在IBM Power8 +体系结构和FlashSystem 900上探索一致性加速器处理器接口（CAPI）的行为
Exploring the Behavior of Coherent Accelerator Processor Interface (CAPI) on IBM Power8+ Architecture and FlashSystem 900
摘要：
Coherent Accelerator Processor Interface（CAPI）是一个通用术语，用于表示为连接到IBM POWER 8+ System的闪存提供高吞吐量和低延迟路径的基础设施。CAPI加速卡作为对等体连贯地连接到Power8+处理器。这消除了IO子系统的开销和复杂性，并允许加速器作为应用程序的一部分进行操作。在本文中，我们提出了实验的结果，IBM FlashSystem 900（FS 900）与CAPI加速卡使用“CAPI-Flash IBM数据引擎NoSQL软件”库。此库提供应用程序，通过用户空间API对底层闪存存储进行直接存取，以管理和访问闪存中的数据。这将内核IO驱动程序功能卸载到专用CAPI FPGA加速器硬件。我们使用CAPI加速卡进行了实验，以分析FS 900的性能，使用关键值层API，采用NASA的MODIS陆地表面反射率数据集作为大型数据集用例。我们通过改变线程的数量，对大小从1 MB到3 TB的数据集执行读和写操作。然后，我们将此性能与其他异构存储和内存设备（如NVM，SSD和RAM）进行了比较，而无需在同步和异步文件IO操作模式下使用CAPI加速器。结果表明，FS 900和CAPI，加上RAM中的元数据缓存，提供了最高的IO/s和OP/s的读操作。这比仅仅使用RAM更高，同时使用更少的CPU资源。在FS 900、SSD和NVM中，FS 900具有最高的写入IO/s。另一个重要的观察结果是，当输入数据集的大小超过RAM的容量时，并且当数据访问不均匀和稀疏时，带有CAPI的FS 900将是一个具有成本效益的替代方案。
英文摘要：
The Coherent Accelerator Processor Interface (CAPI) is a general term for the infrastructure that provides high throughput and low latency path to the flash storage connected to the IBM POWER 8+ System. CAPI accelerator card is attached coherently as a peer to the Power8+ processor. This removes the overhead and complexity of the IO subsystem and allows the accelerator to operate as part of an application. In this paper, we present the results of experiments on IBM FlashSystem900 (FS900) with CAPI accelerator card using the "CAPI-Flash IBM Data Engine for NoSQL Software" Library. This library provides the application, a direct access to the underlying flash storage through user space APIs, to manage and access the data in flash. This offloads kernel IO driver functionality to dedicated CAPI FPGA accelerator hardware. We conducted experiments to analyze the performance of FS900 with CAPI accelerator card, using the Key Value Layer APIs, employing NASA's MODIS Land Surface Reflectance dataset as a large dataset use case. We performed Read and Write operations on datasets of size ranging from 1MB to 3TB by varying the number of threads. We then compared this performance with other heterogeneous storage and memory devices such as NVM, SSD and RAM, without using the CAPI Accelerator in synchronous and asynchronous file IO modes of operations. The results indicate that FS900 & CAPI, together with the metadata cache in RAM, delivers the highest IO/s and OP/s for read operations. This was higher than just using RAM, along with utilizing lesser CPU resources. Among FS900, SSD and NVM, FS900 had the highest write IO/s. Another important observation is that, when the size of the input dataset exceeds the capacity of RAM, and when the data access is non-uniform and sparse, FS900 with CAPI would be a cost-effective alternative.
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