Latency Numbers Every Programmer Should Know

latency.txt

Latency Comparison Numbers Simplified (~2012)
----------------------------------   log2 log10
L1 cache reference                     0    0    ~ 1 ns
Branch mispredict                      3    1
L2 cache reference                     4    1
Mutex lock/unlock                      6    2
Main memory reference                  8    2
Compress 1K bytes with Zippy          13    4
Send 1K bytes over 1 Gbps network     14    4
Read 4K randomly from SSD*            18    5
Read 1 MB sequentially from memory    19    6
Round trip within same datacenter     20    6
Read 1 MB sequentially from SSD*      21    6
Disk seek                             24    7
Read 1 MB sequentially from disk      25    8
Send packet CA->Netherlands->CA       28    9

Notes
-----
The log2 and log10 columns have logarithm computations (rounded to an integer power)
relative to the first item on the list (L1 cache reference). I find that the exact
numbers are not terribly important. It is much simpler to reason about relative
dimensions in this format---simply take two elements in a column and subtract
them. For example, using the log10 column, "Read 1 MB sequentially from memory"
is about 1000000 slower than "L1 cache reference" and 10000 slower than
"Main memory reference". For very rough back-of-the-envelope computations, I often
use 2^10 ~ 10^3 and 2^3 ~ 10^1, e.g., "Send 1K bytes over 1 Gbps network" is about
16000 slower than "L1 cache reference". The logarithms were computed from the
numbers found in https://gist.github.com/jboner/2841832.

Not sure about log2 here. Rounded up at https://gist.github.com/artkpv/dce2870a8241ff2c0164337422566fc5