HourGlass：一种可预测的基于时间的缓存一致性协议
HourGlass: Predictable Time-based Cache Coherence Protocol for Dual-Critical Multi-Core Systems
摘要：
我们提出了一种硬件机制，称为HourGlass可预见的多核系统中的核心被明确指定为关键或非关键的数据共享。HourGlass是用于双关键多核系统的基于时间的缓存一致性协议，其确保源自关键核的存储器请求的最坏情况延迟（WCL）界限。虽然HourGlass不为来自非关键核心的内存请求提供WCL或带宽保证，但它提倡使用计时器来提高其带宽利用率，同时仍然保持关键核心的WCL界限。这鼓励在关键核心的WCL界限和通过定时器配置为非关键核心改进的内存带宽之间进行权衡。我们使用gem 5评估HourGlass，并使用多线程基准套件（包括SPLASH-2）和合成工作负载。我们的结果表明，使用HourGlass的关键核心的WCL始终在分析WCL界限内，并且与最先进的实时缓存一致性协议相比，在关键核心上提供了更严格的WCL界限。此外，我们表明，HourGlass实现了关键核心的可证明的WCL界限之间的权衡，并提高了非关键核心的带宽利用率。HourGlass的平均性能与最先进的实时缓存一致性协议相当，与传统的MSI和MESI协议相比，其速度分别减慢了1.43倍和1.46倍。
英文摘要：
We present a hardware mechanism called HourGlass to predictably share data in a multi-core system where cores are explicitly designated as critical or non-critical. HourGlass is a time-based cache coherence protocol for dual-critical multi-core systems that ensures worst-case latency (WCL) bounds for memory requests originating from critical cores. Although HourGlass does not provide either WCL or bandwidth guarantees for memory requests from non-critical cores, it promotes the use of timers to improve its bandwidth utilization while still maintaining WCL bounds for critical cores. This encourages a trade-off between the WCL bounds for critical cores, and the improved memory bandwidth for non-critical cores via timer configurations. We evaluate HourGlass using gem5, and with multithreaded benchmark suites including SPLASH-2, and synthetic workloads. Our results show that the WCL for critical cores with HourGlass is always within the analytical WCL bounds, and provides a tighter WCL bound on critical cores compared to the state-of-the-art real-time cache coherence protocol. Further, we show that HourGlass enables a trade-off between provable WCL bounds for critical cores, and improved bandwidth utilization for non-critical cores. The average-case performance of HourGlass is comparable to the state-of-the-art real-time cache coherence protocol, and suffers a slowdown of 1.43x and 1.46x compared to the conventional MSI and MESI protocols.
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