来自纹理串流系统的活动纹理文件 IO 请求的最大数量。
This value limits the maximum number of texture file IO requests, from the texture streaming system, that are active at any one time. If the scene texture content changes significantly and rapidly, the system may attempt to load more texture mipmaps than the file IO can keep up with. Lowering this value will reduce the IO bandwidth generated by the streaming system, resulting in a more rapid response than changing mipmap requirements.