International Business Machines Corporation

Gregory Bollella

Soumitra Sarkar

Peter Frederick Haggar

Diane Phylis Pozefsky

David Mark Wendt

Vachaspathi Peter Kompella

James A Mickelson

Kathleen Marie Hogan

Alisa Lynn Morse

The present invention provides a method, system, and computer program product for improving scheduling of tasks in systems that accumulate execution time. An upper bound is computed on the amount of additional time each schedulable task in the system may continue to execute after exceeding its predetermined cost, without adversely affecting overall operation of the system (that is, ensuring that the continued execution will not cause invocations of subsequent tasks to fail to meet their execution deadlines). By allowing tasks to run longer, the potential that the task will successfully end is increased, thereby yielding a more efficient overall system. In the preferred embodiment, the extensions are iteratively computed as a fixed percentage of the cost of each task until reaching an amount of time where the system is no longer feasible. The extension values resulting from the iteration before the cost-extended system becomes infeasible are then used at run-time when a particular task encounters an overrun condition. This technique is advantageous in systems where execution of non-schedulable entities (such as occurrence of hardware interrupts) occurs during execution of one or more of the scheduled tasks.

System for incrementally computing the maximum cost extension allowable for subsequent execution of each task using fixed percentage of the associated cost

A method of supporting real-time computing within a general purpose operating system, by supporting co-resident operating systems. This is a methodology for allowing existing, well-understood real-time systems technology to co-exist with commercial, general purpose operating systems to support applications such as desktop multimedia conferencing. The approach is to partition the central processor and other system resources into two virtual machines, first a machine running a largely unmodified general purpose operating system, and second a machine running a real-time kernel, then to multiplex access to the physical hardware by the virtual machines.

System and method for supporting real-time computing within general purpose operating systems

The present invention provides a method, system, and program product for sharing resources between real-time and non-real-time (or general purpose) programs in a computer system which utilizes Slotted Priority Architecture. Non-pre-emptable, internally triggered resources are shared using the method of the present invention. The real-time scheduler anticipates upcoming realtime minor cycles and, using knowledge of which resources are to be used by the next scheduled real-time task and of the latency times of the resources to be used, signals the device drivers for the resources to be used to stop accepting requests from general purpose tasks far enough in advance to the beginning of the real-time minor cycles that will utilize them to ensure that the resources will be idle and available for the real-time tasks to use without delay.

Resource sharing between real-time and general purpose programs

In order to more fully support the need to interconnect dissimilar networks, methods and apparatus are set forth which allow a transport gateway between a native (SNA/APPN) network and a mixed or non-native network to preserve the dynamic functions of the native network. The functions of fully dynamic directory and route selection are supported, in addition to the ability to use parallel gateways when connecting a native network to a mixed network. The ability to route information through a gateway from a dependent LU requester in a non-native network to a dependent LU server in a SNA/APPN network is also demonstrated. This allows concatenation of native and non-native networks while maintaining the addressability and accessibility of the native network.

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Durham, NC, United States of America

Gregory Bollella