Latency Numbers Every Programmer Should Know

latency.txt

Latency Comparison Numbers
--------------------------
memory    L1 cache reference                           0.5 ns
memory    Branch mispredict                            5   ns
memory    L2 cache reference                           7   ns                      14x L1 cache
memory    Mutex lock/unlock                           25   ns
memory    Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
          Compress 1K bytes with Zippy             3,000   ns        3 us
network   Send 1K bytes over 1 Gbps network       10,000   ns       10 us
disk      Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD
memory    Read 1 MB sequentially from memory     250,000   ns      250 us
network   Round trip within same datacenter      500,000   ns      500 us
disk      Read 1 MB sequentially from SSD*     1,000,000   ns    1,000 us    1 ms  ~1GB/sec SSD, 4X memory
disk      Disk seek                           10,000,000   ns   10,000 us   10 ms  20x datacenter roundtrip
disk      Read 1 MB sequentially from disk    20,000,000   ns   20,000 us   20 ms  80x memory, 20X SSD
network   Send packet CA->Netherlands->CA    150,000,000   ns  150,000 us  150 ms

Reading/writing to disk;       100x slower than in-memory
Network communication;   1,000,000x slower than in-memory

Notes
-----
1 ns = 10^-9 seconds
1 us = 10^-6 seconds = 1,000 ns
1 ms = 10^-3 seconds = 1,000 us = 1,000,000 ns

Credit
------
By Jeff Dean:               http://research.google.com/people/jeff/
Originally by Peter Norvig: http://norvig.com/21-days.html#answers

Contributions
-------------
Some updates from:       https://gist.github.com/2843375
'Humanized' comparison:  https://gist.github.com/2843375
Visual comparison chart: http://i.imgur.com/k0t1e.png
Animated presentation:   http://prezi.com/pdkvgys-r0y6/latency-numbers-for-programmers-web-development/latency.txt