In top, sorting by USED doesn't sort properly.

1) Description: Ubuntu 16.04.1 LTS
   Release: 16.04

2) procps:
     Installed: 2:3.3.10-4ubuntu2
     Candidate: 2:3.3.10-4ubuntu2
     Version table:
    *** 2:3.3.10-4ubuntu2 500
           500 http://us.archive.ubuntu.com/ubuntu xenial/main amd64 Packages
           100 /var/lib/dpkg/status

3) Sorting by `USED` in `top` will produce a list of programs that are sorted in descending order of total memory use.

4) Sorting by `USED` in `top` will produce a list of programs that are seemingly randomly sorted.

====

Procedure:

1) Run `top`.
2) Press uppercase F.
3) Press up arrow or down arrow until you get to USED.
4) Press space to get USED to show up on the main screen.
5) Press lowercase s to sort by USED.
6) Press lowercase q to go back to the main screen.
7) Note that the sorting isn't done properly.

Example output:

2 PID PPID S %MEM USED RES SWAP SHR VIRT COMMAND
 18783 1645 S 9.3 263736 189680 74056 58776 1297844 chrome
  1511 1509 S 0.2 98772 3468 95304 0 712504 FAHClient
 18856 18796 S 6.5 160712 132384 28328 19356 1109696 chrome
 18816 18783 S 2.8 102516 57248 45268 17976 1117556 chrome
 18851 18796 S 5.2 137308 106624 30684 25080 894612 chrome
  1167 1148 S 2.3 82984 46836 36148 7416 433728 Xorg

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: procps 2:3.3.10-4ubuntu2
ProcVersionSignature: Ubuntu 4.4.0-38.57-generic 4.4.19
Uname: Linux 4.4.0-38-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.1
Architecture: amd64
CurrentDesktop: XFCE
Date: Thu Oct 20 23:18:42 2016
EcryptfsInUse: Yes
SourcePackage: procps
UpgradeStatus: No upgrade log present (probably fresh install)