A sampling based DBR framework which leverages a separate core for program analysis. The framework includes a hardware performance monitor, a DBR service that executes as a separate process and a lightweight DBR agent that executes within a client process. The DBR service aggregates samples from the hardware performance monitor, performs region selection by deducing the program structure around hot samples, performs transformations on the selected regions (e.g. optimization), and generates replacement code. The DBR agent then patches the client process to use the replacement code.