Numbers everyone should know
Jeff Dean, a brilliant engineer at Google, gave a talk a while ago listing the numbers every engineer should know. I copied these from here.
- L1 cache reference 0.5 ns
- Branch mispredict 5 ns
- L2 cache reference 7 ns
- Mutex lock/unlock 100 ns
- Main memory reference 100 ns
- Compress 1K bytes with Zippy 10,000 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 network 10,000,000 ns
- Read 1 MB sequentially from disk 30,000,000 ns
- Send packet CA->Netherlands->CA 150,000,000 ns
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At last a concise place to point to next time someone argues for using a technique purely on its big-O properties while ignoring the system underneath!
some lame quick and dirty excel graph versions, for people who might have a more visual bent to their learning / memory.
http://grieferz.blogspot.com/2009/03/i-was-seriously-just-today-thinking.html