Detector gets slower in a for loop

[gitlabspy]

import cv2
import face_detection
detector = face_detection.build_detector(
  "DSFDDetector", confidence_threshold=.5, nms_iou_threshold=.3)
for im in imgs:
  detector.detect(im)
  save...

I am using one GPU(V100 32G) to detect these imgs. At first, it used about 7800M VRAM then later it stabilize at 28100M but the speed gets much slower.
It was very fast at the beginning altho it spends some time for startup. It was like 200 imgs processed in 2min or 3min? Now it takes 10-20s to process one. All images are almost same size.
What's wrong with my code above? Any tips on process large amount of images?

[gitlabspy]

It turns out it was my problem. Sorry for reporting an false issue. 😢