NoC Input Switching Device for Head-of-Line Blocking
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Solution Overview
Problem
The Network on Chip (NoC) system experiences throughput degradation due to the 'Head of Line Blocking Problem', where buffers in routers become full when flits are successively input through one path, preventing subsequent flits from being received until free space is generated.
Innovation Solution
The implementation of a specific router with an input switching device that includes multiple buffers and a controller, which selectively sets the output destination of flits based on the free space of other buffers, allowing flits to be transferred directly between adjacent routers or IPs without involving the main router, thereby dispersing the load and preventing congestion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If flits are successively input through one path in a router, then the buffer corresponding to that path becomes full, but subsequent flits cannot be received until free space is generated, causing throughput degradation
Solution Approach 1:
The invention divides the router's buffer resources into multiple independent buffer groups, where each group can be independently selected as an output destination. This segmentation allows flits to be routed to different buffer groups based on availability, preventing a single buffer from becoming a bottleneck and enabling continuous data flow even when some buffers are full.
Solution Approach 2:
The invention implements dynamic buffer selection where the output destination of flits is not fixed but can be changed based on real-time buffer status. The system dynamically identifies buffers with free space and redirects flits to those buffers, allowing the routing structure to adapt to changing traffic conditions and prevent head-of-line blocking.
2Ease of operation
If all flits are routed through the main router, then routing control is centralized, but buffer congestion occurs and throughput degrades
Solution Approach 1:
The invention introduces buffer groups as intermediary structures between the main router and final destinations. These buffer groups act as intermediate storage points that can be selectively used to bypass the main router's buffer congestion, allowing flits to be transferred directly between adjacent routers or IPs without involving the main router when appropriate.
3Quantity of substance
If multiple buffers are provided in the router, then flit storage capacity increases, but buffer management complexity increases
Solution Approach 1:
The invention makes buffer groups serve multiple functions: they act as both temporary storage buffers and as selectable output destinations for flit transmission. This multi-functionality reduces the need for separate management mechanisms and simplifies buffer management while increasing effective storage capacity and routing flexibility.
Data Source
AI summary
An input switching device is provided between a plurality of functional blocks (NoC routers or IP) connected to a specific router among a plurality of NoC routers of a NoC system and the specific router. The specific router includes a plurality of first buffers that temporarily store flits from the input switching device. A plurality of second buffers in the input switching device correspond to the respective one of the plurality of functional blocks, and temporarily store the flits from the functional block. A controller selectively sets one of the plurality of first buffers as output destination of the flit stored in each of the second buffers based on a free space of the plurality of first buffers. A distributor outputs the flit stored in each of the second buffers to output destination set for the flit by the controller. In this way, throughput degradation of the NoC system can be prevented.