SNC Memory Allocation via Policy Hints
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Solution Overview
Problem
In sub-NUMA clustering systems, the default memory allocation policy leads to uneven distribution of data across clusters, resulting in inefficiencies such as higher cache miss rates and increased access latency due to traffic congestion.
Innovation Solution
The implementation of specific SNC-policy-hint instructions, such as MOVSNCSHARE, VMOVSNCSHARE, and TMOVSNCSHARE, which guide hardware to interleave memory spaces across all clusters at page or block granularity, overriding the default first-touch policy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the default first-touch memory allocation policy is used in sub-NUMA cluster systems, then memory allocation is simple to implement, but data distribution becomes uneven across clusters leading to higher cache miss rates and increased access latency
Solution Approach 1:
The patent changes the memory allocation parameter from simple first-touch policy to an enhanced policy that considers SNC domain information. The circuitry determines whether to allocate memory to local or remote NUMA nodes based on the SNC domain of the requesting core, fundamentally changing how memory allocation decisions are made to achieve more balanced data distribution across clusters
Solution Approach 2:
The system incorporates feedback mechanisms where the circuitry continuously monitors data access patterns and dynamically adjusts memory allocation decisions. By tracking which cores access which data and their respective SNC domains, the system adapts its allocation strategy to maintain optimal data distribution and minimize cache misses under varying workload conditions
2Use of energy by moving object
If memory is allocated using default first-touch policy, then allocation overhead is low, but traffic congestion occurs leading to increased access latency
Solution Approach 1:
The patent applies preliminary action by pre-determining memory allocation based on SNC domain information before actual data access occurs. The circuitry proactively allocates memory to appropriate NUMA nodes based on predicted access patterns from SNC domain analysis, preventing traffic congestion before it happens and reducing access latency without significant overhead
Solution Approach 2:
The system implements local quality by tailoring memory allocation strategies to specific SNC domains. Each SNC domain receives customized allocation treatment based on its local memory controllers and cache hierarchy, optimizing access patterns for local cores while balancing overall system traffic to prevent congestion and reduce latency
3Device complexity
If data is concentrated in single NUMA node, then allocation is straightforward, but cache miss rate increases due to uneven distribution
Solution Approach 1:
The patent segments the memory allocation process into distinct decision stages: determining the requesting core's SNC domain, identifying appropriate target NUMA nodes, and allocating memory accordingly. This segmentation of the allocation process enables more sophisticated data distribution across multiple NUMA nodes while maintaining manageable complexity through structured decision-making
Solution Approach 2:
The system adds another dimension to memory allocation by incorporating SNC domain information into the allocation decision process. Instead of simple first-touch allocation, the circuitry considers the multi-dimensional relationship between cores, their SNC domains, and NUMA nodes, creating a more nuanced allocation strategy that improves cache hit rates through better data distribution
Data Source
AI summary
An embodiment of an integrated circuit may comprise circuitry communicatively coupled to two or more sub-non-uniform memory access clusters (SNCs) to allocate a specified memory space in the two or more SNCs in accordance with a SNC memory allocation policy indicated from a request to initialize the specified memory space. An embodiment of an apparatus may comprise decode circuitry to decode a single instruction, the single instruction to include a field for an opcode, and execution circuitry to execute the decoded instruction according to the opcode to provide an indicated SNC memory allocation policy (e.g., a SNC policy hint). Other embodiments are disclosed and claimed.