Comment 10 for bug 746508

After updating the Ubuntu servers I maintain on the 30 of September I'm having this problem too. However only on one of the servers which is currently running Ubuntu 14.04.5 LTS (3.13.0-96-generic #143-Ubuntu SMP Mon Aug 29 20:15:20 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux).

If I run apt-check manually with the following command:
# /usr/lib/update-notifier/apt-check --human-readable
0 packages can be updated.
0 updates are security updates.

It outputs quite quickly but running apt-get update tends to cause multiple processes of
'apt-check --human-readable' and causes high load.

top shows the following:
##
top - 11:00:03 up 11 days, 10:28, 1 user, load average: 28.85, 16.79, 7.03
Tasks: 279 total, 9 running, 266 sleeping, 0 stopped, 4 zombie
%Cpu(s): 20.5 us, 7.7 sy, 0.1 ni, 70.5 id, 1.1 wa, 0.0 hi, 0.1 si, 0.0 st
KiB Mem: 1013868 total, 943524 used, 70344 free, 664 buffers
KiB Swap: 1046524 total, 58400 used, 988124 free. 505288 cached Mem

 PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
15494 root 39 19 121672 34420 21224 D 4.5 3.4 0:03.18 apt-check
15650 root 39 19 121672 34260 21060 R 4.5 3.4 0:03.21 apt-check
16038 root 39 19 121676 34744 21532 D 4.5 3.4 0:03.22 apt-check
16144 root 39 19 121676 35260 22052 D 4.5 3.5 0:03.17 apt-check
16642 root 39 19 103884 28516 19756 D 4.5 2.8 0:02.48 apt-check

htop shows mostly the same but with instead of apt-check gives more info about the command:
'/usr/bin/python /usr/lib/update-notifier/apt-check --human-readable'

The server also shows more average load across the board in vSphere. CPU% has increase from normally 6% to average of 33%. However I'm not sure if this is related.

Also found a tread on serverfault with the same issue: http://serverfault.com/questions/471089/prevent-apt-check-from-eating-all-my-memory