GitLab

The tc action act_nat was using shared stats and taking the per action
lock in the datapath. Improve it by using percpu stats and rcu.

perf before:
- 10.48% tcf_nat_act
   - 81.83% _raw_spin_lock
        81.08% native_queued_spin_lock_slowpath

perf after:
- 0.48% tcf_nat_act

tdc results:
1..27
ok 1 7565 - Add nat action on ingress with default control action
ok 2 fd79 - Add nat action on ingress with pipe control action
ok 3 eab9 - Add nat action on ingress with continue control action
ok 4 c53a - Add nat action on ingress with reclassify control action
ok 5 76c9 - Add nat action on ingress with jump control action
ok 6 24c6 - Add nat action on ingress with drop control action
ok 7 2120 - Add nat action on ingress with maximum index value
ok 8 3e9d - Add nat action on ingress with invalid index value
ok 9 f6c9 - Add nat action on ingress with invalid IP address
ok 10 be25 - Add nat action on ingress with invalid argument
ok 11 a7bd - Add nat action...