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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

Lets multiply all these durations by a billion:

Magnitudes:

Minute:

L1 cache reference 0.5 s One heart beat (0.5 s) Branch mispredict 5 s Yawn L2 cache reference 7 s Long yawn Mutex lock/unlock 25 s Making a coffee 

Hour:

Main memory reference 100 s Brushing your teeth Compress 1K bytes with Zippy 50 min One episode of a TV show (including ad breaks) 

Day:

Send 2K bytes over 1 Gbps network 5.5 hr From lunch to end of work day 

Week

SSD random read 1.7 days A normal weekend Read 1 MB sequentially from memory 2.9 days A long weekend Round trip within same datacenter 5.8 days A medium vacation Read 1 MB sequentially from SSD 11.6 days Waiting for almost 2 weeks for a delivery 

Year

Disk seek 16.5 weeks A semester in university Read 1 MB sequentially from disk 7.8 months Almost producing a new human being The above 2 together 1 year 

Decade

Send packet CA->Netherlands->CA 4.8 years Average time it takes to complete a bachelor's degree