每一位计算机工程师都应该知道的数字(by Jeff Dean)

L1 cache reference: 0.5 ns
Branch mispredict: 5 ns
L2 cache reference: 7 ns
Mutex lock/unlock: 100 ns
Main memory reference: 100 ns
Compress 1K bytes with Zippy: 10,000 ns
Send 2K bytes over 1 Gbps network: 20,000 ns
Read 1 MB sequentially from memory: 250,000 ns
Round trip within same datacenter: 500,000 ns
Disk seek: 10,000,000 ns
Read 1 MB sequentially from network: 10,000,000 ns
Read 1 MB sequentially from disk: 30,000,000 ns
Send packet CA->Netherlands->CA: 150,000,000 ns

(note that 1 ns = 1 * 10^-9 s)

图相版本: http://www.eecs.berkeley.edu/~rcs/research/interactive_latency.html