System Memory Cache Filtering Using Policy Identifiers
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Solution Overview
Problem
Current CPU cache management systems lack efficient mechanisms to filter and allocate cache lines based on utilization levels, leading to suboptimal performance due to unnecessary loading of underutilized cache lines, which increases bandwidth consumption and reduces cache efficiency.
Innovation Solution
The implementation of a method that uses policy identifiers to control cache operations, including cache line filtering and allocation, where cache lines with utilization levels below a threshold are prevented from being loaded into the system memory cache, utilizing techniques such as bloom filters and blacklist mechanisms to identify and exclude underutilized cache lines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If cache lines are loaded into system memory cache without filtering, then cache capacity is utilized, but bandwidth consumption increases and cache efficiency decreases
Solution Approach 1:
The patent applies preliminary action by implementing cache line filtering before loading cache lines into the system memory cache. The filter determines whether to load a cache line based on predicted utilization, preventing underutilized cache lines from being loaded in the first place. This proactive approach reduces unnecessary bandwidth consumption and improves cache efficiency by ensuring only potentially useful cache lines are loaded.
2Productivity
If all cache lines are loaded into system memory cache, then cache capacity is utilized, but unnecessary cache lines waste cache capacity
Solution Approach 1:
The patent implements self-service through feedback mechanisms where the system monitors actual cache line utilization and uses this information to refine filtering decisions. The filter learns from past cache line usage patterns and adjusts its predictions, allowing the system to automatically optimize cache capacity utilization without external intervention. This improves cache utilization while reducing waste by continuously adapting to actual usage patterns.
3Loss of energy
If cache line filtering is implemented, then bandwidth consumption is reduced, but system complexity increases
Solution Approach 1:
The patent applies the cheap short-living objects principle by using relatively simple filtering mechanisms that do not require complex, expensive hardware structures. The filter uses straightforward prediction algorithms and data structures that can be implemented with minimal additional hardware complexity. This approach reduces bandwidth consumption through filtering while keeping the increase in system complexity manageable and cost-effective.
Data Source
AI summary
Provided are methods, systems, and apparatus for managing and controlling memory caches, in particular, system level caches outside of those closest to the CPU. The processes and representative hardware structures that implement the processes are designed to allow for detailed control over the behavior of such system level caches. Caching policies are developed based on policy identifiers, where a policy identifier corresponds to a collection of parameters that control the behavior of a set of cache management structures. For a given cache, one policy identifier is stored in each line of the cache.