Why is nginx fast?

Why is Nginx so efficient and so fast?

Design principle

The typical characteristics of a high-performance server are high processing speed and low resource consumption. Especially when there are tens of thousands of connections When online at the same time. To achieve fast processing speed, concurrency model design is particularly critical.

The amount of server concurrency depends on two factors: one is the number of processes connected to the server, and the other is the number of processes that each process can process at the same time. The number of concurrent requests, so the server concurrency model consists of two parts, the service provision method and the link processing mechanism.

Because these two unique methods make Nginx perform well among the same type of web servers

Connection method

Generally, web server connection methods are divided into three types: multi-process method, multi-thread method and asynchronous method. Multi-process requires additional overhead such as memory copying, while multi-threading does not require smaller overhead.

Asynchronous uses a non-blocking method to communicate with each client, and the server uses one process for polling. Typical applications include Nginx's work process process. Among them, the most efficient one is asynchronous, the most stable one is multi-process, and the least resource occupancy is multi-threading

Nginx provides services based on the event model (asynchronous mode), which is more suitable for the number of connections per second and the number of requests to be non-linear at the same time growth situation. Even as load increases, the number of memory and CPU usage events remains predictable. Nginx can handle tens of thousands of concurrent connections on a server using ordinary hardware. This is the first reason for Nginx's high performance.

Other things Nginx does

In addition to the above two principles, there are a lot of visible detail optimizations internally, using a multi-process single-thread working method, and The affinity between the CPU and the process is used to bind the process to a specific CPU, avoiding the cost of process context switching, thus reducing CPU usage. In addition, it implements an efficient memory pool, minimizing memory usage, etc.

Connection processing mechanism

linux has five connection models, synchronous io, synchronization fee blocking io, asynchronous blocking io (io multiplexing), asynchronous non-blocking io (signal driven or asynchronous io)

The following are the key points:

<1> io multiplexing, I/O multiplexing When using the model, you will use the select or poll function. These two functions will also block the process. Different from blocking I/O, they can also block multiple I/O operations at the same time, and they can perform multiple read operations at the same time. The I/O functions of multiple write operations are detected, and the I/O operation function is not actually called until data is readable or writable.

In the io reuse model, select and poll are generally supported by the operating system, but each time you wait, you need to set the socket interface that needs to be waited for, and the internal implementation is not efficient enough, which makes it difficult to pay for high concurrency of monitoring. Socket set, different operating systems use different advanced polling techniques to support high-performance monitoring, generally these methods are not portable. Nginx has customized different I/O processing mechanisms for different operating systems, and generally uses the high-performance interface of the operating system. This is the second reason for Nginx's high performance

<2>Asynchronous IO: When an asynchronous procedure call request is issued, the caller cannot get the result immediately. After the component that actually handles this call is completed, it will notify the caller of the input and output operations through status, notifications and callbacks

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