TLB Request Filter for Duplicate Virtual Address Elimination
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Solution Overview
Problem
The latency in processing requests to translation lookaside buffers (TLBs) leads to duplicate requests for the same page, unnecessarily consuming power and bandwidth, as the L1 TLB waits for acknowledgment from the L2 TLB, causing potential duplicate postings during the latency period.
Innovation Solution
Implementing a request filter that compares virtual addresses of subsequent misses to the L1 TLB with previous requests posted to the L2 TLB, filtering out duplicate requests by storing information on pending requests until acknowledgment is received from the L2 TLB, thereby preventing unnecessary postings to the L2 TLB.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the L1 TLB waits for acknowledgment from the L2 TLB, then the accuracy of address translation is improved, but the time delay increases and duplicate requests are generated
Solution Approach 1:
The filter is configured to identify and block duplicate requests before they reach the L2 TLB, based on virtual addresses of previous requests that are still pending acknowledgment. This preliminary filtering action prevents redundant requests from being generated during the latency period, resolving the contradiction by maintaining translation accuracy while eliminating time waste from duplicate requests.
2Device complexity
If duplicate requests are allowed to pass through, then the simplicity of the TLB system is maintained, but the power consumption increases
Solution Approach 1:
The filter extracts and removes duplicate requests from the request stream before they reach the L2 TLB. By taking out only the redundant requests while allowing unique requests to pass through, the system maintains its basic simplicity while significantly reducing power consumption from unnecessary processing and bandwidth usage.
3Reliability
If duplicate requests are posted to the L2 TLB, then the completeness of request processing is maintained, but the bandwidth consumption increases
Solution Approach 1:
The filter extracts and blocks duplicate requests from reaching the L2 TLB, allowing only necessary requests to be processed. This maintains request processing completeness for unique addresses while reducing bandwidth consumption by eliminating redundant transmissions to the L2 TLB.
Data Source
AI summary
The present application describes a method and apparatus for filtering requests to a translation lookaside buffer (TLB). Some embodiments of the method include receiving, from a first translation lookaside buffer (TLB), an indication of a first virtual address associated with a request to a second TLB for a page table entry in response to a miss in the first TLB. Some embodiments of the method also include filtering the request based on a comparison of the first virtual address and one or more second virtual addresses associated with one or more previous requests to the second TLB.