Enhanced Tag Pool Decouples Cache Reuse and Latency

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Solution Overview

Problem

Conventional cache designs are limited in independently optimizing cache reuse and latency tolerance due to the one-to-one correspondence between tags and cachelines, requiring additional tags and hardware resources even if fewer tags could suffice for cache reusability.

Innovation Solution

Implementing a pool of independent enhanced tags that can associate with multiple cachelines, allowing for separate optimization of tag reusability and latency tolerance, with a tag repository and cacheline repository decoupled from each other, reducing resource consumption and comparator requirements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a one-to-one correspondence between tags and cachelines is implemented, then cache structure is simple and management is easy, but cache reuse and latency tolerance cannot be independently optimized

Engineering Contradiction:

Improveindependent optimization capabilityVSAvoidtag-cacheline structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent segments the traditional unified tag-cacheline structure into two independent components: a pool of enhanced tags and a pool of cachelines. This segmentation allows independent optimization of tag reusability and latency tolerance, as each component can be sized and managed separately based on specific performance requirements.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The enhanced tag structure serves multiple functions: it can match multiple cachelines simultaneously and support both cache reuse and latency tolerance optimization. The enhanced tag includes a match portion for address comparison and a data locator portion for identifying cachelines, enabling versatile cache management operations.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If additional cachelines are added to achieve acceptable latency tolerance, then latency tolerance improves, but the number of tags and hardware resources must increase proportionally

Engineering Contradiction:

Improvelatency toleranceVSAvoidnumber of tags

Core Design Contradiction:

ReliabilityVSQuantity of substance

Solution Approach 1:

Each enhanced tag can serve multiple cachelines simultaneously through its data locator portion, which identifies one or more cachelines associated with the tag. This multi-functionality allows a smaller number of tags to support a larger number of cachelines, improving latency tolerance without proportionally increasing tag count.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent implements dynamic association between enhanced tags and cachelines through the cacheline access controller, which can assign and reassign cachelines to tags based on usage patterns and availability. This dynamic management allows efficient utilization of tags across multiple cachelines, reducing the total number of tags needed.

Inventive Principle:

Principle #15Dynamics

3Quantity of substance

If the number of tags is reduced to optimize cache reuse, then resource consumption decreases, but latency tolerance may be compromised

Engineering Contradiction:

Improvenumber of tagsVSAvoidlatency tolerance

Core Design Contradiction:

Quantity of substanceVSReliability

Solution Approach 1:

The patent adds a new dimension to tag functionality by including a data locator portion that references cacheline identifiers. This additional dimension allows a single tag to map to multiple cachelines, enabling reduced tag count while maintaining adequate latency tolerance through enhanced tag reusability across multiple cachelines.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

4Adaptability or versatility

If a pool of independent enhanced tags is implemented, then tag reusability and latency tolerance can be independently optimized, but tag structure and access control become more complex

Engineering Contradiction:

Improveindependent optimization capabilityVSAvoidenhanced tag structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The enhanced tag is segmented into distinct functional portions: a match portion for address comparison and a data locator portion for cacheline identification. This segmentation organizes the complexity into manageable, functionally distinct components that can be independently optimized and managed.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS7796137B1Enhanced tag-based structures, systems and methods for implementing a pool of independent tags in cache memories

Publication Date: 2010.09.14 NVIDIA CORP

AI summary

Disclosed are an apparatus, a system, a method, a graphics processing unit (“GPU”), a computer device, and a computer medium to implement a pool of independent enhanced tags to, among other things, decouple a dependency between tags and cachelines. In one embodiment, an enhanced tag-based cache structure includes a tag repository configured to maintain a pool of enhanced tags. Each enhanced tag can have a match portion configured to form an association between the enhanced tag and an incoming address. Also, an enhanced tag can have a data locator portion configured to locate a cacheline in the cache in response to the formation of the association. The data locator portion enables the enhanced tag to locate multiple cachelines. Advantageously, the enhanced tag-based cache structure can be formed to adjust the degree of reusability of the enhanced tags independent from the degree of latency tolerance for the cacheline repository.