Patent ID: 8260991

Claim:
A data processing apparatus for performing transactions, comprising: initiator circuitry configured to initiate said transactions; recipient circuitry configured to handle each transaction initiated by the initiator circuitry; a communication path configured to interconnect the initiator circuitry and the recipient circuitry via which the transactions are propagated between the initiator circuitry and the recipient circuitry; and measurement circuitry, coupled to said communication path, configured to measure a value of predetermined property of the transactions propagated over said communication path, said measurement circuitry comprising: active transaction count circuitry configured to determine, from transaction information passing over the communication path, an indication of the number of transactions in progress; accumulator circuitry configured to maintain an accumulator value, the accumulator circuitry increasing the accumulator value dependent on said indication of the number of transactions in progress from said active transaction count circuitry; and a value register configured to maintain an estimate of the value of said predetermined property, wherein, the accumulator circuitry is further configured to decrease the accumulator value dependent on said estimate currently stored in the value register, and the value register is further configured to update the estimate stored in the value register dependent on the current accumulator value such that said decrease in the accumulator value and said update of said estimate are performed each time a transaction in progress reaches a predetermined point.