When CONFIG_PSI_DEFAULT_DISABLED=y, the pressure system returns
"operation not supported", rather than permission denied or not
exposing the /proc/pressure files.
Fixes: https://github.com/prometheus/node_exporter/issues/1961
Signed-off-by: Ben Kochie <superq@gmail.com>
This enables the collection of pressure stall information as exposed
by the `/proc/pressure` interface added in the 4.20 release of the
Linux kernel.
Closes#1174
Signed-off-by: Daniele Sluijters <daenney@users.noreply.github.com>