Five common I/O models in Linux

In general, the process of input operation has two steps: ET, relocation.

Under Linux, there are five I/O models, each of which is described below:

1>. Blocking I/O (wide use)

The application calls an I/O function, and if the data is ready, it causes the application to block until the data is ready to be copied from the kernel to the user space (the process cache) and the I/O function returns successfully.

If a process calls Recvform, then the system call does not return until a packet arrives on the local system, and then the data copy is completed.

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2>: Non-blocking I/O (very wasteful CPU resources, infrequently used)

We set up a set of interfaces to be non-blocking, that is, to tell the kernel, when the requested I/O operation cannot be completed, do not sleep the process, but return an error. The I/O operation function continuously tests whether the data is ready, and if the wood is ready to continue testing (polling) until the data is ready and copied from the kernel to the user space, the I/O function returns successfully.

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3>. I/O multiplexing (Utility server program)

Using the Select, poll, Epoll L functions also causes the process to block, but unlike blocking I/O, these functions can block multiple I/O operations at the same time, and can detect multiple I/O operation functions at the same time for several read and write operations, until the data is readable and writable, to actually invoke i/ O operation function, copy from kernel to user space, I/O function returns success.

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4> signal-driven I/O (SIGIO)

We allow the socket interface for signal-driven I/O, and register a signal processing function, the process continues to run without blocking, when the data is ready, the process will receive a sigio signal, you can call the I/O operation function in the signal processing function to process the data.

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5>. asynchronous I/O

Notify us when the kernel copy is complete.

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Five common I/O models in Linux