TLB Invalidation Synchronization via Consolidated Acknowledgements
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Solution Overview
Problem
In computing systems with multiple processing elements, synchronizing translation lookaside buffer (TLB) invalidations across processing elements is inefficient due to the large number of acknowledgement messages sent over the processor bus, which can consume excessive bandwidth.
Innovation Solution
A method where a first processing element issues a translation lookaside buffer invalidation instruction and sends it to a second processing element, with a broadcast element maintaining a count of invalidation instructions. After receiving a synchronization command, the second processing element sends a consolidated acknowledgement once all prior invalidation instructions are complete, reducing the number of acknowledgement messages by consolidating them at the broadcast element before sending to the first processing element.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If each processing element sends individual acknowledgement messages for every TLB invalidation instruction received, then reliability of synchronization is improved, but bandwidth consumption deteriorates
Solution Approach 1:
Multiple individual acknowledgement messages from different processing elements are merged into a single consolidated acknowledgement message at the broadcast element. This combining of multiple messages into one reduces the total number of messages on the bus while maintaining synchronization reliability, as the single message confirms that all processing elements have completed their TLB invalidation operations.
Solution Approach 2:
The broadcast element acts as an intermediary that receives individual acknowledgement messages from multiple processing elements, consolidates them, and then sends a single consolidated acknowledgement back to the originating processing element. This intermediary approach maintains the reliability of individual acknowledgements while reducing overall bandwidth consumption through message consolidation.
2Measurement precision
If multiple individual acknowledgement messages are sent for each TLB invalidation instruction, then synchronization accuracy is improved, but processing efficiency deteriorates
Solution Approach 1:
The patent merges multiple individual acknowledgement messages into a single consolidated acknowledgement message at the broadcast element. This consolidation maintains the accuracy of synchronization tracking while improving processing efficiency by reducing the total number of message transactions on the processor bus, thereby reducing overhead and freeing bandwidth for other operations.
3Reliability
If a large number of acknowledgement messages are transmitted over the processor bus, then completeness of synchronization confirmation is improved, but bandwidth availability deteriorates
Solution Approach 1:
The patent combines multiple individual acknowledgement messages from multiple processing elements into a single consolidated acknowledgement message. This merging approach ensures that synchronization completeness is maintained (as the consolidated message confirms all elements have completed their operations) while significantly improving bandwidth availability by reducing the total volume of traffic on the processor bus.
Solution Approach 2:
The broadcast element serves as an intermediary that collects individual acknowledgements from multiple processing elements, consolidates them into a single message, and transmits it back to the originating element. This intermediary function preserves the completeness of synchronization confirmation while conserving bandwidth by eliminating redundant message transmissions.
Data Source
AI summary
Each of multiple translation lookaside buffers (TLBs) is associated with a corresponding processing element. A first TLB invalidation (TLBI) instruction is issued at a first processing element, and sent to a second processing element. An element-specific synchronization instruction is issued at the first processing element. A synchronization command is broadcast, and received at the second processing element. The element-specific synchronization instruction prevents issuance of additional TLBI instructions at the first processing element until an acknowledgement in response to the synchronization command is received at the first processing element. After completion of any TLBI instructions issued at the second processing element before the synchronization command was received, the acknowledgement is sent from the second processing element to the first processing element, indicating that any TLBI instructions issued at the second processing element before the synchronization command was received at the second processing element are complete.