My node is up since 4 days and seems to eat 7GB of RAM.. that's with version 0.17.1.3. I think it never needed so much RAM before?
top says:
  PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND
    7 root      20   0  0.103t 7.432g 6.664g S   5.7 29.7 179:12.38 monerod