Memory Page Access Tracking With Probabilistic Counter Updates
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Solution Overview
Problem
Existing methods for tracking memory page access frequencies are costly in terms of performance, memory overhead, and circuit area, especially when distinguishing between pages accessed a very large number of times and those accessed a smaller number of times.
Innovation Solution
Implement a chance-dependent test to update access frequency tracking indicators only some of the time, using a probabilistic approach to reduce circuit area, power, and performance costs, allowing for tracking a wide range of access frequencies with a smaller counter or indicator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If counters with sufficient number of bits are used to track access frequency over a large range, then measurement precision is improved, but device complexity and circuit area increase
Solution Approach 1:
The patent applies partial action by updating the access frequency counter only some of the time rather than on every access. A chance-dependent test determines whether to update the counter, allowing the system to track access frequency trends without maintaining precise counts for every access, thus reducing counter complexity while maintaining sufficient tracking precision
Solution Approach 2:
The patent changes the parameter of update frequency from deterministic (every access) to probabilistic (chance-dependent). This parameter change allows the counter to be updated at a reduced rate while still providing meaningful access frequency information, reducing the required counter precision and complexity
2Measurement precision
If counters with sufficient number of bits are used to track access frequency over a large range, then measurement precision is improved, but circuit area increases
Solution Approach 1:
By updating the counter only partially (some of the time) rather than on every access, the patent reduces the maximum count value the counter must accommodate. This reduces the number of bits required and thus the circuit area, while still providing sufficient precision for determining frequently accessed pages
Solution Approach 2:
The patent uses a simple chance-dependent test mechanism that requires minimal circuit resources. Rather than investing in a large, complex counter, the system uses a lightweight probabilistic update mechanism that achieves the same functional goal with much less circuit area
3Measurement precision
If access frequency tracking is performed on every memory access, then measurement precision is improved, but productivity decreases due to performance overhead
Solution Approach 1:
The patent performs access frequency tracking partially rather than completely - the counter is updated only when the chance-dependent test succeeds. This reduces the performance overhead associated with tracking while still gathering sufficient information to identify frequently accessed pages for memory optimization
Solution Approach 2:
The chance-dependent test allows the system to skip counter updates for many accesses, rushing through them without the overhead of updating tracking structures. This maintains productivity by allowing most accesses to proceed quickly while still capturing frequency information for optimization purposes
4Measurement precision
If access frequency tracking is performed on every memory access, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent reduces power consumption by performing access frequency tracking partially - the counter is updated only when the chance-dependent test succeeds. This reduces the energy required for tracking operations while maintaining sufficient precision to identify frequently accessed pages for memory optimization
Solution Approach 2:
The chance-dependent test creates a periodic-like update pattern where counter updates occur at intervals rather than continuously. This reduces the average power consumption of the tracking circuitry while still accumulating meaningful frequency information over time
Data Source
AI summary
An apparatus comprises: memory access circuitry (11) to process memory access requests requesting access to a memory system (10, 32); and access frequency tracking circuitry (40). In response to a given memory access request requesting access to a given page of a memory address space, the access frequency tracking circuitry (40) determines an outcome of a chance-dependent test, where the outcome of the chance-dependent test is dependent on chance. When the outcome of the chance-dependent test is a first outcome, an access frequency tracking indicator corresponding to the given page is updated within an access frequency tracking structure. When the chance-dependent test has an outcome other than the first outcome, the access frequency tracking circuitry 40 omits updating of the access frequency tracking indicator corresponding to the given page.