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.
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.