golang improves cgo

When developing a program, you sometimes need to use the underlying system library, and the cgo mechanism of the Go language can well support the C language. This realizes interaction with the underlying system to a certain extent, and also makes the Go language have A certain degree of cross-platform functionality. However, cgo also has performance problems, especially when frequent calls are prone to performance bottlenecks. Therefore, how to improve the performance of cgo has always been a topic of great concern.

Go language has begun to improve the performance of cgo since version 1.5. This article will introduce some of the current mainstream cgo improvement methods, as well as their advantages and disadvantages.

1. Use the go:linkname directive

go: The linkname directive allows Go language functions to directly call C language functions, avoiding the process of calling functions through the Cgo mechanism. This method can improve the execution efficiency of the program to a certain extent, especially when C language functions are frequently called, the performance is particularly obvious.

For example, we have a source file of hello.c, which implements a function called hello. Now we want to call this function directly in the Golang code. We can do this (hello.c):

#include <stdio.h>
void hello() {
    printf("Hello World
");
}

Define a function named gohello, and then use the go:linkname directive to bind it to the hello function (goh.h):

package main

import "C"

//export gohello
func gohello() {
    //调用hello函数
    hello()
}

//go:linkname hello
func hello()

In this way, we successfully made Golang The program can directly call the hello function, thus avoiding the performance overhead of using cgo.

Disadvantages: Although this method can improve the efficiency of the program, using the go:linkname instruction makes the Go language and C language code highly coupled and reduces readability, which is not conducive to code maintenance and management.

2. Rewrite the system call library

System call libraries in C language are often very large and complex libraries, and the overhead of calling these libraries is relatively large. Therefore, rewriting the system call library is an effective means to improve cgo performance.

For example, the stdio library in Go language is implemented based on the stdio library of C language. But in the Go language, only a small number of functions are used in the stdio library, so it can be simplified and eliminate those useless functions.

Taking file opening as an example, we can use the Open function in the syscall library instead of the open file function in the stdio library. This method can avoid the overhead of using cgo to call the stdio library, thereby improving the efficiency of the program.

Disadvantages: Rewriting the system call library requires a full understanding of the underlying API and corresponding C/C programming experience. For developers who are not familiar with the underlying API, this method may not be practical.

3. Use static inline function in code

The static inline function is a compiler optimization option in C language, which can embed the execution code of the function directly into the function call point , thereby avoiding the overhead of function calls. In Golang code, this option can be specified through CGO_PREFIX_CFLAGS and CGO_PREFIX_LDFLAGS.

For example, we have a source file hello.c, which implements a function called hello. At this time, we can use CGO_PREFIX_CFLAGS and CGO_PREFIX_LDFLAGS in the Golang code to instruct the compiler to use the static inline optimization option.

package main
/*
#cgo CFLAGS: -std=c99 -O2  -D _GNU_SOURCE
#cgo LDFLAGS:
#include <stdio.h>
static inline void  hello() {
    printf("hello from cgo inline function. 
");
}
*/
import "C"

func main(){
    C.hello()
}

This method can reduce the cost of function calls and improve the execution efficiency of the program.

Disadvantages: Although this method has a simple interface and is easy to use, it is only suitable for use when the function is simple and the amount of code is small. This method is not suitable for scenarios involving large-scale libraries or complex underlying APIs.

Summary:

The cgo mechanism has contributed to the cross-platform nature of the Go language, but due to the overhead of using Cgo, program performance often cannot be improved well. Therefore, improving the performance of cgo has become a hot topic in the Go language community. This article introduces the mainstream cgo improvement methods to help readers understand cgo and use it better. Different scenarios are suitable for different improvement methods, and developers should choose the solution that best suits their needs in the actual scenario.

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