struct 的排列不同，go 为其分配的内存空间也不同，下面的代码可以看到结果：
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package main
import (
"fmt"
"unsafe"
)
type myStruct struct {
myInt bool // 1 byte
myFloat float64 // 8 bytes
myBool int32 // 4 bytes
}
type myStructOptimized struct {
myFloat float64 // 8 bytes
myInt int32 // 4 bytes
myBool bool // 1 byte
}
func main() {
a := myStruct{}
b := myStructOptimized{}
fmt.Println(unsafe.Sizeof(a)) // unordered 24 bytes
fmt.Println(unsafe.Sizeof(b)) // ordered 16 bytes
}
下面的代码可以验证struct 的内存分配：
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package main
import (
"fmt"
"unsafe"
)
type myStructOptimized struct {
myFloat float64 // 8 bytes
myBool bool // 1 byte
myInt int32 // 4 bytes
}
func main() {
b := myStructOptimized{}
fmt.Println(unsafe.Sizeof(b))
fmt.Println(unsafe.Offsetof(b.myFloat))
fmt.Println(unsafe.Offsetof(b.myBool))
fmt.Println(unsafe.Offsetof(b.myInt))
}
- betteralign struct内存对齐工具 https://github.com/dkorunic/betteralign
- struct 内存可视化工具 https://github.com/ugurkinik/struct-memory-visualization
- resource How to organize the go struct, in order to save memory
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