Cache Segment Reinsertion Scoring for Hit Rate
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Solution Overview
Problem
Conventional cache eviction policies based solely on recency are ineffective for coarse-granularity cache management, leading to the removal of relevant data and decreased cache hit rates, as they fail to accurately assess the relevance of data within cache units.
Innovation Solution
Implement a cache management system that scores cache units based on multiple criteria such as segment validity, age, priority, access count, and hotness, and copies relevant segments from evicted cache units to maintain data relevance, thereby optimizing cache performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional LRU eviction policy is used for coarse-granularity cache management, then cache unit eviction is simplified, but relevant data is removed and cache hit rate decreases
Solution Approach 1:
The patent segments the cache unit into multiple segments and applies different eviction criteria to each segment. Instead of treating the entire cache unit as a single entity, it divides it into segments that can be independently evaluated and evicted based on their individual relevance scores, thereby preventing removal of relevant data while maintaining manageable complexity
Solution Approach 2:
The patent applies local quality by assigning different eviction priorities and criteria to different segments within a cache unit. Each segment is evaluated individually based on its access patterns and relevance, allowing the system to evict only the least relevant segments while preserving valuable data in other segments of the same cache unit
2Device complexity
If cache units are evicted at coarse granularity, then SSD erasure operations are simplified, but data relevance cannot be accurately assessed
Solution Approach 1:
The patent segments the cache unit into smaller manageable segments that can be individually assessed for relevance. This segmentation allows the system to maintain coarse-grained erasure operations for SSD compatibility while implementing fine-grained relevance assessment at the segment level, resolving the contradiction between operational simplicity and measurement precision
Solution Approach 2:
The patent introduces a new dimension of segment-level relevance scoring alongside the traditional cache unit-level eviction approach. By adding this hierarchical dimension, the system can perform coarse-grained erasure operations while simultaneously conducting precise relevance assessment at the segment level, thereby improving data relevance measurement without complicating the erasure process
3Reliability
If segments are copied from evicted cache units, then data relevance is maintained, but system complexity increases
Solution Approach 1:
The patent performs preliminary action by calculating relevance scores for all segments before eviction occurs. This pre-scoring allows the system to identify and preserve relevant segments in advance, enabling selective copying only when necessary and avoiding the need for complex real-time analysis during eviction operations
Solution Approach 2:
The patent applies copying by replicating relevant segments from evicted cache units to surviving cache units. This copying mechanism preserves data relevance by ensuring that important segments are duplicated and maintained in the cache, rather than being permanently lost during the eviction process
Data Source
AI summary
A data processing system and methods for performing cache eviction are disclosed. An exemplary method includes maintaining a metadata set for each cache unit of a cache device comprising a plurality of cache units, each cache unit having a plurality of segments. In response to determining that a cache eviction is to be performed, a cache unit is evicted based on its metadata set. The exemplary method includes selecting one or more segments of the evicted cache unit to copy to a second cache unit based on the metadata set of the evicted cache unit, copying the selected one or more segments to the second cache unit, and writing the second cache unit to a storage device. The metadata set may include deletion hints (DH) to indicate valid segments, last access time (LAT) or age based metadata, an access count, or a score for each segment based on the metadata set.