Latency Numbers Programmers Should Know

Things on this page are fragmentary and immature notes/thoughts of the author. Please read with your own judgement!

Latency	Operations
<=1ns	accessing CPU registers CPU clock cycle L1 cache
1-10ns	L2 cache branch mispredict
10-100ns	L3 cache mutex lock/unlock main memory referencing
100-1000ns	trapping of system call md5 hash of an u64
1-10us	process context switching compress 1k with zippy memory copy of 64k
10-100us	network proxy / http request read 1M from memory SSD latency (read a 8k page)
100-1000us	SSD write latency / write a page intra-zone networking round trip memcache/redis get operation (measured by client including network round trip)
1-10ms	inter-zone networking latency hard drive latency
10-100ms	network round trip between US coasts network round trip between US east coast and Europe read 1G from memory
100-1000ms	bcypt a password TLS handshae (250-500ms) network round trip from US west coast to Singapore read 1G from SSD
>=1s	transfer 1G over a network in the same region

References¶