IOMMU Rate Limiting for Device Utilization Management
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Solution Overview
Problem
In data centers, processes that exceed their Service Level Agreement (SLA) parameters for device bandwidth usage can hinder other processes, leading to inefficient resource allocation and potential device stalling.
Innovation Solution
Implementing Input-Output Memory Management Unit (IOMMU) processor rate limiting for Address Translation Services (ATS) to enforce SLA compliance, thereby limiting excessive device utilization across various devices such as network interface controllers, accelerators, and GPUs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a process requests device utilization in excess of its SLA, then the process can perform operations faster, but it prevents usage of the device by other processes
Solution Approach 1:
The patent introduces an IOMMU (Input-Output Memory Management Unit) as an intermediary between the process and the device. The IOMMU intercepts address translation requests from the device, checks whether the process has sufficient tokens to cover the requested operations, and either permits or blocks the translation based on token availability. This mediator enforces SLA compliance by limiting device access to processes that have not exceeded their allocated bandwidth, while still allowing compliant processes to utilize the device at full speed.
2Productivity
If device bandwidth is unlimited for one process, then that process achieves maximum performance, but other processes experience device stalling
Solution Approach 1:
The system implements a feedback mechanism where the IOMMU continuously monitors token consumption by processes and dynamically adjusts device access permissions accordingly. When a process consumes tokens through device operations, the IOMMU tracks this consumption and prevents further access once the token balance would go negative. This feedback loop ensures that no single process can monopolize the device, preventing stalling for other processes while maintaining maximum performance for compliant processes.
3Adaptability or versatility
If SLA enforcement is implemented at process level, then resource allocation becomes fair, but system complexity increases
Solution Approach 1:
The patent leverages the existing IOMMU architecture, which is already present in modern systems for address translation purposes. Rather than building a completely new enforcement mechanism, the invention copies and extends the existing IOMMU functionality to include token-based access control. The IOMMU's existing translation request handling infrastructure is reused, and token checking is integrated into this existing flow, thereby achieving fair resource allocation without proportionally increasing system complexity.
Data Source
AI summary
Examples described herein relate to a device that includes a host interface; circuitry coupled to the host interface; and second circuitry. The second circuitry is to limit usage of the circuitry, by a first process, by limiting performance of requests for translation of virtual memory addresses to physical memory addresses, from the first process. The circuitry includes one or more of: a network interface device, an accelerator, memory, or storage.