Shulou(Shulou.com)06/03 Report--

Pipe is an inter-process communication mechanism inherited by Linux from Unix, and it is an important communication mechanism in the early days of Unix. The idea is to create a shared file in memory so that both sides of the communication can use the shared file to transmit information. Because this method has the characteristic of one-way transmission of data, the shared file that is used as the delivery message is called "pipeline".

In the specific implementation of the pipe, there are "anonymous pipe" and "named pipe" depending on whether the file used for communication has a name or not.

The difference between pipes and shared memory

At first glance, it doesn't feel very different between pipes and shared memory. Here's a look at the difference between the two:

The ● pipeline requires four copies of the data in the kernel and user space: from the user space buf to the kernel-> the kernel copies the data to memory-> memory to the kernel-> the kernel to the user space buf. Shared memory copies data only twice: user space to memory-> memory to user space.

The ● pipeline is implemented in a circular queue, and the continuous transmission of data can be unlimited in size. The data size of each transfer in shared memory is fixed.

● shared memory can randomly access any location of the mapped file, and pipes can only read and write sequentially.

● pipeline can independently complete the data transmission and notification mechanism, shared memory needs to use other means of communication for message delivery.

In other words, the biggest difference between the two is that the shared memory area is the fastest available IPC form. Once such a memory area is mapped to the address space of the process that shares it, the transfer of data between these processes will no longer be done by performing any system calls into the kernel to transfer each other's data, saving time.

This is the linux. What is the pipeline? For more details, please pay attention to other related articles!

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