Latency numbers every programmer should know
L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns
Compress 1K bytes with Zippy ............. 3,000 ns = 3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns = 20 µs
SSD random read ........................ 150,000 ns = 150 µs
Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs
Round trip within same datacenter ...... 500,000 ns = 0.5 ms
Read 1 MB sequentially from SSD* ..... 1,000,000 ns = 1 ms
Disk seek ........................... 10,000,000 ns = 10 ms
Read 1 MB sequentially from disk .... 20,000,000 ns = 20 ms
Send packet CA->Netherlands->CA .... 150,000,000 ns = 150 ms
Assuming ~1GB/sec SSD
Visual chart provided by ayshen
Data by Jeff Dean
Originally by Peter Norvig
25s is making one coffee. 7.8 months is a tad faster than producing a new human being. One disk-seek (16 weeks) and then reading 1MiB (7.8 months) is one year.
thx, will incorporate those!
16.5 weeks ~= four months ~= full semester at university ~= summer break ?
Such an accurate portrayal. "yawwwn aw damn it fell through to the else again."
4.8 years is very roughly two round trips to Mars. Or a one-way trip to Europa.
neat, thanks!
4.8 years is about how long a bachelor's degree takes on average (4.7 years in 2008 according to this page).
Should add date of creation to text itself (as of ...)
If enough people start reading this, the last one will have to wait several years
Here's a tool to visualize these numbers over time: http://www.eecs.berkeley.edu/~rcs/research/interactive_latency.html
Great interactive chart! Suggest to add CPU cycles for a simple single instructions such as ADD, MOV, MULT (e.g. "multiplying two 16bit integers".
I'd like to see a duration for function-call overhead. Late 80s when I was in school, it was several micro-seconds, enough that people had concerns about having unnecessary function calls. I'm sure that doesn't apply any more, but I don't have real numbers.