Compressed Tag Coherency Messaging in Packetized Networks
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Solution Overview
Problem
Cache-coherent packetized network systems face inefficiencies due to the large number of bits required to communicate coherent messages, leading to increased latency and reduced performance, especially in systems with compound coherency operations that require multiple parent-child reattachment tags.
Innovation Solution
Implementing a compressed tag mechanism that generates unique tags using a common compression function, allowing agents to bind child messages to their parent requests efficiently, reducing the need for extensive address or transaction ID tags and minimizing packet size.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the number of bits required to communicate coherent messages is reduced, then latency is reduced and bandwidth efficiency is improved, but the ability to correctly bind child messages to parent requests may be compromised
Solution Approach 1:
The patent extracts only the essential binding information (compressed tags) from the full address and transaction ID, removing redundant bits while preserving the critical function of message binding. This allows reduced message size without compromising reliability.
Solution Approach 2:
The patent creates a composite tagging mechanism that combines compressed address information with compressed transaction ID information into a unified tag structure. This composite approach maintains binding correctness while minimizing total bit requirements.
2Productivity
If the packet size is minimized, then transport efficiency is improved and latency is reduced, but the amount of information available for message binding is reduced
Solution Approach 1:
The patent changes the parameter representation from full-width addresses and transaction IDs to compressed tag forms. This parameter transformation reduces information size while maintaining the essential binding capability through clever encoding of the most significant bits.
3Duration of action of moving object
If the number of packet flits is reduced, then the latency of communicating messages is reduced, but the capability to support multiple simultaneous coherent agents is compromised
Solution Approach 1:
The compressed tag mechanism serves multiple functions simultaneously: it provides message binding, it enables multi-agent support, and it reduces latency. The universal tag structure can identify and bind messages from any number of coherent agents without requiring agent-specific overhead.
Data Source
AI summary
An example cache-coherent packetized network system includes: a home agent; a snooped agent; and a request agent configured to send, to the home agent, a request message for a first address, the request message having a first transaction identifier of the request agent; where the home agent is configured to send, to the snooped agent, a snoop request message for the first address, the snoop request message having a second transaction identifier of the home agent; and where the snooped agent is configured to send a data message to the request agent, the data message including a first compressed tag generated using a function based on the first address.