一些我们需要知道的时间指标

• 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

Reference: http://surana.wordpress.com/2009/01/01/numbers-everyone-should-know/