Latency Numbers Every Programmer Should Know

latency.txt

Latency Comparison Numbers (~2012)
----------------------------------
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        3 us
Send 1K bytes over 1 Gbps network         10,000   ns       10 us
Read 4K randomly from SSD*               150,000   ns      150 us             ~1GB/sec SSD
Read 1 MB sequentially from memory       250,000   ns      250 us
Round trip within same datacenter        500,000   ns      500 us
Read 1 MB sequentially from SSD*       1,000,000   ns    1,000 us       1 ms  ~1GB/sec SSD, 4X memory
Disk seek                             10,000,000   ns   10,000 us      10 ms  20x datacenter roundtrip
Read 1 MB sequentially from disk      20,000,000   ns   20,000 us      20 ms  80x memory, 20X SSD
Send packet CA->Netherlands->CA      150,000,000   ns  150,000 us     150 ms
Read 4K randomly from RPI SD card   9999,999,999   ns   "lots" us  "tons" ms  Takes twice as long as the age of the universe

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
Age of the universe = about 14 billion years

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

Contributions
-------------
'Humanized' comparison:  https://gist.github.com/hellerbarde/2843375
Visual comparison chart: http://i.imgur.com/k0t1e.png
Lynne: accurate measurements of a Raspberry Pi 3 SD card access