Latency Numbers
2 minutes read •
Latency Numbers
Years ago I read an article about computer performance. To illustrate the computing power of a CPU, in contrast to the data-providing parts of a computer, it symbolized a cycle-time of the processor with 1 second. From the view of a CPU, how long to wait for data in relation.
While searching a little bit, I found several quite old sources for the numbers and realized they haven’t changed much over the years.
| periphery | 2012 | 2 GHz => 1 Hz | 2025 | 4 GHz => 1 Hz |
|---|---|---|---|---|
| processor cycle | 0.5 | 1.0 sec. | 0.25 | 1,0 sec. |
| execute typical instruction | 0.75 | 1.5 sec. | 0.4 | 1.6 sec. |
| L1 cache reference | 0.5 | 1.0 sec. | 0.7 | 2.8 sec. |
| L2 cache reference | 7 | 14.0 sec. | 2.5 | 10.0 sec. |
| Branch mispredict | 5 | 10.0 sec. | 8 | 32.0 sec. |
| Mutex lock/unlock | 25 | 50.0 sec. | 25 | 100.0 sec. |
| Main memory reference | 100 | 3.3 min. | 80 | 5.3 min. |
| Compress 1K bytes with Zippy | 3,000 | 100.0 min. | 2,000 | 133.3 min. |
| Send 2K bytes over 1 Gbps network | 16,000 | 8.9 h | 16,000 | 17.8 h |
| Read 1 MB sequentially from memory | 250,000 | 5.8 days | 20,000 | 0.9 days |
| Read 1 MB sequentially from SSD | 1,000,000 | 23.1 days | 200,000 | 9.3 days |
| Round trip within same datacenter | 500,000 | 11.6 days | 80,000 | 3.7 days |
| Disk seek HDD | 10,000,000 | 7.7 month | 4,000,000 | 6.2 month |
| Read 1 MB sequentially from HDD | 20,000,000 | 15.4 month | 10,000,000 | 15.4 month |
| Send packet CA->NL->CA | 150,000,000 | 115.7 month | 145,000,000 | 223.8 month |
Source:
https://gist.github.com/hellerbarde/2843375
https://surana.wordpress.com/2009/01/01/numbers-everyone-should-know/