std::hardware_destructive_interference_size, std::hardware_constructive_interference_size

< cpp‎ | thread
Defined in header <new>
inline constexpr std::size_t
    hardware_destructive_interference_size = /*implementation-defined*/;
(1) (since C++17)
inline constexpr std::size_t
    hardware_constructive_interference_size = /*implementation-defined*/;
(2) (since C++17)
1) Minimum offset between two objects to avoid false sharing. Guaranteed to be at least alignof(std::max_align_t)
struct keep_apart {
  alignas(std::hardware_destructive_interference_size) std::atomic<int> cat;
  alignas(std::hardware_destructive_interference_size) std::atomic<int> dog;
2) Maximum size of contiguous memory to promote true sharing. Guaranteed to be at least alignof(std::max_align_t)
struct together {
  std::atomic<int> dog;
  int puppy;
struct kennel {
  // Other data members...
  alignas(sizeof(together)) together pack;
  // Other data members...
static_assert(sizeof(together) <= std::hardware_constructive_interference_size);


These constants provide a portable way to access the L1 data cache line size.


See also

returns the number of concurrent threads supported by the implementation
(public static member function of std::thread)