Latency Comparison Numbers

Автор: Silver

Просмотров: 105

Latency Comparison Numbers
--------------------------
L1 cache reference                                  0.5 ns
Branch mispredict                                   5   ns
L2 cache reference                                  7   ns             14x L1 cache
Mutex lock/unlock                                  25   ns
Main memory reference                             100   ns             20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy                    3,000   ns
Send 1K bytes over 1 Gbps network              10,000   ns    0.01 ms
Read 4K randomly from SSD*                    150,000   ns    0.15 ms
Read 1 MB sequentially from memory            250,000   ns    0.25 ms
Round trip within same datacenter             500,000   ns    0.5  ms
Read 1 MB sequentially from SSD*            1,000,000   ns    1    ms  4X memory
Disk seek                                  10,000,000   ns   10    ms  20x datacenter roundtrip
Read 1 MB sequentially from disk           20,000,000   ns   20    ms  80x memory, 20X SSD
Send packet CA->Netherlands->CA     150,000,000   ns  150    ms

Notes
-----
1 ns = 10-9 seconds
1 ms = 10-3 seconds
* Assuming ~1GB/sec SSD

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
Great 'humanized' comparison version:   https://gist.github.com/2843375
Visual comparison chart:                http://i.imgur.com/k0t1e.png
Nice animated presentation of the data: http://prezi.com/pdkvgys-r0y6/latency-numbers-for-programmers-web-development/