Cache Line Locking for Atomic Primitive Execution
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In multi-processor systems, the lack of atomicity in read-modify-write sequences can lead to unintended outcomes, such as memory locations being incremented only once instead of twice, due to concurrent access and modification by multiple processors.
Innovation Solution
Implementing atomic primitives using cache line locking, where the lock instruction prevents other processors from accessing the memory region until the operation is complete, ensuring that the execution of atomic primitives like increment, decrement, add, swap, test-and-set, compare-and-swap, and double compare-and-swap primitives is guaranteed to be atomic.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple processors concurrently access and modify the same memory location without atomic operations, then processing throughput is improved, but data integrity and reliability deteriorate
Solution Approach 1:
The patent introduces a lock instruction as an intermediary mechanism that mediates access to memory locations by multiple processors. The lock instruction acts as a mediator that coordinates concurrent access, ensuring that only one processor can modify a memory location at a time, thus maintaining data integrity while allowing multiple processors to operate concurrently.
Solution Approach 2:
The patent applies preliminary action by acquiring a lock on a memory location before performing any read-modify-write operations. The lock is obtained in advance, before the actual data modification occurs, ensuring that the subsequent operation will be atomic and that no other processor can interfere with the operation in progress.
2Reliability
If lock instructions are used to ensure atomicity of memory operations, then data integrity is improved, but processing speed and productivity worsen
Solution Approach 1:
The patent applies local quality by implementing fine-grained locking where each memory location has its own lock rather than using a global lock. This allows different memory locations to be accessed concurrently by different processors, reducing lock contention and improving processing speed while maintaining data integrity for each specific memory location.
3Productivity
If read-modify-write sequences are executed without atomic guarantees, then processing efficiency is improved, but correctness and manufacturing precision deteriorate
Solution Approach 1:
The patent uses preliminary action by acquiring the lock before executing the read-modify-write sequence. This preliminary lock acquisition guarantees that the subsequent read, modify, and write operations will execute atomically without interference from other processors, ensuring operation correctness while maintaining processing efficiency.
Data Source
AI summary
A processor comprising a cache, the cache comprising a cache line, an execution unit to execute an atomic primitive to responsive to executing a read instruction to retrieve a data item from a memory location, cause to store a copy of the data item in the cache line, execute a lock instruction to lock the cache line to the processor, execute at least one instruction while the cache line is locked to the processor, and execute an unlock instruction to cause the cache controller to release the cache line from the processor.