add documentation

Author: ivelichkovich

docs/reference/gc-commandline-reference.md

@@ -31,6 +31,11 @@ Print usage and exit.
 
 Print version and exit.
 
+### -list-size
+
+The pagination size to use when calling api-server to list nodefeatures. 
+Pagination is useful for controlling the load on api-server/etcd as the nodefeature resources can be large.
+
 ### -gc-interval
 
 The `-gc-interval` specifies the interval between periodic garbage collector runs.

docs/usage/nfd-gc.md

@@ -27,3 +27,10 @@ default garbage collector interval is set to 1h which is the value when no
 In Helm deployments see
 [garbage collector parameters](../deployment/helm.md#garbage-collector-parameters)
 for altering the nfd-gc configuration.
+
+## List Pagination & Scalability
+
+When NFD GC runs up it lists nodefeatures from api-server.
+These resources can be large and in a large cluster this initial list call to sync the informer cache can be
+expensive and heavy on api-server/etcd. You can use the `list-size` argument to control pagination size
+to help control the load from this list.