Host-Assisted Row Hammer Mitigation via Dynamic Refresh Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As memory device geometries decrease, the row hammer effect becomes more prevalent, leading to data loss due to increased sensitivity of DRAM devices, where repeated access to one row can cause failures in adjacent rows, and traditional mitigation methods burden the memory controller and require inefficient increased refresh rates.
Innovation Solution
Implementing host-assisted row hammer mitigation, where the memory controller tracks activate commands and sends additional refresh cycles only when necessary, allowing the memory device to perform row hammer mitigation without compromising data integrity by refreshing potential victim rows, thus reducing the need for constant power and bandwidth usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the refresh rate is increased to provide more refresh cycles for row hammer mitigation, then the availability of refresh cycles for row hammer mitigation is improved, but the power consumption and bandwidth usage increase constantly even when row hammer conditions are not present
Solution Approach 1:
The refresh rate is made dynamic rather than static. The memory controller adjusts the refresh rate based on real-time monitoring of activate command frequencies. When row hammer conditions are detected (high activate frequency), the refresh rate increases to provide sufficient refresh cycles. When normal operation occurs, the refresh rate returns to standard levels, optimizing power efficiency while maintaining row hammer mitigation capability when needed.
Solution Approach 2:
The refresh rate parameter is changed dynamically based on operating conditions. The system monitors the frequency of activate commands and adjusts the refresh rate parameter accordingly. This allows the system to transition between different refresh rate states (standard vs. increased) based on whether row hammer conditions are present, resolving the contradiction between reliability and power consumption.
2Reliability
If the refresh rate is increased to provide more refresh cycles for row hammer mitigation, then the availability of refresh cycles for row hammer mitigation is improved, but the memory bus bandwidth consumption increases constantly even when row hammer conditions are not present
Solution Approach 1:
The refresh rate is made dynamic rather than static. The memory controller adjusts the refresh rate based on real-time monitoring of activate command frequencies. When row hammer conditions are detected (high activate frequency), the refresh rate increases to provide sufficient refresh cycles. When normal operation occurs, the refresh rate returns to standard levels, optimizing bandwidth efficiency while maintaining row hammer mitigation capability when needed.
Solution Approach 2:
The refresh rate parameter is changed dynamically based on operating conditions. The system monitors the frequency of activate commands and adjusts the refresh rate parameter accordingly. This allows the system to transition between different refresh rate states (standard vs. increased) based on whether row hammer conditions are present, resolving the contradiction between reliability and bandwidth consumption.
3Reliability
If traditional row hammer mitigation is implemented by the memory controller, then the row hammer mitigation capability is improved, but the burden on the memory controller and coordination complexity increases
Solution Approach 1:
The memory device performs self-service for row hammer mitigation by autonomously monitoring its own activate command frequencies and performing refresh operations when row hammer conditions are detected. This reduces the burden on the memory controller while maintaining effective row hammer mitigation. The memory device uses its internal resources to detect and mitigate row hammer events without requiring complex coordination with the controller.
Solution Approach 2:
The system implements feedback mechanisms where the memory device monitors its own operation patterns and adjusts its refresh behavior accordingly. When the memory device detects high activate frequencies indicating potential row hammer conditions, it automatically increases refresh cycles for affected rows. This feedback-driven approach enables autonomous row hammer mitigation without placing significant burden on the memory controller.
Data Source
AI summary
A memory device with internal row hammer mitigation couples to a memory controller. The memory controller or host can assist with row hammer mitigation by sending additional refresh cycles or refresh commands. In response to an extra refresh command the memory device can perform refresh for row hammer mitigation instead of refresh for standard data integrity. The memory controller can keep track of the number of activate commands sent to the memory device, and in response to a threshold number of activate commands, the memory controller sends the additional refresh command. With the extra refresh command the memory device can refresh the potential victim rows of a potential aggressor row, instead of simply refreshing a row that has not been accessed for a period of time.