Cisco Technology, Inc.

There, Inc.

Kenneth J Duda

David R Cheriton

William D Harvey

A scheduling mechanism that fairly allocates a resource to a number of schedulable elements, of which some are latency-sensitive, is disclosed. Each element's use of the resource is tracked by determining the element's virtual time. An active element is selected from the elements that are ready to use the resource by determining the element that has the smallest effective virtual time. The effective virtual time is the element's actual virtual time modified by a borrowed virtual time value. When an element has a short-term need for the resource, it can borrow the privilege to run by borrowing virtual time. As the element uses the resource, it consumes virtual time according to its weight. When the elements are scheduled for the resource, the ready element having the smallest virtual time is selected. The invention enforces long-term fairness to each element while allowing latency-sensitive elements to be preferably selected.

Method, apparatus and computer program product for borrowed-virtual-time scheduling

The present invention includes a scheduling mechanism that fairly allocates a resource to a number of schedulable elements of which some are latency-sensitive. The invention tracks each element's use of the resource by determining the element's virtual time. An active element is selected from the elements that are ready to use the resource by determining the element that has the smallest effective virtual time. The effective virtual time is the element's actual virtual time modified by a borrowed virtual time value. When an element has a short-term need for the resource, it can borrow the privilege to run by borrowing virtual time. As the element uses the resource, it consumes virtual time according to its weight. When the elements are scheduled for the resource, the ready elements having the smallest virtual time is selected. The invention enforces long-term fairness to each element while allowing latency-sensitive elements to be preferably selected.

A set of mechanisms provides consistency, responsiveness, and integrity, to allow high-realism in a distributed network simulation environment. Consistency is achieved by executing the same computation with the same inputs on multiple machines. Responsiveness is achieved by executing the parts of the computation that affect the user's object earlier on the user's machine than on the server for the user's object. Integrity is achieved by executing all computations authoritatively on the server. The ability to run different parts of a shared computation at varying times on different machines is provided.

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Hillsborough, CA, United States of America

Kenneth J Duda