Remote Atomic Floating-Point Operations for Lower Latency
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Solution Overview
Problem
Existing multi-core processor systems face inefficiencies in executing atomic memory operations due to long latencies, cache line ping-ponging, coherence overhead, and serialization, leading to reduced throughput and increased latency, especially under contention among cores.
Innovation Solution
Implementing Remote Atomic Operations (RAO) instructions that allow atomic memory operations to be executed in various locations within the processor, including cores, private caches, shared caches, cache control circuits, memory controllers, or remote cores, with weakly ordered memory accesses to reduce latency and serialization, and optimize execution based on power, performance, and throughput.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If atomic memory operations are executed in traditional multi-core systems, then memory operations can be performed, but latency increases and throughput decreases due to cache line ping-ponging and coherence overhead
Solution Approach 1:
The patent segments the execution of atomic operations by allowing them to be performed at different locations in the memory hierarchy (L1 cache, L2 cache, or main memory) rather than forcing all operations through a single centralized location. This segmentation enables parallel execution paths and reduces serialization latency.
Solution Approach 2:
The patent introduces a new dimension to memory operation execution by enabling remote atomic operations across different memory levels and locations. Instead of traditional local operations only, the system allows atomic operations to span across cache levels and memory controllers, adding a spatial dimension to operation execution that reduces contention latency.
2Productivity
If multiple cores contend for the same cache line, then data sharing is achieved, but serialization occurs and throughput is limited to less than one operation every 100 clock cycles
Solution Approach 1:
The patent implements dynamic execution location selection for atomic operations. The system can dynamically determine whether to execute an operation locally or remotely based on current memory hierarchy state and contention conditions. This dynamic adaptation allows the system to optimize throughput by avoiding serialization when possible.
Solution Approach 2:
The patent introduces memory controllers and cache control circuits as intermediary elements that can execute atomic operations independently of core-level contention. These intermediaries act as buffers between contending cores, allowing operations to proceed in parallel without direct core-to-core serialization.
3Productivity
If atomic operations are executed at the core level, then operations are simple, but cache pressure increases and performance degrades under contention
Solution Approach 1:
The patent extracts atomic operation execution from the core level and distributes it to lower levels of the memory hierarchy (L1/L2 cache and memory controllers). By taking out operations from the core execution path, the system reduces cache pressure at critical locations and enables parallel processing of atomic operations.
Solution Approach 2:
The patent implements multiple copies of atomic operation execution capabilities at different memory hierarchy levels. Instead of a single execution path, the system maintains operational copies at core level, L1 cache level, L2 cache level, and memory controller level, allowing operations to be executed at the most appropriate location based on current conditions.
Data Source
AI summary
Embodiments relate to atomic memory operations with floating point values. An example processor comprises: a control register to store rounding mode and denormal mode control bits to indicate a rounding mode and denormal value processing mode; fetch circuitry to fetch a remote atomic operation (RAO) floating point (FP) instruction comprising a memory location to store at least one FP result value; decode circuitry to decode the instruction and scheduling circuitry to offload the instruction to an execution engine external to the logical processor or to schedule the decoded instruction for local execution, wherein an indication of the rounding mode and denormal value processing mode is communicated to the execution engine, the indication to be communicated by a transfer of one or more of the rounding mode control bits and denormal mode control bits to a storage coupled to the execution engine, or to be communicated in the message.