Synchronization inside InnoDB frequently involves the use of spin loops (where, while waiting, InnoDB executes a tight loop of instructions repeatedly to avoid having the InnoDB process and threads be rescheduled by the operating system). If the spin loops are executed too quickly, system resources are wasted, imposing a relatively severe penalty on transaction throughput. Most modern processors implement the PAUSE instruction for use in spin loops, so the processor can be more efficient.
Beginning with 1.0.4, the InnoDB Plugin uses a PAUSE instruction in its spin loops on all platforms where such an instruction is available. This technique increases overall performance with CPU-bound workloads, and has the added benefit of minimizing power consumption during the execution of the spin loops.
Using the PAUSE instruction in InnoDB spin loops is transparent to the user. User does not have to do anything to take advantage of this performance improvement.