c multithreading - Serbipunk/notes GitHub Wiki

variable specifier

alignas

struct alignas(64) ThreadData {
    int value;
    // 剩余60字节自动填充，不会与其他数据共享缓存行
};

alignas(float)

alignas is an alignment specifier that lets you manually override the compiler's default alignment for a variable or struct.

struct ThreadData {
    int value;  // alignment: 4
};
// default alignment: 4 bytes

Memory layout (two threads' data could end up in the same cache line): [ ThreadData_A ][ ThreadData_B ] [←————————— 64-byte cache line ——————————→]

alignof()

struct alignas(std::hardware_destructive_interference_size) ThreadData {
    int value;
};