Banked Cache Atomic Operation Routing for X86 Processors
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Solution Overview
Problem
In highly-threaded x86 processors, misaligned atomic operations lead to reduced performance due to the need for additional steps and increased latency, as they require handling across multiple cache banks, which is inefficient compared to aligned operations.
Innovation Solution
A processor architecture with a banked cache system that determines whether atomic memory addresses are aligned, allowing aligned operations to be executed efficiently within the cache, while misaligned operations are handled within the processor, reducing the number of steps required for execution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If misaligned atomic operations are handled across multiple cache banks, then correctness is maintained, but execution latency increases and performance decreases
Solution Approach 1:
The patent segments the atomic operation handling by alignment status. Aligned atomic operations are directed to execute within the cache using a two-step process, while misaligned atomic operations are handled by the core using a four-step process. This segmentation allows the system to optimize for the common aligned case while still correctly handling misaligned cases.
Solution Approach 2:
The patent applies different execution qualities to different operation types. Aligned operations receive the optimized fast path execution in the cache, while misaligned operations receive the more complex but correct execution path in the core. This local quality differentiation resolves the contradiction by providing appropriate handling for each case.
2Productivity
If aligned atomic operations are executed in the cache with a two-step process, then execution efficiency is improved, but misaligned operations require a more complex four-step process
Solution Approach 1:
The patent implements dynamic operation routing based on alignment detection. The system dynamically determines whether an atomic operation is aligned or misaligned and directs it to the appropriate execution path. This dynamic approach allows the system to achieve high efficiency for aligned operations while maintaining correctness for misaligned operations.
Solution Approach 2:
The patent changes the execution parameters (number of steps, execution location) based on the alignment parameter of the atomic operation. By detecting the alignment parameter and adjusting the execution path accordingly, the system optimizes performance for aligned operations while ensuring correctness for misaligned operations.
Data Source
AI summary
A multithreaded processor with a banked cache is provided. The instruction set includes at least one atomic operation which is executed in the L2 cache if the atomic memory address source data is aligned. The core executing the instruction determines whether the atomic memory address source data is aligned. If it is aligned, the atomic memory address is sent to the bank that contains the atomic memory address source data, and the operation is executed in the bank. In one embodiment, if the instruction is mis-aligned, the operation is executed in the core.