Cache Block Bounding Mechanism for Latency and Power Management
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Solution Overview
Problem
Current cache management systems face inefficiencies in reducing latency and conflict misses due to the lack of a finer limit on cache blocks associated with specific properties, which hinders power management and data allocation strategies.
Innovation Solution
Implementing a cache system with multiple partitions where a cache controller determines a bypass condition based on criteria such as write request fractions and memory access traffic to invalidate or store data accordingly, allowing for efficient allocation and power management by partitioning data types across active and inactive banks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the cache uses standard capacity or associativity limits, then the cache structure is simple, but the latency for searching and moving cache blocks with specific properties is large
Solution Approach 1:
The cache is divided into multiple sets, with each set containing multiple ways. Within each way, there are multiple cache blocks that can be independently managed. This segmentation allows the cache controller to operate on individual blocks with specific properties (coherence state, dirty state, ownership state) without affecting the entire cache, thereby reducing search and movement latency while maintaining a manageable structured organization.
Solution Approach 2:
The patent introduces a new dimension of control by adding block-level state attributes (coherence state, dirty state, ownership state) beyond the traditional set-way hierarchy. This enables selective manipulation of cache blocks based on these additional dimensions, allowing the system to quickly identify and move specific blocks without searching the entire cache, thus reducing latency without proportionally increasing structural complexity.
2Quantity of substance
If the cache allows more blocks with specific properties, then storage capacity is充分利用, but the latency to transition to low-power mode increases
Solution Approach 1:
The cache controller continuously monitors and tracks the state of individual cache blocks, maintaining metadata about coherence state, dirty state, and ownership state for each block. This preliminary organization of block information allows the system to quickly identify blocks that need to be evicted when transitioning to low-power mode, eliminating the need for time-consuming searches during the transition process itself.
Solution Approach 2:
The cache structure dynamically adapts to power management requirements by enabling selective eviction of blocks with specific properties. The controller can identify and move only the necessary blocks (e.g., dirty blocks, blocks with specific coherence states) rather than evacuating entire sets or ways, allowing the cache to maintain high utilization while achieving fast transitions to low-power modes when needed.
3Reliability
If the cache does not distinguish requests associated with specific properties, then the cache allocation is simple, but conflict misses increase significantly
Solution Approach 1:
The cache allocation strategy applies different handling rules to cache blocks based on their local properties (coherence state, dirty state, ownership state). Instead of treating all blocks uniformly, the controller can selectively replace blocks with specific properties, such as preferring to evict clean blocks over dirty blocks, or blocks without ownership over blocks with ownership. This localized differentiation improves hit rates by keeping important blocks in the cache while adding only modest complexity to the allocation logic.
Data Source
AI summary
A system and method for efficiently limiting storage space for data with particular properties in a cache memory. A computing system includes a cache array and a corresponding cache controller. The cache array includes multiple banks, wherein a first bank is powered down. In response a write request to a second bank for data indicated to be stored in the powered down first bank, the cache controller determines a respective bypass condition for the data. If the bypass condition exceeds a threshold, then the cache controller invalidates any copy of the data stored in the second bank. If the bypass condition does not exceed the threshold, then the cache controller stores the data with a clean state in the second bank. The cache controller writes the data in a lower-level memory for both cases.