Apache -DFOREGROUND is still running I/O after the download is stopped

I use docker-compose to run nextcloud,current version is Nextcloud Hub 3 (25.0.2),this is my docker-compose.yml:

version: '3'

services:
  app:
    image: nextcloud:latest
    restart: always
    user: 1000:1001
    ports:
      - 5885:80
    volumes:
      - /data/next-cloud:/var/www/html
      - /mnt/Nas:/var/Storage/Nas
      - /mnt/Nas1:/var/Storage/Nas1
    environment:
      - MYSQL_PASSWORD=xxx
      - MYSQL_DATABASE=nextcloud
      - MYSQL_USER=nextcloud
      - MYSQL_HOST=mariadb-app
    networks:
      - mariadb-net

networks:
  mariadb-net:
    external: true

/mnt/Nas and /mnt/Nas1 are two hard disks that are mounted at host,I created two external_storages to make nextcloud access them.

I found that everything is normal when using nextcloud desktop to download,the speed of downloading is ok(100MB/s for my internal network), but when downloading on the web interface or webdav,the speed is slow(<50MB/s), and even I paused it, apache -DFOREGROUND is still reading in the background.

Here is server’s status after I removed downloading task of web interface for 1 minute: