Apparatus, method and computer program for monitoring performance of software

A method for monitoring performance of software executing on processing circuitry, comprising:

• employing a plurality of event counters to maintain respective count values based on monitoring of events occurring during execution of a sequence of instructions of the software by the processing circuitry;
• at least when a given condition is present, being responsive to a given instruction in the sequence whose execution by the processing circuitry will cause a number of operations to be performed that is dependent on associated instruction control information, where one or more of the operations are associated with a given event being monitored by a given event counter:
• to apply a selection algorithm to derive a selected update indicator from the instruction control information, where the selection algorithm is such that the selected update indicator varies over multiple applications of the selection algorithm;
• to cause the count value of the given event counter to be adjusted by a default amount to account for execution of the given instruction by the processing circuitry, when a value of the selected update indicator is a first value;
• and
• to cause the count value of the given event counter to be adjusted by a non-default amount to account for execution of the given instruction by the processing circuitry, when the value of the selected update indicator is a second value.

A non-transitory computer-readable storage medium storing a computer program comprising instructions which, when executed by a host data processing apparatus, control the host data processing apparatus to provide an instruction execution environment for executing target program code, the computer program comprising:

• event counting program logic to emulate a plurality of event counters, each to maintain a respective count value based on monitoring of events occurring during simulated execution of a sequence of instructions of the target program code by processing program logic;
• selection program logic arranged, at least when a given condition is present, to be responsive to a given instruction in the sequence whose execution by the processing program logic will cause a number of operations to be performed that is dependent on associated instruction control information, where one or more of the operations are associated with a given event being monitored by a given event counter, to apply a selection algorithm to derive a selected update indicator from the instruction control information, where the selection algorithm is such that the selected update indicator varies over multiple applications of the selection algorithm;
• count control program logic arranged, at least when the given condition is present, to be responsive to the given instruction to:
• cause the count value of the given event counter to be adjusted by a default amount to account for execution of the given instruction by the processing program logic, when a value of the selected update indicator is a first value;
• and
• cause the count value of the given event counter to be adjusted by a non-default amount to account for execution of the given instruction by the processing program logic, when the value of the selected update indicator is a second value.