Memory Controller Arbitration for Multi-Rank Request Scheduling
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Solution Overview
Problem
The performance of memory systems is deteriorated when memory operations are controlled based on requests from a host, particularly in systems with multiple ranks, requiring an efficient scheduling method to manage switching between ranks.
Innovation Solution
A memory controller with a request buffer, arbiter, and command generator that prioritizes and schedules requests based on type and rank, ensuring commands are issued in a descending priority order to minimize intervals between operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If memory operations are executed based on the order of requests from the host, then the system maintains simple request processing, but the memory system performance deteriorates due to inefficient rank switching
Solution Approach 1:
The arbiter pre-determines the priority of requests before they are fully processed by the command generator. By assigning priorities (A, B, C, D categories) in advance based on request type and rank information, the system prepares the execution sequence beforehand, avoiding performance deterioration from inefficient rank switching while maintaining organized request handling
Solution Approach 2:
The request scheduling system dynamically adjusts the execution order based on the specific characteristics of each request (type and rank). Instead of a fixed processing order, the arbiter continuously evaluates and re-prioritizes requests in the buffer, allowing the system to adapt to varying workload patterns and optimize performance for different scenarios
2Productivity
If the memory controller processes requests in FIFO order, then the request processing is simple, but the intervals between operations increase reducing efficiency
Solution Approach 1:
The system changes the parameter of request execution order from simple FIFO (first-in-first-out) to priority-based ordering. By introducing priority levels (A, B, C, D) that consider request type and rank, the arbiter reorders requests to minimize idle intervals and optimize the timing of operations across different ranks, thereby reducing operation intervals and increasing throughput
3Productivity
If the arbiter issues requests without priority scheduling, then the system operation is straightforward, but rank switching efficiency deteriorates
Solution Approach 1:
The arbiter segments requests into distinct priority categories (A, B, C, D) based on their type and rank characteristics. This segmentation allows the arbiter to handle different request types systematically, improving rank switching efficiency by ensuring that requests requiring rank transitions are properly prioritized and executed in an optimized sequence
Data Source
AI summary
A memory controller includes: a request buffer storing read and write requests of a first rank, and read and write requests of a second rank; an arbiter determining a first request and second requests among the stored requests, the second requests to be issued after the first request according to a descending priority, such that a B request has a higher priority than a C request among the second requests; and a command generator generating commands to be issued to the first rank and the second rank according to the issue order of the first and second requests, wherein the B request is a command whose type and rank are different from those of the first request, and wherein the C request is a command whose type is the same as the type of the first request and whose rank is different from the rank of the first request.