Ffmpeg decoding multiple H264 video streams takes too much video RAM

My ubuntu server has RTX3090 card, I want to use it to decode multiple H264 video streams. I tried to start 50 processes to run ffmpeg command to get and decode 50 H264 video streams.

On every process, I run below command:
ffmpeg -c:v h264_cuvid -i rtsp://192.168.3.150:554/live/test_1 -y -f image2 -r 1/1 img_0_%04d.jpg

It is to use hardware decoder(h264_cuvid) to decode H264 RTSP stream, and save one picture every one second.

When I ran those 50 processes, I checked the 3090 video RAM, it took 18575MB video RAM. Why does it take so much video RAM?

Can anyone help on this?

Do you have any evidense it took less before?

No. Just feel it is too much if one video decoder takes about 370M GPU RAM.