Coherent IO Device Bypassing PCI Ordering Rules
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Solution Overview
Problem
Existing computer systems face inefficiencies in information transfer and consistency maintenance across elements, particularly due to restrictive ordering rules in IO interfaces, which hinder performance and latency in data exchange between CPUs and IO devices.
Innovation Solution
The implementation of coherent IO devices directly connected to a coherent system interconnect, allowing for efficient data transfer within the CPU/memory domain using coherent transactions and a producer-consumer model, bypassing traditional PCI ordering rules and enabling cache coherence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional PCI ordering rules are used for IO device communication, then device compatibility and standardized operation are maintained, but data transfer latency increases and performance deteriorates
Solution Approach 1:
The patent introduces a translation layer or adapter that mediates between the coherent domain transactions and the PCI ordering rules. This intermediary component allows IO devices to communicate through the coherent interconnect while maintaining compatibility with traditional PCI protocols, thereby reducing latency without sacrificing device compatibility.
Solution Approach 2:
The patent changes the communication parameters by allowing IO devices to operate under different ordering rules when accessed through the coherent domain compared to traditional PCI access. This parameter change enables faster data transfer by bypassing restrictive PCI ordering constraints while maintaining backward compatibility through selective application of ordering rules.
2Adaptability or versatility
If IO devices are accessed through the IO domain with PCI ordering rules, then standardized IO operations are maintained, but throughput and scalability are limited
Solution Approach 1:
The patent implements a dynamic access mechanism where IO devices can be accessed through different domains (coherent or IO domain) depending on the specific operation requirements. This dynamic approach allows the system to switch between standardized PCI access for compatibility and high-performance coherent access for throughput-critical operations, thereby improving overall productivity while maintaining adaptability.
3Productivity
If coherent transactions are used for direct processor management of IO resources, then data transfer performance and scalability are improved, but complexity of maintaining cache coherence increases
Solution Approach 1:
The patent implements self-service mechanisms where the coherent IO devices automatically participate in cache coherence protocols and manage their own coherence state. This self-service approach reduces the burden on the processor and system software for maintaining cache coherence, thereby improving data transfer performance without proportionally increasing system complexity.
4Stability of the object's composition
If restrictive PCI ordering rules are applied to IO interfaces, then memory consistency is maintained, but flexibility in data access and processing efficiency are reduced
Solution Approach 1:
The patent segments the memory access space into coherent domain and IO domain, allowing different ordering rules to apply to different segments. This segmentation enables memory consistency to be maintained in the coherent domain through relaxed ordering rules while still providing flexibility for specific IO operations that require traditional PCI ordering, thereby resolving the contradiction between consistency and flexibility.
Data Source
AI summary
According to some embodiments, data to be exchanged via a system input output interface may be determined at a processor. It may then be arranged to exchange the data via a coherent input output device coupled to a coherent system interconnect. Other embodiments are described.