Memory Hierarchy Write Termination via Store Transient
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Solution Overview
Problem
High-performance microprocessors continue to complete memory write operations even after the data is no longer needed, wasting resources and energy due to the lack of awareness about the data's obsolescence in the memory hierarchy.
Innovation Solution
Incorporating commands like storetransient and loadlast into the instruction set architecture to initiate and interrupt write operations in a memory hierarchy, allowing the processing device to defer or terminate data propagation when data is no longer needed, thereby optimizing resource usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the microprocessor completes all memory write operations in the memory hierarchy, then data consistency is maintained, but energy is wasted on operations after data is no longer needed
Solution Approach 1:
The patent introduces a new store instruction that performs preliminary actions by only writing data to the first level of the memory hierarchy (register file or cache) without propagating to lower levels. This preliminary write operation allows the processor to indicate early that data is no longer needed, preventing unnecessary energy consumption in lower memory levels while maintaining data consistency for operations that do require propagation.
2Productivity
If the microprocessor propagates data through the entire memory hierarchy, then memory consistency is ensured, but resource usage increases unnecessarily
Solution Approach 1:
The patent segments the memory write operation into two distinct types: full propagation writes that traverse the entire memory hierarchy, and truncated writes that stop at the first level. This segmentation allows the system to choose the appropriate write type based on whether lower memory levels need the data, improving overall memory hierarchy efficiency by eliminating unnecessary propagation operations.
Solution Approach 2:
The patent implements partial action by allowing store instructions to perform only the necessary portion of the write operation - writing to the first level without excessive propagation to lower levels when the data is immediately needed. This partial write approach reduces resource consumption while maintaining adequate functionality for operations that require fast access.
3Reliability
If the microprocessor drains write buffers and completes coherency operations, then memory coherence is maintained, but execution time increases due to unnecessary operations
Solution Approach 1:
The new store instruction performs a preliminary write to the first memory level and immediately retires without waiting for coherency operations or buffer draining. This preliminary action allows the processor to continue execution without stalling, while still maintaining memory coherence for operations that require it, thereby reducing execution time penalties.
4Reliability
If the microprocessor completes all store operations, then data integrity is guaranteed, but energy is wasted on operations that serve no value to software
Solution Approach 1:
The patent segments store operations into two categories: those that require full propagation for data integrity (traditional stores) and those that only need first-level writing (new truncated stores). This segmentation allows the compiler or programmer to select the appropriate operation type based on whether lower memory levels need the data, eliminating energy waste while preserving data integrity when required.
Solution Approach 2:
The patent changes the parameter of write propagation distance by introducing a new store instruction with a different propagation parameter - writing only to the first level instead of propagating through all levels. This parameter change allows the system to adjust the scope of the write operation to match the actual need, reducing energy waste on unnecessary propagation while maintaining data integrity for operations that require it.
Data Source
AI summary
Systems, methods, and other embodiments associated with providing limited writing in a memory hierarchy are described. According to one embodiment, an apparatus includes a plurality of memory devices sequentially configured in a memory hierarchy. The apparatus also includes a first logic configured to execute a first command to initiate a sequence of write operations to write data to the plurality of memory devices in the memory hierarchy via propagation of the data sequentially through the memory hierarchy. The apparatus further includes a second logic configured to execute a second command to initiate an interruption of the sequence of write operations by indicating to at least one memory device of the plurality of memory devices to terminate the propagation of the data through the memory hierarchy prior to completing the propagation.