Remote Atomic Operations for Multi-Core Latency
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Solution Overview
Problem
Existing atomic memory operations in multi-core systems face inefficiencies due to high latency, cache line ping-ponging, and coherence overhead, leading to poor performance and increased interconnect traffic, especially under contention among cores.
Innovation Solution
The implementation of Remote Atomic Operations (RAO) instructions that allow for atomic memory operations to be executed with reduced latency and serialization by queuing operations at a single location and performing them in place, using weakly-ordered memory semantics to hide latency and avoid traditional data hazards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional atomic memory operations are used in multi-core systems, then thread safety and data consistency are ensured, but latency increases and throughput decreases due to cache line ping-ponging and coherence overhead
Solution Approach 1:
The patent extracts the atomic operation execution from the traditional cache coherence protocol path. By introducing a separate fast path for atomic operations that bypasses the normal cache line invalidation and ping-ponging mechanisms, the system maintains thread safety while reducing latency. The atomic operations are handled through a dedicated mechanism that prevents cache line ping-ponging between cores.
Solution Approach 2:
The patent introduces an intermediary mechanism (atomic operation handling logic) that mediates between multiple cores accessing shared memory. This intermediary prevents direct cache line ping-ponging by coordinating atomic operations in a way that maintains consistency without requiring continuous cache coherence protocol intervention, thereby reducing both latency and interconnect traffic.
2Reliability
If traditional atomic memory operations are used, then data consistency is maintained, but interconnect network traffic increases due to cache line ping-ponging among cores
Solution Approach 1:
The patent extracts atomic operation traffic from the general cache coherence interconnect path. By implementing a dedicated fast path for atomic operations, the system separates atomic operation traffic from normal memory traffic, reducing interconnect network congestion and energy consumption while maintaining data consistency through the specialized atomic operation handling mechanism.
3Reliability
If atomic operations are serialized to ensure correctness, then thread safety is maintained, but productivity decreases due to waiting threads
Solution Approach 1:
The patent implements preliminary action by pre-establishing atomic operation queues and validation mechanisms before actual atomic operations occur. This allows the system to prepare and batch atomic operations, reducing serialization overhead and improving throughput while maintaining thread safety through pre-configured consistency protocols.
Solution Approach 2:
The patent enables continuous atomic operation processing through a streamlined fast path that eliminates idle waiting periods. By maintaining continuous operation flow through dedicated atomic operation handling logic and reducing cache coherence interruptions, the system improves productivity while preserving thread safety through uninterrupted consistent state transitions.
Data Source
AI summary
Disclosed embodiments relate to atomic memory operations. In one example, a method of executing an instruction atomically and with weak order includes: fetching, by fetch circuitry, the instruction from code storage, the instruction including an opcode, a source identifier, and a destination identifier, decoding, by decode circuitry, the fetched instruction, selecting, by a scheduling circuit, an execution circuit among multiple circuits in a system, scheduling, by the scheduling circuit, execution of the decoded instruction out of order with respect to other instructions, with an order selected to optimize at least one of latency, throughput, power, and performance, and executing the decoded instruction, by the execution circuit, to: atomically read a datum from a location identified by the destination identifier, perform an operation on the datum as specified by the opcode, the operation to use a source operand identified by the source identifier, and write a result back to the location.