VAAPI usage monitoring

I have Intel Core-i7 8650U processor. I transcode video with ffmpeg. I take attempts to accelerate it. Now I use VAAPI codecs in ffmpeg (h264_vaapi) and vaapi rescaling (scale_vaapi) in filters. And when I use them my CPU load is not on maximum, but framerate doesn't insrease more. So I think that VAAPI's resources are over. **So I have to monitor the usage of Intel graphics hardware that is in my CPU. Is there any API or tool that could show usage of this hardware?** (It would be cool to know both tool(like **htop**) and opportunity to request it at moment from any script (like **ps aux**) or at least one of them). For CPU it's htop For NVIDIA GPUs it's nvidia-smi **For VAAPI it's ...?**