Dynamic computer performance monitor

An apparatus for monitoring the performance of a computer system comprising:

• a compiler for generating an uninstrumented program, the uninstrumented program including a candidate instruction at an address selected for performance monitoring;
• means for generating an instrumented program from the uninstrumented program, the instrumented program including an instrumentation instruction at the address selected for performance monitoring, the instructions of the uninstrumented program and the instructions of the instrumented program stored at identical relative memory addresses;
• a first set of paging values mapping the uninstrumented program into a memory of the computer system;
• a second set of paging values to map the instrumented program and an instrumentation routine into the memory of the computer system, the instrumentation routine to be called by the instrumentation instruction;
• means, responsive to a signal while executing the uninstrumented program, for activating the second set of paging values to execute the instrumented program.

A method for executing a computer program, comprising the steps of:

• activating the execution of an uninstrumented program;
• prior to completion of the execution of the activated uninstrumented program, activating an instrumented program having an instrumentation routine for routing the execution flow to a plurality of instrumentation procedures;
• and
• upon completion of the instrumentation routine, reactivating execution of the uninstrumented program.