DMA Engine Descriptor List for Noncontiguous Memory
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Solution Overview
Problem
Conventional DMA engines are unable to efficiently handle noncontiguous source and destination memory addresses, requiring multiple commands to move data, which increases latency and processing overhead.
Innovation Solution
Implementing a memory sub-system that allows DMA commands to specify noncontiguous memory addresses using vector data types or linked lists, enabling a single command to manage multiple memory locations, thereby reducing the need for multiple commands and improving processing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional DMA engines are used to handle noncontiguous memory addresses, then data can be moved between memory locations, but multiple separate commands are required which increases latency and processing overhead
Solution Approach 1:
The patent merges multiple separate DMA commands into a single unified DMA command by introducing a descriptor list structure. Each descriptor in the list represents a different memory region (source or destination), and the DMA engine processes all regions sequentially within one command execution. This combining approach eliminates the overhead of multiple command submissions and completions, directly reducing latency while maintaining the ability to handle noncontiguous memory addresses.
Solution Approach 2:
The patent segments the memory address space into multiple distinct regions, each represented by a descriptor in the descriptor list. Each descriptor contains information about a specific source or destination memory region including base address, length, and direction. This segmentation allows the single DMA command to efficiently manage multiple noncontiguous memory regions without requiring separate commands for each region.
2Adaptability or versatility
If multiple DMA commands are used to move data to noncontiguous memory locations, then all data can be transferred, but the processing overhead and complexity increase
Solution Approach 1:
The patent creates a universal DMA command structure that can handle both contiguous and noncontiguous memory addresses through the descriptor list mechanism. The same single-command interface adapts to different scenarios: when descriptors point to contiguous regions, it behaves like a traditional DMA command; when descriptors point to noncontiguous regions, it efficiently manages scatter-gather operations. This multi-functionality maintains flexibility while reducing complexity compared to requiring different command types.
Solution Approach 2:
The descriptor list acts as an intermediary between the host system and the DMA engine. Instead of the host submitting multiple separate commands, it submits a single command with a descriptor list that fully describes all memory regions. The DMA engine uses this intermediary structure to coordinate the complex sequence of read and write operations across multiple noncontiguous regions, simplifying the host interface while enabling sophisticated data movement patterns.
Data Source
AI summary
A processing device, operatively coupled with a plurality of memory devices, is configured to receive a DMA command for a plurality of data sectors to be moved from a source memory region to a destination memory region, the destination memory region comprises a plurality of noncontiguous memory addresses and the DMA command comprises a destination value referencing the plurality of noncontiguous memory addresses. The processing device further retrieves the plurality of noncontiguous memory addresses from a location identified by the destination value. The processing device then reads the plurality of data sectors from the source memory region. The processing device also performs, for each respective data sector of the plurality of data sectors associated with the DMA command, a write operation to write the respective data sector into a corresponding respective noncontiguous memory address from the plurality of noncontiguous memory addresses of the destination memory region.