Browse Prior Art Database

Dynamic Trace Mechanism for Intelligent Terminals

IP.com Disclosure Number: IPCOM000045330D
Original Publication Date: 1983-Mar-01
Included in the Prior Art Database: 2005-Feb-06
Document File: 2 page(s) / 14K

Publishing Venue

IBM

Related People

Minshull, JF: AUTHOR [+2]

Abstract

In a network of intelligent terminals having a distributed virtual memory, a systems programmer is able, by remote control, to start and stop the tracing of program execution in any of the terminals, without requiring assistance (or even awareness) from the operators of those terminals. A distributed virtual memory terminal in which the trace mechanism can be built is described in European Patent Application 43391.

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Dynamic Trace Mechanism for Intelligent Terminals

In a network of intelligent terminals having a distributed virtual memory, a systems programmer is able, by remote control, to start and stop the tracing of program execution in any of the terminals, without requiring assistance (or even awareness) from the operators of those terminals. A distributed virtual memory terminal in which the trace mechanism can be built is described in European Patent Application 43391.

An intelligent terminal (such as the above-referenced distributed virtual memory terminal) provides an environment into which "application programs" can be loaded and within which these application programs are executed. This environment is typically realized by a "control program" held in read-only memory, and application programs are required to do their data input and output by invoking the services of this control program (even though application programs are usually unconstrained in the computations which they perform).

Accordingly, at selected points in the read-only microcode of the distributed virtual memory terminal, there are calls to a "dynamic trace" routine. Each call specifies one or more of 8 "event type" parameter bits, in order to distinguish between events such as "processing a keystroke" and "calling a transient". The dynamic trace routine maintains a "trace mask" byte in system storage. On each call to the dynamic trace routine, the caller's event-type parameter byte is ANDed with the trace mask byte, and if the result is zero, there is an immediate return to the caller and no trace action occurs. On system reset, the trace mask byte is initialized at zero to inhibit tracing, and in this state the CALLS to the trace routine with immediate RETURNS have no measurable effect on the execution time of the control program services.

A means is provided for a system programmer (who is assumed to have access to the backing store machine of the distributed virtual memory network) to send commands to a selected terminal to turn bits on and off in the trace mask byte, so enabling and disabling the tracing of selected events in that terminal. The action of tracing makes use of the virtual memory mechanism as follows. When a call to the dynamic trace routine finds that the specified event type is enabled for tracing, the dynamic trace routine writes a coded "trace message" into a "current trace message segment" in the terminal's virtual memory look- aside store (requesting a new trace message segment to be allocated in the virtual memory when the current trace message segment is full). Completed trace message segments are paged back to the backing store (using normal virtual memory procedures), at which point they can be extracted and decoded by the systems programmer.

The dynamic trace mechanism in the above referenced distributed virtual memory system can record any or all of the events listed below. For each event, the trace message contains an event type code,...