/usr/lib/linux-tools/4.4.0-81-lowlatency/perf is in linux-tools-4.4.0-81-lowlatency 4.4.0-81.104~14.04.1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/linux-tools/4.4.0-81-lowlatency/../../linux-lts-xenial-tools-4.4.0-81/perf