[TOC] ## 共享內存 - 不同進程之間內存空間是獨立的，也就是說進程不能訪問也不會干擾其他進程的內存 - 如果兩個進程希望通過共享內存的方式通信,可以通過`mmap()`系統調用實現 - 共享內存是效率最高的進程間通訊機制，因為數據不需要在內核和程序之間復制 ### go 實現 <details> <summary>shm_writer.go</summary> ``` package main /* #cgo linux LDFLAGS: -lrt #include <fcntl.h> #include <unistd.h> #include <sys/mman.h> #define FILE_MODE (S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH) int my_shm_new(char *name) { shm_unlink(name); return shm_open(name, O_RDWR|O_CREAT|O_EXCL, FILE_MODE); } */ import "C" import ( "fmt" "unsafe" ) const SHM_NAME = "my_shm" const SHM_SIZE = 4 * 1000 * 1000 * 1000 type MyData struct { Col1 int Col2 int Col3 int } func main() { fd, err := C.my_shm_new(C.CString(SHM_NAME)) if err != nil { fmt.Println(err) return } C.ftruncate(fd, SHM_SIZE) ptr, err := C.mmap(nil, SHM_SIZE, C.PROT_READ|C.PROT_WRITE, C.MAP_SHARED, fd, 0) if err != nil { fmt.Println(err) return } C.close(fd) data := (*MyData)(unsafe.Pointer(ptr)) data.Col1 = 100 data.Col2 = 876 data.Col3 = 8021 } ``` </details> <br/> <details> <summary>shm_reader.go</summary> ``` package main /* #cgo linux LDFLAGS: -lrt #include <fcntl.h> #include <unistd.h> #include <sys/mman.h> #define FILE_MODE (S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH) int my_shm_open(char *name) { return shm_open(name, O_RDWR, FILE_MODE); } */ import "C" import ( "fmt" "unsafe" ) const SHM_NAME = "my_shm" const SHM_SIZE = 4 * 1000 * 1000 * 1000 type MyData struct { Col1 int Col2 int Col3 int } func main() { fd, err := C.my_shm_open(C.CString(SHM_NAME)) if err != nil { fmt.Println(err) return } ptr, err := C.mmap(nil, SHM_SIZE, C.PROT_READ|C.PROT_WRITE, C.MAP_SHARED, fd, 0) if err != nil { fmt.Println(err) return } C.close(fd) data := (*MyData)(unsafe.Pointer(ptr)) fmt.Println(data) } ``` </details> <br/>