Adaptive Remote Atomic Operations for Multi-Core Latency
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Solution Overview
Problem
Existing technologies face inefficiencies and high latency in executing atomic operations in multi-core systems, particularly due to cache line ping-ponging and coherence overhead, which limits throughput and increases latency.
Innovation Solution
The implementation of instructions for Remote Atomic Operations (RAO) that allow for efficient execution of atomic memory operations by queuing operations at a single location and performing them in place, while also enabling weakly ordered memory accesses to improve performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional atomic operations are executed in multi-core systems, then memory operations can be performed atomically, but cache line ping-ponging occurs and coherence overhead increases latency
Solution Approach 1:
The patent introduces a remote atomic operation unit as an intermediary component that handles atomic operations outside the traditional cache coherence path. This mediator receives atomic operation requests, performs them remotely without requiring cache line validation and eviction cycles, and returns results, thereby eliminating the ping-pong effect while maintaining atomicity guarantees
Solution Approach 2:
The patent extracts the atomic operation functionality from the traditional cache coherence protocol path. By separating atomic operations from the standard read-modify-write path that involves cache lines, the system removes the source of ping-ponging and coherence overhead, allowing atomic operations to execute through a dedicated remote path that does not interfere with normal cache operations
2Reliability
If traditional atomic operations are executed in multi-core systems, then memory operations can be performed atomically, but cache line ping-ponging increases interconnect network traffic
Solution Approach 1:
The remote atomic operation unit acts as an intermediary that intercepts atomic operation requests before they enter the interconnect network. By handling these operations locally through a dedicated path, the system prevents the generation of excessive network traffic that would otherwise result from cache line validation, eviction, and re-invalidation messages traversing the interconnect
Solution Approach 2:
The patent extracts atomic operation traffic from the general interconnect network path. By creating a separate remote execution path, the system removes the harmful network traffic generation associated with traditional atomic operations, allowing the interconnect to handle only necessary cache coherence traffic while atomic operations proceed through the isolated remote path
3Reliability
If traditional atomic operations are executed with high contention, then memory operations can be performed atomically, but throughput is limited to less than one operation per 100 clock cycles
Solution Approach 1:
The remote atomic operation unit serves as a specialized intermediary that processes atomic operations in parallel without being constrained by cache coherence limitations. This mediator can handle multiple atomic operations simultaneously through independent execution paths, breaking the serialization bottleneck that limits traditional systems to less than one operation per 100 clock cycles under contention
Solution Approach 2:
The patent segments the atomic operation processing into independent parallel paths through the remote execution unit. By dividing the monolithic cache coherence path into separate remote execution channels, the system enables multiple atomic operations to proceed simultaneously without interfering with each other, dramatically increasing throughput under contended conditions
Data Source
AI summary
Disclosed embodiments relate to atomic memory operations. In one example, an apparatus includes multiple processor cores, a cache hierarchy, a local execution unit, and a remote execution unit, and an adaptive remote atomic operation unit. The cache hierarchy includes a local cache at a first level and a shared cache at a second level. The local execution unit is to perform an atomic operation at the first level if the local cache is a storing a cache line including data for the atomic operation. The remote execution unit is to perform the atomic operation at the second level. The adaptive remote atomic operation unit is to determine whether to perform the first atomic operation at the first level or at the second level and whether to copy the cache line from the shared cache to the local cache.