Adaptive Spinlock Prearbitration for Multiprocessor Contention
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Solution Overview
Problem
In multiprocessor systems, the contention for shared resources like spinlocks leads to cache misses and bus contention, resulting in performance slowdowns, especially under high contention scenarios, where the overhead of synchronization and access coordination increases, causing significant reductions in system efficiency and throughput.
Innovation Solution
The implementation of a timed prearbitration mechanism in the ticket-serving algorithm for spinlocks, which introduces a configurable wait quantum that adapts based on the processor's position in the queue, allowing processors to delay before actively spinning on the lock, thereby reducing cache misses and bus contention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If processors actively spin on the lock immediately when contending for a shared resource, then the latency to acquire the lock is reduced, but cache misses and bus contention increase significantly
Solution Approach 1:
The patent applies preliminary action by having processors determine their queue position and calculate an optimal wait time before actively spinning on the lock. This pre-computation allows processors to delay their spin attempt strategically, reducing immediate cache misses and bus contention while still acquiring the lock with minimal overall latency.
Solution Approach 2:
The patent implements dynamics by making the spin wait time adaptive rather than fixed. Processors dynamically adjust their wait behavior based on their position in the arbitration queue, with processors further back in the queue waiting longer before spinning. This dynamic approach optimizes the balance between lock acquisition speed and system-wide bus utilization.
2Object-generated harmful factors
If processors wait longer before spinning on the lock, then cache misses and bus contention are reduced, but the latency to acquire the lock increases
Solution Approach 1:
The patent applies parameter changes by modifying the wait time parameter based on the processor's queue position. Instead of a uniform wait strategy, each processor calculates its optimal wait time as a function of its position in the arbitration queue. This parameter adjustment allows the system to reduce bus contention without significantly increasing overall lock acquisition latency.
3Device complexity
If the ticket-serving algorithm uses a simple first-come-first-served approach, then the algorithm complexity is low, but performance degrades under high contention scenarios
Solution Approach 1:
The patent enhances the simple ticket-serving algorithm by adding preliminary action: processors determine their queue position when receiving the ticket and pre-calculate their optimal spin wait time based on this position. This extension maintains the simplicity of the core ticket algorithm while adding performance optimization that significantly improves throughput under high contention without requiring complex data structures or synchronization mechanisms.
Data Source
AI summary
A processor of an apparatus in an example upon a failure of an earlier attempt to directly acquire ownership of an access coordinator for a resource shared with one or more additional processors, locally determines an amount to delay a later attempt to directly acquire ownership of the access coordinator. Upon a failure of the later and/or a subsequent attempt to directly acquire ownership of the access coordinator the processor would enter into an indirect waiting arrangement for ownership of the access coordinator.