GB1513946A - Data processing systems - Google Patents

Abstract

1513946 Monitoring program execution SIEMENS AG 25 June 1975 [3 July 1974] 26850/75 Heading G4A To monitor the execution of an application program in a data processing system one instruction in each linear program section, i.e. a section which is executed sequentially with no jumps etc., is replaced by a respective sampling command, the replaced instruction being stored in a respective part of the system store, each sampling command when executed causing execution of the replaced instruction and the storage of an acknowledgement thereof thereby to monitor whether and how often the replaced instruction is executed. The arrangement allows possible faults to be detected, e.g. one replaced command and thus its corresponding program section is never executed or is executed with an unusually high frequency, without incurring the large time penalty involved, e.g. when a tracing program is used which monitors the execution of every instruction in the monitored program, and without requiring excessive storage space for storing the monitoring results. The system is programmed to receive from an input device the addresses of instructions in the application program which are to be replaced and to replace the specified instructions by the sampling commands, the replaced instruction being stored in an assigned area of the system program store. The results of the monitoring are stored in a result store which may be part of the system program store in one of several forms and may be printed out. In a first form the results are stored in the form of a list of the addresses or numbers of the sampling commands. Alternatively entries may be made in the program store, each entry including a replaced instruction, an indication of the corresponding sampling command or its addtess, and a binary count indicating the number of times the command has been executed. In response to print out of the results, and where a fault is suspected a full tracing program may be run in respect of the corresponding program section. Each sampling command, when executed, triggers a jump to a sub-program which, inter alia, accesses and executes the replaced instruction and stores the acknowledgment. The jump may be effected by a conventional jump instruction or by mutually modifying the priority of the subprogram or application program. When no further monitoring is required the replaced instructions may be reinstated by a suitable program.