Latency Numbers Every Programmer Should Know.md

Latency Comparison Numbers (~2012)

Name
L1 cache reference	0.5	ns
Branch mispredict	5	ns
L2 cachereference	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 Gb ps 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	20,000,000	ns	20,000	us	20	ms	80x memory, 20X SSD
Send pack et CA->Netherlands->CA	150,000,000	ns	150,000	us	150	ms

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

Original: https://gist.github.com/jboner/2841832

‘Humanized’ comparison: https://gist.github.com/hellerbarde/2843375

Visual comparison chart: http://i.imgur.com/k0t1e.png

Much easier to view. You could also embed the visual chart