Golang function performance optimization memory alignment optimization

Memory alignment optimization improves program performance by aligning data to specific addresses. It reduces cache misses and optimizes SIMD instructions. The specific steps are as follows: Use the Alignof function to obtain the minimum alignment value of the type. Allocate aligned memory using the unsafe.Pointer type. Cast the data structure to an aligned type. Practical case: By aligning the different alignment requirements of embedded structures, access to the b field can be optimized, thereby improving cache usage and the performance of SIMD instructions.

Go function performance optimization: memory alignment optimization

Memory alignment refers to when allocating data in memory, according to the data type Ask for it to be placed at a specific address. In Go, you can get the minimum alignment of a value of a specific type by using the Alignof function in the unsafe package.

Why should we perform memory alignment optimization?

Memory alignment can improve program performance for several reasons:

• Reduced cache misses: Modern computers use caches to speed up access to memory Access. When data is not aligned with cache address boundaries, a cache miss results, requiring the data to be retrieved from main memory, thereby increasing access time.
• Optimized SIMD instructions: The SIMD (Single Instruction Multiple Data) instruction set improves performance by processing multiple data values ​​in parallel. Aligned data allows SIMD instructions to execute more efficiently.

How to use memory alignment?

Using memory alignment requires the following steps:

1. Use the Alignof function to obtain the minimum alignment value of the type.
2. Use unsafe.Pointer pointer types to allocate aligned memory.
3. Force the data structure to an aligned type.

The following code example demonstrates how to align a structure:

import (
    "fmt"
    "unsafe"
)

type MyStruct struct {
    a int
    b int64  // 8 字节对齐
    c bool   // 1 字节对齐
}

func main() {
    // 获取 MyStruct 的最小对齐值
    align := unsafe.Alignof(MyStruct{}) // 8

    // 分配对齐的内存
    ptr := unsafe.Pointer(unsafe.Align(unsafe.Pointer(new(MyStruct)), align))

    // 强制转换指针类型
    s := (*MyStruct)(ptr)

    // 对齐后的访问
    s.b = 100
    fmt.Println(s.b) // 输出：100
}

Practical case:

In the following practical case, we will Align a struct that contains an embedded struct that has different alignment requirements:

type EmbeddedStruct struct {
    a int
    b [8]byte  // 8 字节对齐
}

type MyStruct struct {
    EmbeddedStruct
    c bool   // 1 字节对齐
}

By aligning MyStruct, we can optimize the b Field access, thereby improving cache usage and SIMD instruction performance.

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