Latency Numbers Every Programmer Should Know
31 Dec 2015Latency Comparison Numbers
| Operation | Time in ns | Time in ms | Comment |
|---|---|---|---|
| L1 cache reference | 0.5 | ||
| Branch mispredict | 5 | ||
| L2 cache reference | 7 | 14x L1 cache | |
| Mutex lock/unlock | 25 | ||
| Main memory reference | 100 | 20x L2 cache, 200x | |
| Compress 1K bytes with Zip | 3,000 | ||
| Send 1K bytes over 1 Gbps network | 10,000 | 0.01 | |
| Read 4K randomly from SSD | 150,000 | 0.15 | |
| Read 1 MB sequentially from memory | 250,000 | 0.25 | |
| Round trip within same datacenter | 500,000 | 0.5 | |
| Read 1 MB sequentially from SSD | 1,000,000 | 1 | 4X memory |
| Disk seek | 10,000,000 | 10 | 20x datacenter roundtrip |
| Read 1 MB sequentially from disk | 20,000,000 | 20 | 80x memory, 20X SSD |
| Send packet CA->Netherlands->CA | 150,000,000 | 150 |
Notes
1 ns = 10^-9 seconds
1 ms = 10^-3 seconds
Assuming ~1GB/sec SSD
Credit
By Jeff Dean: http://research.google.com/people/jeff/
Originally by Peter Norvig: http://norvig.com/21-days.html#answers