linux/mm/vmscan.c

2500 		 * approach the memory protection threshold, to totally
2502 		 * setting extremely liberal protection thresholds. It
2503 		 * also means we simply get no protection at all if we
2506 		 * If there is any protection in place, we reduce scan
2508 		 * within protection thresholds.
2512 		 * protection. If that fails to reclaim enough pages to
2514 		 * the best-effort low protection. However, we still
2520 		 * hard protection.
2523 		unsigned long protection;
2527 			protection = low;
2530 			protection = min;
2533 		/* Avoid TOCTOU with earlier protection check */
2534 		cgroup_size = max(cgroup_size, protection);
2536 		scan -= scan * protection / (cgroup_size + 1);
3175  * turn off protection when SP>PV or turn on protection when SP<PV.
4103  *                          working set protection
6030 			 * Hard protection.
6036 			 * Soft protection.
6037 			 * Respect the protection only as long as