L2 Cache Atomic Operation Pipelining via Reference Counters
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Efficient processing of atomic operations in a parallel processing architecture is complicated due to the need to maintain atomicity and distinguish between dependent and independent operations in the L2 cache, leading to stalled operations and reduced efficiency.
Innovation Solution
A method involving receiving atomic operations, determining cache line availability, incrementing a reference counter, and transmitting commands and data to an external arithmetic logic unit for processing, allowing pipelining of related atomic operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If atomic operations are processed in the L2 cache to maintain atomicity, then data consistency is ensured, but processing efficiency decreases due to stalled operations
Solution Approach 1:
The patent segments the atomic operation processing into two parts: the L2 cache handles address validation and cache line reservation, while the external ALU block performs the actual atomic computation. This segmentation allows the cache to prepare data structures in advance without waiting for the computationally intensive atomic operation to complete, thereby maintaining data consistency while improving processing throughput.
Solution Approach 2:
The patent implements preliminary action by having the L2 cache perform tag lookups and reserve cache lines before the atomic operation is executed by the external ALU. The reference counter is incremented in advance, and the cache line is marked as reserved, allowing subsequent dependent operations to be properly identified and stalled only when necessary, rather than preventing all processing upfront.
2Reliability
If the L2 cache reserves cache lines for atomic operations, then atomicity is maintained, but cache utilization decreases due to unavailable memory space
Solution Approach 1:
The patent introduces a reference counter as an intermediary mechanism between the cache line reservation and the actual atomic operation execution. The reference counter tracks how many atomic operations are waiting to use a particular cache line, allowing the cache to manage multiple pending operations efficiently. This intermediary enables fine-grained control over cache line availability, preventing unnecessary stalls while maintaining atomicity guarantees.
3Reliability
If dependent operations are stalled to maintain atomicity, then data consistency is ensured, but processing time increases
Solution Approach 1:
The patent implements feedback through the reference counter mechanism that continuously monitors the state of cache lines associated with atomic operations. When the reference counter reaches zero, indicating all atomic operations on a cache line are complete, the cache line is automatically freed for new operations. This feedback-driven approach ensures that operations are stalled only when absolutely necessary for atomicity, rather than maintaining prolonged stalls, thus minimizing processing time loss while ensuring data consistency.
Data Source
AI summary
One embodiment of the invention sets forth a mechanism for efficiently processing atomic operations transmitted from multiple general processing clusters to an L2 cache. A tag look-up unit tracks the availability of each cache line in the L2 cache, reserves the necessary cache lines for the atomic operations and transmits the atomic operations to an ALU for processing. The tag look-up unit also increments a reference counter associated with a reserved cache line each time an atomic operation associated with that cache line is received. This feature allows multiple atomic operations associated with the same cache line to be pipelined to the ALU. A ROP unit that includes the ALU may request additional data necessary to process an atomic operation from the L2 cache. Result data is stored in the L2 cache and may also be returned to the general processing clusters.