oeqa.buildperf: functionality to drop kernel caches
Add a new utility class for dropping Linux kernel caches. It uses sudo
and tee to write to the drop_caches file. Checking if the user has the
permissions to drop caches (without a password) is done by trying to
writing an invalid value to the drop_caches file. This way, we will find
if writing (with tee) is possible but not really dropping caches, yet.
User can avoid giving the password by adding something like:
<user> ALL = NOPASSWD: /usr/bin/tee /proc/sys/vm/drop_caches
to the system sudoers file.
Signed-off-by: Markus Lehtonen <markus.lehtonen@linux.intel.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
