| 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 w/ cheap algorithm | 3,000 ns |
| Send 2K bytes over 1 Gbps network | 20,000 ns |
| Read 1 MB sequentially from memory | 250,000 ns |
| Round trip within same datacenter | 500,000 ns |
| Disk seek | 10,000,000 ns |
| Read 1 MB sequentially from disk | 20,000,000 ns |
| Send packet CA->Netherlands->CA | 150,000,000 ns |
For more details: Agner's Software optimization resources.
really like the list. dont know if every programmer needs to knowj all these numbers... just how to derive them is all that is needed. useful though.
ReplyDeletealso: log_2(1000) = ~10, log_2(1000000) = ~20
ReplyDeleteWouldn't disk seek be changed for SSDs?
ReplyDeleteIn the US, a Google search end to end is about 200,000ns. To your desktop.
ReplyDeleteArgh, my apologies. 200,000,000ns for a Google search. 200ms.
ReplyDeleteObviously this is all hardware dependant, but should give a rough idea of the relative costs.
ReplyDeleteConsider a line graph, with latency of access on the Y-axis, and something like "problem size" on the X axis.
ReplyDeleteIf Moore's Law ever had meaning, it tracked how fast the left end of the curve has fallen over time, but I think you'd come to different answers if you looked at different points on the curve.