The raw increase performance increase that you can get from parallel processing is at the absolute maximum proportionate to the number of processors you can add to your program. Usually it is much less.
A raw performance increase is not the most common good reason for concurrency, for multiple threads or processes in an application though it's a common bad reason. Achieving a decrease in latency is one common good reason to for concurrency on a single machine.
A raw performance increase is not the most common good reason for concurrency, for multiple threads or processes in an application though it's a common bad reason. Achieving a decrease in latency is one common good reason to for concurrency on a single machine.