff Dean, a brilliant engineer at Google, gave a talk a while ago listing the numbers every engineer should know. I copied these from here.

  • 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
  • Send packet CA->Netherlands->CA 150,000,000 ns
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3 Responses to “Numbers everyone should know”

  1. nequitans Says:

    At last a concise place to point to next time someone argues for using a technique purely on its big-O properties while ignoring the system underneath!

  2. Raoul Duke Says:

    some lame quick and dirty excel graph versions, for people who might have a more visual bent to their learning / memory.

    http://grieferz.blogspot.com/2009/03/i-was-seriously-just-today-thinking.html

  3. The Joys of Real Hardware « Handwaving Says:

    [...] Joys of Real Hardware By Pinku Again from a presentation given by Jeff Dean, a brilliant Google engineer. These are the failure rates of [...]

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