backoff.hpp

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#ifndef JOIN_CORE_BACKOFF_HPP
#define JOIN_CORE_BACKOFF_HPP
 
// C++.
#include <thread>
 
// C.
#if defined(__x86_64__) || defined(__i386__)
#include <immintrin.h>
#endif
#include <cstddef>
 
namespace join
{
    class Backoff
    {
    public:
        Backoff (size_t spin = 200)
        : _spin (spin)
        , _count (0)
        {
        }
 
        void operator() () noexcept
        {
            if (_count < _spin)
            {
#if defined(__x86_64__) || defined(__i386__)
                _mm_pause ();
#elif defined(__aarch64__) || defined(__arm__)
                __asm__ __volatile__ ("yield" ::: "memory");
#endif
                ++_count;
            }
            else
            {
                std::this_thread::yield ();
            }
        }
 
        void reset () noexcept
        {
            _count = 0;
        }
 
        bool spinExhausted () const noexcept
        {
            return _count >= _spin;
        }
 
    private:
        size_t _spin;
 
        size_t _count;
    };
}
 
#endif