dotnet 读 WPF 源代码笔记 SafeMILHandleMemoryPressure 的作用

        internal SafeMILHandleMemoryPressure(long gcPressure)
        {
            _gcPressure = gcPressure;
            _refCount = 0;


            // Removed WPF specific GC algorithm and all bitmap allocations/deallocations
            // are now tracked with GC.Add/RemoveMemoryPressure.
            GC.AddMemoryPressure(_gcPressure);
        }

        internal void AddRef()
        {
            Interlocked.Increment(ref _refCount);
        }

        internal void Release()
        {
            if (Interlocked.Decrement(ref _refCount) == 0)
            {

                // Removed WPF specific GC algorithm and all bitmap allocations/deallocations
                // are now tracked with GC.Add/RemoveMemoryPressure.
                GC.RemoveMemoryPressure(_gcPressure);
                _gcPressure = 0;
            }
        }

        // Estimated size in bytes of the unmanaged memory
        private long _gcPressure;

        //
        // SafeMILHandleMemoryPressure does its own ref counting in managed code, because the
        // associated memory pressure should be removed when there are no more managed
        // references to the unmanaged resource. There can still be references to it from
        // unmanaged code elsewhere, but that should not prevent the memory pressure from being
        // released.
        //
        private int _refCount;