Understanding the multi-queue block I/O framework

The organization of the storage hierarchy in Linux bears some resemblance to the network stack in Linux. Both are multi-layered and strictly define the role of each layer in the stack. Device drivers and physical interfaces are involved that dictate the overall performance. Similar to the behavior of the block layer, when a network packet was ready for transmission, it was placed in a single queue. This approach was used for several years until the network hardware evolved to support multiple queues. Hence, for devices with multiple queues, this approach became obsolete.

This problem was pretty similar to the one that was later faced by the block layer in the kernel. The network stack in the Linux kernel solved this problem a lot earlier than the storage stack. Hence, the kernel’s storage stack took a cue from this, which led to the creation of a new framework for the Linux block layer, known as the multi-queue block I/O queuing...