TLB Partitioning via Address Bit Segmentation
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Solution Overview
Problem
Conventional set associative translation lookaside buffers (TLBs) lack sufficient resolution to effectively partition resources among multiple agents, leading to thrashing and inefficient use of memory access resources.
Innovation Solution
A partitioning mechanism that assigns sub-components of address sets to different agents using target conversion logic, separating address bits into original tag bits, fixed set bits, and variable set bits, and calculates updated set and tag bits based on a client ID and programmable partition assignment table to dynamically allocate TLB resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a typical set associative TLB is used with a small number of ways, then the device complexity is reduced, but the partitioning resolution is insufficient to effectively partition TLB resources among multiple agents
Solution Approach 1:
The patent segments the TLB into multiple partitions by dynamically assigning subsets of sets to different agents based on client ID. Instead of having a fixed small number of ways, the TLB sets are divided and assigned to different agents (e.g., GPU, IOMMU, display controller) through a partitioning mechanism that uses address set bits and client identification to determine which agent accesses which partition, thereby achieving fine-grained partitioning resolution without increasing overall device complexity
Solution Approach 2:
The patent implements dynamic partitioning where the assignment of TLB sets to agents is not fixed but can be reconfigured. The partitioning mechanism dynamically determines which agent accesses which TLB partition based on the client ID and address set bits, allowing flexible resource allocation that adapts to different access patterns and workload requirements, thus improving partitioning resolution without requiring a statically complex structure
2Area of stationary object
If multiple agents share a common TLB, then the area efficiency is improved, but thrashing occurs between agents leading to degraded performance
Solution Approach 1:
The patent segments the shared TLB into multiple partitions that are dynamically assigned to different agents. Each agent receives a subset of TLB sets based on its client ID and the partitioning scheme, preventing thrashing by ensuring that each agent has dedicated access to its assigned partitions while still sharing the overall TLB structure, thus maintaining area efficiency while improving memory access performance
Solution Approach 2:
The patent introduces a partitioning mechanism that acts as an intermediary between multiple agents and the shared TLB. This mechanism uses address set bits and client ID to determine which agent should access which TLB partition, effectively mediating access conflicts and preventing thrashing while allowing multiple agents to share the TLB resource efficiently
3Productivity
If a TLB partitioning mechanism is implemented to prevent thrashing, then the memory access performance is improved, but the device complexity increases
Solution Approach 1:
The patent implements a self-service partitioning mechanism where the TLB automatically determines which agent should access which partition based on the client ID and address set bits embedded in the address translation requests. The partitioning logic is integrated into the TLB operation itself, allowing the system to self-manage partition assignments without requiring complex external control logic, thus improving memory access performance while minimizing the increase in device complexity
Data Source
AI summary
An apparatus to facilitate cache partitioning is disclosed. The apparatus includes a set associative cache to receive access requests from a plurality of agents and partitioning logic to partition the set associative cache by assigning sub-components of a set address to each of the plurality of agents.