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Latency numbers every programmer should know
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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 with Zippy 3,000 ns 3 µs | |
Send 2K bytes over 1 Gbps network 20,000 ns 20 µs | |
Read 1 MB sequentially from memory 250,000 ns 250 µs | |
Round trip within same datacenter 500,000 ns 0.5 ms | |
Disk seek 10,000,000 ns 10 ms | |
Read 1 MB sequentially from disk 20,000,000 ns 20 ms | |
Send packet CA->Netherlands->CA 150,000,000 ns 150 ms | |
By Jeff Dean (http://research.google.com/people/jeff/): |
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Lets multiply all these durations by a billion: | |
L1 cache reference 0.5 s One Heart Beat (0.5 s) | |
Branch mispredict 5 s Yawn | |
L2 cache reference 7 s Long Yawn | |
Mutex lock/unlock 25 s ? | |
Main memory reference 100 s Brushing your teeth | |
Compress 1K bytes with Zippy 50 min One episode of a TV show (including ad breaks) | |
Send 2K bytes over 1 Gbps network 5.5 hr Flight duration from Hawaii to Utah | |
Read 1 MB sequentially from memory 2.9 days A long weekend. | |
Round trip within same datacenter 5.8 days A medium vacation | |
Disk seek 16.5 weeks ? | |
Read 1 MB sequentially from disk 7.8 months ? | |
Send packet CA->Netherlands->CA 4.8 years ? |
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