Instead of allocating a new buffer on every file, one can (re)use pooled arrays. There is a good Shared ArrayPool implementation inside System.Buffers, which can be used for this purpose. There should not be a memory-leak in case the buffer is not returned to the pool, so the Dispose() method is enough and no destructor is needed. The array returned by the pool could be larger than the requested size, since the size will always be a power of 2. This is why the buffersize is derived from the length of the returned array. This change only affects 4 lines, I don't know why it shows such a large difference.