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 ?