The IO Subsystem

An application cannot write directly to the devices, or to the network. It needs to channel the requests via the kernel. Similarly when an application wants to read some data, it performs a read system call. The kernel would load the data into the input buffer, and then someone somehow signals the application that the data is ready to be consumed. While an application, or an application server can be written without understanding what goes under the hood, it is often important to understand the IO subsystem to be able to tune high performing servers. The notes on this page try to concisely capture the key concepts in IO subsystem of an operating system, and prepare a stage for understanding the blocking IO, non-blocking IO, and epoll edge triggered channel selection.

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