Automatic merge from submit-queue
Avoid unnecessary allocation
This is supposed to avoid unnecessary memory allocations.
PodToSelectableFields seems to be the biggest contributor to memory allocations:
```
Showing top 10 nodes out of 247 (cum >= 83166442)
flat flat% sum% cum cum%
1796823715 31.09% 31.09% 1796823715 31.09% k8s.io/kubernetes/pkg/registry/core/pod.PodToSelectableFields
530856268 9.19% 40.28% 530856268 9.19% k8s.io/kubernetes/pkg/storage.NamespaceKeyFunc
241505351 4.18% 44.46% 241505351 4.18% reflect.unsafe_New
...
```