Dynamic Cache Indexing Function Selection
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Solution Overview
Problem
Modern computer systems face performance issues due to large latencies in main memory structures, which are exacerbated by cache misses caused by ineffective indexing functions in cache architectures, leading to underutilization and overutilization of cache resources.
Innovation Solution
Implementing a plurality of indexing functions that can be chosen and used dynamically based on the specific needs of a computer program to optimize cache performance, either through hardwired specialized hardware or customizable lookup tables, allowing for improved mapping of main memory addresses to cache locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single indexing function is used in cache architecture, then the cache design is simple, but cache performance deteriorates due to cache conflicts and misses
Solution Approach 1:
The patent implements dynamic indexing function selection where the cache can switch between multiple indexing functions (e.g., bit selection, set associative, fully associative) based on the access patterns of different programs or program portions. This dynamic adaptation allows the cache to optimize performance for varying workloads without permanently increasing structural complexity
Solution Approach 2:
The patent changes the indexing function parameter based on program characteristics and cache performance metrics. By monitoring cache miss rates and switching between different indexing functions (changing the mapping parameter), the system achieves improved cache performance without requiring a fundamentally complex cache structure
2Productivity
If cache size is increased to reduce conflicts, then cache performance improves, but memory latency and system cost increase
Solution Approach 1:
Instead of increasing cache size, the patent changes the indexing function parameter to reduce cache conflicts. By switching between different indexing functions (e.g., from bit selection to set associative), the system achieves better cache utilization and reduced misses without the latency penalty of larger cache structures
3Productivity
If associativity of cache is increased to allow addresses to be placed in multiple locations, then cache misses reduce, but design complexity and cost increase significantly
Solution Approach 1:
The patent implements dynamic associativity selection where the cache can switch between different associativity modes (direct-mapped, set-associative, fully-associative) based on program behavior. This allows the system to achieve high miss reduction when needed while maintaining simple direct-mapped behavior for other cases, avoiding permanent complexity increase
Solution Approach 2:
The patent segments the cache into multiple ways or sets that can be independently configured with different indexing functions. This segmentation allows different portions of the cache to use different associativity levels simultaneously, achieving high performance for specific workloads while maintaining overall design simplicity
4Device complexity
If bit selection indexing function is used for simplicity, then cache design is straightforward, but cache conflicts occur causing underutilization and overutilization of cache locations
Solution Approach 1:
The patent dynamically selects between bit selection and other indexing functions based on program characteristics and cache performance. When bit selection causes excessive conflicts, the system switches to alternative functions, maintaining simplicity while improving utilization efficiency through adaptive behavior
Solution Approach 2:
The patent changes the indexing function parameter from fixed bit selection to dynamically selectable functions. By monitoring cache conflict rates and switching to alternative indexing functions when conflicts exceed thresholds, the system achieves better utilization without permanently complicating the indexing mechanism
Data Source
AI summary
Methods and apparatus related to memory indexing. Receiving indications of an indexing function for use with a memory. Performing indexing functions with a processor before addressing a memory location. Referencing a customizable lookup table to determine a memory location. Translating a computer program to control a computer system to use a desired indexing function. Determining desired indexing functions based on performance of a computer system.