Numbers that every computer engineer should know.

• 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
• Greatest latency that appears real-time for interactive UI: 100,000,000 ns
• Greatest latency that appears real-time for query based UI: 250,000,000 ns
• Send packet CA->Netherlands->CA: 150,000,000 ns