Phase-Constrained Node Reservations to Prevent Chip Network Starvation
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Solution Overview
Problem
Existing semiconductor computer chips with phase-based arbitration constraints face issues of node starvation due to unmanaged reservation policies, leading to processing delays when nodes are unable to transmit messages within a bounded time.
Innovation Solution
Implementing a reservation policy that allows processing nodes in a circular topology to make reservations for a given phase only once per reservation window, preventing multiple reservations in a phase window, and ensuring each node transmits at least once within a bounded time frame using a reservation mechanism.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If phase-based arbitration constraints are applied to manage destination processing between processing nodes, then message transmission order and destination processing are improved, but node starvation occurs when nodes are unable to transmit messages within a bounded time
Solution Approach 1:
The reservation mechanism allows a processing node to preliminarily secure a transmission opportunity in advance by placing a reservation on the reservation bus during a reservation window. This preliminary action guarantees that the node will be able to transmit its message within a bounded time frame, preventing node starvation while maintaining phase-based arbitration constraints.
2Productivity
If multiple reservations are allowed in a phase window, then nodes can transmit multiple messages efficiently, but reservation chaos occurs making it impossible to track and manage reservations
Solution Approach 1:
The reservation mechanism segments the transmission opportunities by creating distinct reservation windows and phase windows. Each reservation is confined to a specific reservation window and associated phase window, making it trackable and manageable. This segmentation allows multiple reservations to coexist without chaos, as each reservation is isolated to its designated time frame.
Solution Approach 2:
The system employs periodic reservation windows and phase windows that recur in a structured manner. Each reservation window is followed by a phase window, creating a periodic cycle that simplifies reservation tracking. This periodic structure ensures that reservations are made and executed in an organized sequence, preventing reservation chaos while maintaining high throughput.
3Speed
If standard message transmission is allowed without reservations, then message transmission is simple and fast, but nodes may be blocked indefinitely by other nodes with higher arbitration priority
Solution Approach 1:
Before transmitting a standard message, a processing node can preliminarily secure a transmission slot by placing a reservation during the reservation window. This preliminary reservation ensures that the node will not be blocked indefinitely by other nodes with higher arbitration priority, as the reserved slot is guaranteed for its transmission. This maintains simple and fast transmission while providing reliability guarantees.
Data Source
AI summary
A computer chip, a method, and computer program product for providing phase reservations between processing nodes. A computer chip includes a plurality of processing nodes interconnected in an on-chip data transfer network configured in a circular topology. The processing nodes include reservation mechanisms managing reservations made by processing nodes with phase constraints. The reservation policy allows the processing nodes to make a reservation, for a given phase, in any phase window, only once per reservation window. A reservation window can be a bounded amount of time for when a node is guaranteed an opportunity to transmit at least one message. The reservation policy also prevents the processing nodes from making more than one reservation in a phase window. Once a reservation is granted, the corresponding message may progress on the bus unimpeded. Requestors attempting to transmit messages are blocked until the message is transmitted.