从iostat手册页：
rrqm/s
The number of read requests merged per second that were queued to the device.
wrqm/s
The number of write requests merged per second that were queued to the device.
r/s
The number (after merges) of read requests completed per second for the device.
w/s
The number (after merges) of write requests completed per second for the device.
merge由于文档没有提供任何进一步的细节，任何人都可以详细说明这个概念吗？
当两个 i/o 请求可以合并为一个较长的请求时，就会发生合并。例如，对块1234的写入随后对块1235的写入可以合并成对长度为2块的块1234的单个i/o请求。由于这种情况相当普遍，因此值得将精力放在内核中进行合并，释放 i/o 请求结构并减少中断开销。
如果您对有关 i/o 这方面的更详细统计信息感兴趣，请参阅 pdf btt 用户指南，该指南是
blktrace.