Cache Dirty-State Retention Through Dynamic Replacement Policies

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Solution Overview

Problem

Managing dirty data in cache memories is challenging due to the need to determine which agent should retain or pass the dirty state, leading to inefficient writebacks and increased power consumption.

Innovation Solution

Implementing a cache replacement policy circuit that dynamically decides whether to pass or retain the dirty state based on the replacement policy information, using existing cache replacement policies to defer writebacks and optimize data management.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the dirty state is retained in the snoopee cache, then the number of memory writebacks is reduced, but the cache memory usage increases and may cause cache evictions

Engineering Contradiction:

Improvewriteback efficiencyVSAvoidcache memory usage

Core Design Contradiction:

ProductivityVSQuantity of substance

Solution Approach 1:

The patent implements a dynamic state transition mechanism where the dirty state can be retained in the snoopee cache based on real-time cache status and access patterns. The system dynamically decides whether to maintain the dirty state or trigger a writeback, adapting to changing cache conditions rather than following a fixed protocol

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the state parameter of the cache line by allowing the dirty state to be retained in the snoopee cache. This parameter change enables the snoopee to hold modified data without immediately writing back to memory, thereby reducing writeback operations while managing cache occupancy through state management

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the dirty state is passed to the requestor, then the requestor can manage the data, but additional memory writebacks occur and power consumption increases

Engineering Contradiction:

Improvedata management flexibilityVSAvoidpower consumption

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent implements a feedback mechanism where the snoopee evaluates its cache status, replacement policy, and the nature of the read request before deciding whether to retain or pass the dirty state. This feedback loop prevents unnecessary state transitions that would trigger writebacks and increase power consumption

Inventive Principle:

Principle #23Feedback

3Productivity

If cache replacement policy is used to decide dirty state management, then writebacks are deferred and performance improves, but the complexity of cache management increases

Engineering Contradiction:

Improveprocessor performanceVSAvoidcache management complexity

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent makes the cache replacement policy multi-functional by using it for both its traditional purpose (managing cache evictions) and an additional purpose (deciding dirty state retention). This universal application of the replacement policy avoids adding separate management logic, thereby limiting the increase in complexity while achieving deferred writebacks

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS12386753B2Systems and methods for managing dirty data

Publication Date: 2025.08.12 MICROSOFT TECHNOLOGY LICENSING LLC

AI summary

Embodiments of the present disclosure include techniques for managing dirty data. An agent receives a request for data. If the data is dirty data, the agent may use a replacement policy to determine if the data should be passed clean or dirty to the requestor. The replacement policy may correspond to how long the dirty data being stored in a cache line is to be maintained. In one embodiment, the replacement policy is a circuit, such as an SRAM and a logic circuit, for example.