Traditional buffered read for block devices is no longer effective in terms of latency with today's low-latency solid-state drives. This is because memory copy accounts for a large portion of I/O latency. Zero-copy read is an attractive approach to reducing the I/O latency, but has the inability to utilizing the page cache, thereby losing the opportunity to access reused data in DRAM-like speed. This study proposes an I/O stack that has the advantages of both zero-copy and the use of the page cache for modern low-latency SSD. In the proposed I/O stack, the page cache serves the read request by the application first. Upon a miss, the storage device transfers data to a user buffer directly. In the meantime, our scheme collects necessary information that is used later for prefetching data into the page cache in the background. Therefore, when an application accesses the data again, it can be served at DRAM-like speed. Our prototype in the Linux kernel shows up to 11 percent throughput improvement on the YCSB workload against the database applications.

中文翻译：

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零拷贝I / O堆栈，适用于低延迟SSD

就当今的低延迟固态硬盘而言，传统的块设备缓冲读取在延迟方面已不再有效。这是因为内存复制占了I / O延迟的很大一部分。零复制读取是减少I / O延迟的一种有吸引力的方法，但是无法利用页面缓存，从而失去了以类似DRAM的速度访问重用数据的机会。这项研究提出了一种I / O堆栈，该堆栈既具有零复制的优势，又具有针对现代低延迟SSD的页面缓存的使用。在建议的I / O堆栈中，页面缓存首先服务于应用程序的读取请求。如果未命中，则存储设备将数据直接传输到用户缓冲区。同时，我们的方案收集了必要的信息，这些信息稍后用于将数据预取到后台的页面缓存中。所以，当应用程序再次访问数据时，可以以类似DRAM的速度提供服务。我们在Linux内核中的原型将YCSB工作负载相对于数据库应用程序的吞吐量提高了11％。