Latency Numbers Every Programmer Should Know - MarkDown Fork

latency_numbers.md

Latency Comparison Numbers

Note: "Forked" from Latency Numbers Every Programmer Should Know

Event	Nanoseconds	Microseconds	Milliseconds	Comparison
L1 cache reference	0.5	-	-	-
Branch mispredict	5.0	-	-	-
L2 cache reference	7.0	-	-	14x L1 cache
Mutex lock/unlock	25.0	-	-	-
Main memory reference	100.0	-	-	20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy	3,000.0	3	-	-
Send 1K bytes over 1 Gbps network	10,000.0	10	-	-
Read 4K randomly from SSD	150,000.0	150	-	~1GB/sec SSD
Read 1 MB sequentially from memory	250,000.0	250	-	-
Round trip within same datacenter	500,000.0	500	-	-
Read 1 MB sequentially from SSD	1,000,000.0	1,000	1	~1GB/sec SSD, 4X memory
Disk seek	10,000,000.0	10,000	10	20x datacenter roundtrip
Read 1 MB sequentially from disk	20,000,000.0	20,000	20	80x memory, 20X SSD
Send packet CA → Netherlands → CA	150,000,000.0	150,000	150	-

Unit Reference

• 1 ns = 10^-9 seconds
• 1 µs = 10^-6 seconds = 1,000 ns
• 1 ms = 10^-3 seconds = 1,000 µs = 1,000,000 ns

Credit/Notes

• By Jeff Dean
• Originally by Peter Norvig
• Presentation - Latency Numbers for Programmers

Visual Comparison Charts