Cache Dirty Data Management via High-Priority Clean Notifications
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Solution Overview
Problem
In memory management systems, particularly in Level 2 cache memory, the presence of dirty data can lead to inefficiencies as it occupies substantial memory space, causing read and write operations to stall until memory space becomes available, which is problematic for applications requiring high data throughput.
Innovation Solution
A method is introduced where a tag look-up unit processes commands by extracting set, tag, and sector identifiers from memory addresses, determining cache line association, and transmitting high-priority clean notifications to the frame buffer logic when a pre-determined threshold of dirty data is reached, allowing for preemptive retrieval of dirty data and reduction of read/write stalls.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If dirty data is retained in the L2 cache until cleaning is complete, then data coherency is maintained, but memory space becomes occupied and read/write operations stall
Solution Approach 1:
The patent implements a high-priority clean mechanism that proactively initiates dirty data cleaning operations when the number of dirty cache lines reaches a threshold, rather than waiting for cache full conditions. This preliminary action prevents future stalls by clearing space before it is needed, maintaining both coherency and throughput.
Solution Approach 2:
The system monitors the number of dirty cache lines and uses this feedback to trigger high-priority clean operations when thresholds are reached. This closed-loop control ensures that cleaning occurs at appropriate moments to prevent stalls while maintaining data coherency.
2Productivity
If memory space is allocated for read operations, then read throughput is improved, but the space remains unusable until result data is received from external memory
Solution Approach 1:
The system proactively allocates memory space for pending read operations in advance, rather than waiting for external memory operations to complete. This allows the cache to prepare receive buffers beforehand, reducing latency when data arrives and improving overall read throughput.
Data Source
AI summary
Systems and methods are disclosed for managing the number of affirmatively associated cache lines related to the different sets of a data cache unit. A tag look-up unit implements two thresholds, which may be configurable thresholds, to manage the number of cache lines related to a given set that store dirty data or are reserved for in-flight read requests. If the number of affirmatively associated cache lines in a given set is equal to a maximum threshold, the tag look-up unit stalls future requests that require an available cache line within that set to be affirmatively associated. To reduce the number of stalled requests, the tag look-up unit transmits a high priority clean notification to a frame buffer logic when the number of affirmatively associated cache lines in a given set approaches the maximum threshold. The frame buffer logic then processes requests associated with that set preemptively.