1. A method comprising: identifying, by a look-ahead processor, instructions that are at least likely to be executed by a main processor including plural power states including plural non-idle performance states with respective different clock frequencies; determining, by said lookahead processor and based on the identified instructions, a suitable non-idle performance state for said main processor that is suitable for executing said identified instructions, said suitable non-idle performance state including an associated suitable clock frequency; and causing, by said look-ahead processor, said main processor to change clock frequency with which it executes instructions from a current clock frequency associated with a current non-idle performance state to a suitable clock frequency associated with said suitable non-idle performance state.