MMU Store Ordering With Selective Strong-Order Delays
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Solution Overview
Problem
Memory synchronization operations in modern computing systems, particularly in multiprocessor environments, consume significant processing time and resources, leading to performance bottlenecks due to the need for ensuring memory operation ordering across threads.
Innovation Solution
Implement a method where ordered store operations are delayed until an acknowledgement is received that a subsequent store operation is visible in memory, allowing processors to continue executing while pending operations are resolved, and utilize a memory management unit (MMU) to enforce ordering through weak and strong ordered store operations without additional software synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If memory synchronization operations are performed to ensure ordering of store operations, then ordering reliability is improved, but processing time increases significantly
Solution Approach 1:
The patent segments store operations into two types: ordered store operations and unordered store operations. Ordered store operations maintain strict ordering guarantees, while unordered store operations forgo ordering to achieve higher performance. This segmentation allows the system to apply ordering mechanisms only where necessary, reducing overall synchronization overhead and processing time while maintaining reliability for critical operations.
Solution Approach 2:
The patent changes the ordering parameter of store operations dynamically. By allowing store operations to be configured as either ordered or unordered, the system can adjust the ordering parameter based on specific requirements. Ordered operations use full synchronization mechanisms to ensure reliability, while unordered operations use simplified paths that reduce processing time, thus resolving the contradiction between reliability and time loss.
2Reliability
If multiple memory synchronization operations are serialized to guarantee visibility, then ordering reliability is improved, but processor performance decreases
Solution Approach 1:
The patent segments memory operations into ordered and unordered categories, allowing the system to process unordered operations without serialization. This segmentation enables parallel processing of multiple unordered store operations, maintaining visibility guarantees where needed while avoiding unnecessary serialization overhead, thus improving processor performance without sacrificing reliability for ordered operations.
Solution Approach 2:
The patent applies partial synchronization only to ordered store operations that require visibility guarantees, rather than serializing all memory operations. By applying synchronization selectively and partially, the system maintains reliability for critical ordered operations while allowing unordered operations to proceed in parallel, thereby improving overall processor performance without compromising necessary visibility guarantees.
3Reliability
If the thread is blocked during memory synchronization operations, then ordering reliability is improved, but productivity of the thread decreases
Solution Approach 1:
The patent segments threads into those executing ordered store operations and those executing unordered store operations. Threads executing unordered operations are not blocked during memory synchronization, as these operations do not require strict ordering guarantees. This segmentation allows threads to remain productive and continue executing other operations while unordered store operations are processed, improving thread productivity while maintaining synchronization reliability for ordered operations where blocking is still applied.
Data Source
AI summary
Various embodiments include techniques for performing memory store operations in a computing system. A memory management unit (MMU) receives various types of store operations from a processor, including unordered store operations, weak ordered store operations, and strong ordered store operations. The MMU performs virtual address to physical address translations for the store operations and forwards the translated store operations for execution. The MMU can perform translations for and forward unordered store operations and weak ordered store operations at any time. By contrast, the MMU can delay translations for and forwarding of strong ordered store operations while any prior ordered store operations are pending. In this manner, the MMU can enforce ordering of weak ordered store operations to be translated and executed prior to a subsequent strong ordered store operation. These techniques allow the processor to continue to perform other operations while ordered store operations are pending in the MMU.