If a system performance is profiled as being dominated by 80% A , 19% B and 1 % C. I'd focus on working on A first to get maximum gains. Amdahl's law gives you

If a system performance is profiled as being dominated by 80% A , 19% B and 1 % C. I'd focus on working on A first to get maximum gains. Amdahl's law gives you the backing as to why you should do this. As a real world example, if an operation involves a network call and you see the RTT dominating the time. You may want to think of ways to avoid the call (caching etc..) if possible to get really good gains.