sysfs: Add preferred CPU file

Add a "preferred" file in /sys/devices/system/cpu/ when kernel is
built with CONFIG_PREFERRED_CPU=y.

This would help
- Users to quickly check which CPUs are marked as preferred.
- Userspace daemons such as irqbalance to use this mask to
  route irqs into preferred CPUs.

For example:
cat /sys/devices/system/cpu/online
0-719
cat /sys/devices/system/cpu/preferred
0-599        <<< Implies 0-599 are preferred for workloads and 600-719
                 should be avoided at this moment.

cat /sys/devices/system/cpu/preferred
0-719        <<< All CPUs are usable. There is no preference.

Signed-off-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260928053728.797539-6-sshegde@linux.ibm.com

0 files changed, 0 insertions, 0 deletions