Performance numbers every programmer should know

I just found these “Numbers every programmer should know” in an email I sent to myself a few years ago. I don’t remember the original source of the content, but I know they come from a talk titled “Building Software Systems at Google and Lessons Learned”, by a person named Jeffrey Dean, at Stanford:

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 w/ cheap algorithm     3,000 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 disk    20,000,000 ns
Send packet CA->Netherlands->CA    150,000,000 ns

I wouldn’t worry about committing them to memory any time soon, but it’s nice and interesting to see the relative differences in these numbers/speeds.

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There’s just one person behind this website; if this article was helpful (or interesting), I’d appreciate it if you’d share it. Thanks, Al.

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