Comment 13 for bug 1316830

Same here, this time on Debian 3.16.43-2+deb8u1 with kernel 3.16.0-4-amd64. I know this is an Ubuntu forum, but this bug ticket is the closest one for this issue that I could find. Package accountsservice has version 0.6.37-3+b1.

This machine is running ProFTPd 1.3.5 with a high number of FTP sessions.

As you can see the wtmp file gets rather large:
-rw------- 1 root utmp 3072 Jul 14 09:53 btmp
-rw------- 1 root utmp 44259072 Jul 17 16:07 wtmp
-rw------- 1 root utmp 119944320 Jul 17 07:49 wtmp.1
-rw------- 1 root utmp 120503424 Jul 16 07:35 wtmp.2
-rw------- 1 root utmp 120549888 Jul 15 07:35 wtmp.3

This is probably the reason why accounts-daemon is eating away most of by CPU:

  PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
  587 root 20 0 481984 98616 2520 R 73.5 9.6 1204:19 accounts-daemon