Compressed Cache Layout With Sideband Metadata for Bandwidth Limits
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Solution Overview
Problem
Data processing systems, particularly graphics processing systems, face challenges in managing storage and bandwidth requirements due to the need to handle uncompressed data, which can lead to performance issues, especially in resource-constrained mobile devices.
Innovation Solution
A cache system that stores data in a compressed form, with associated compression metadata provided as separate side band data, allowing for efficient decoding and encoding operations within the cache, thereby reducing the need for extensive memory transactions and optimizing cache utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If data is stored in uncompressed form in external memory, then data access speed is improved, but storage bandwidth requirements and power consumption increase
Solution Approach 1:
The patent segments data into compressed blocks with associated metadata, allowing selective decompression of only the portions needed for processing. This reduces the amount of data transferred between external memory and the processor, thereby reducing power consumption while maintaining access speed for the required data segments.
Solution Approach 2:
The patent performs preliminary compression of data before storing it in external memory, and maintains compression metadata that enables rapid identification and decompression of only the necessary data blocks. This preliminary preparation reduces the frequency and volume of data transfers, lowering power consumption while preserving access speed.
2Quantity of substance
If data is compressed before storage, then storage bandwidth requirements are reduced, but additional decompression operations are required
Solution Approach 1:
The patent introduces compression metadata as an intermediary structure that sits between the compressed data blocks and the processing units. This metadata contains information about data organization, compression parameters, and access patterns, enabling efficient decompression without requiring complex processing logic. The metadata acts as a guide that simplifies the decompression process while maintaining reduced data volume.
3Ease of operation
If compression metadata is stored with data blocks, then data organization is simplified, but cache line utilization decreases due to wasted space
Solution Approach 1:
The patent extracts compression metadata from the data blocks themselves and stores it separately in a dedicated metadata structure. This separation allows data blocks to be stored in cache lines without the overhead of embedded metadata, maximizing cache line utilization. The metadata is organized independently to maintain ease of access and data organization, while cache efficiency is improved by eliminating wasted space in cache lines.
4Reliability
If data is transferred frequently between external memory and processor, then data availability is improved, but power consumption and bandwidth requirements increase
Solution Approach 1:
The patent implements a nested structure where compressed data blocks are organized within a hierarchical memory system, with compression metadata providing the nesting framework. This allows the system to maintain data availability by keeping compressed data in external memory while enabling rapid access through the metadata structure, reducing the need for frequent full data transfers and thereby lowering power consumption.
Data Source
AI summary
A data processing system is provided comprising a cache system configured to transfer data between a processor and memory system. The cache system comprises a cache. When a block of data that is stored in the memory in a compressed form is to be loaded into the cache, the block of data is stored into a group of one or more cache lines of the cache and the associated compression metadata for the compressed block of data is provided as separate side band data.