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Latency

Latency Numbers Every Data Scientist Should Know

In the 2000s, Jeff Dean, a Google Senior Fellow in their Research Group, presented a list of latency numbers that every programmer should know. These numbers describe how long it takes to perform certain actions within distributed programs. Since then, it has been updated and expanded upon.

Below is yet another update on these numbers with data taken from Colin Scott, a Berkeley researcher. An interactive version of this repository can be found here.

Action Latency (ns)1 Latency (μ)2 Latency (ms)3
L1 cache reference 1 ns
Branch mispredict 3 ns
L2 cache reference 4 ns
Mutex lock/unlock 17 ns
Main memory reference 100 ns
Compress 1KB with Zippy 2,000 ns 2 μs
Send 1KB over 1 Gbps network 10,000 ns 10 μs
SSD random read 16,000 ns 16 μs
Read 1 MB sequentially from SSD 49,000 ns 49 μs
Read 1 MB sequentially from memory 250,000 ns 250 μs
Round trip within same datacenter 500,000 ns 500 μs
Read 1 MB sequentially from disk 825,000 ns 825 μs
Disk seek 2,000,000 ns 2,000 μs 2 ms
Send packet CA->Netherlands->CA 150,000,000 ns 150,000 μs 150 ms

Notes

  1. 1 ns = 10-9 seconds ↩

  2. 1 μs = 10-6 seconds = 1,000 ns ↩

  3. 1 ms = 10-3 seconds = 1,000 μs = 1,000,000 ns ↩

Last update: March 12, 2023