Amdahl's Law
Speedup = 1 / (s + p/N), where s is the serial fraction.
Origin
Gene Amdahl proposed it at the 1967 AFIPS Spring Joint Computer Conference while pushing back on overhyped parallel-computing claims.
Where it shows up in production
- Database scale-out A 1% serial fraction caps speedup at 100×, regardless of how many shards you add.
- Web request latency The slow database call gates everything around it; parallelising other work has rapidly diminishing returns.
On Semicolony
Sources & further reading
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