// SPDX-License-Identifier: GPL-2.0
/*
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *
 *  Swap reorganised 29.12.95, Stephen Tweedie.
 *  kswapd added: 7.1.96  sct
 *  Removed kswapd_ctl limits, and swap out as many pages as needed
 *  to bring the system back to freepages.high: 2.4.97, Rik van Riel.
 *  Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
 *  Multiqueue VM started 5.8.00, Rik van Riel.
 */

/* Extracted unchanged from Linux v6.0, mm/vmscan.c:3425-3453.
 * Complete function definition; surrounding kernel context is required.
 * Source: https://github.com/torvalds/linux/blob/v6.0/mm/vmscan.c#L3425
 * License text: GPL-2.0.txt (in this directory).
 */
static void consider_reclaim_throttle(pg_data_t *pgdat, struct scan_control *sc)
{
	/*
	 * If reclaim is making progress greater than 12% efficiency then
	 * wake all the NOPROGRESS throttled tasks.
	 */
	if (sc->nr_reclaimed > (sc->nr_scanned >> 3)) {
		wait_queue_head_t *wqh;

		wqh = &pgdat->reclaim_wait[VMSCAN_THROTTLE_NOPROGRESS];
		if (waitqueue_active(wqh))
			wake_up(wqh);

		return;
	}

	/*
	 * Do not throttle kswapd or cgroup reclaim on NOPROGRESS as it will
	 * throttle on VMSCAN_THROTTLE_WRITEBACK if there are too many pages
	 * under writeback and marked for immediate reclaim at the tail of the
	 * LRU.
	 */
	if (current_is_kswapd() || cgroup_reclaim(sc))
		return;

	/* Throttle if making no progress at high prioities. */
	if (sc->priority == 1 && !sc->nr_reclaimed)
		reclaim_throttle(pgdat, VMSCAN_THROTTLE_NOPROGRESS);
}