linux-master/mm/vmscan.c

6  *  kswapd added: 7.1.96  sct
9  *  Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com).
472 	 * If kswapd is disabled, reschedule if necessary but do not
506 	 * Do not throttle user workers, kthreads other than kswapd or
931 	 * demote or reclaim pages from the target node via kswapd if we are
1064 		 * reclaim_congested. kswapd will stall and start writing
1283 			 * Only kswapd can writeback filesystem folios
1529 	 * we are not kswapd and therefore cannot write dirty file pages. But
4716 	/* kswapd should abort if all eligible zones are safe */
4944 	/* kswapd should never fail */
5668 	 * reclaiming implies that kswapd is not keeping up and it is best to
5698 		 * For kswapd and memcg, reclaim at least the number of pages
5935 		 * Once a node is flagged PGDAT_WRITEBACK, kswapd will
5943 		/* Allow kswapd to start writing pages during reclaim.*/
5948 		 * If kswapd scans pages marked for immediate
5975 	 * node is congested. Allow kswapd to continue until it
5992 	 * successful direct reclaim run will revive a dormant kswapd.
6052 	 * Do not throttle kswapd or cgroup reclaim on NOPROGRESS as it will
6314 	/* kswapd must be awake if processes are being throttled */
6328  * depleted. kswapd will continue to make progress and wake the processes
6365 	 * wait on a queue until kswapd makes progress and wakes them. There
6395 	 * it is not safe to block on pfmemalloc_wait as kswapd could be
6403 		/* Throttle until kswapd wakes the process */
6620 	 * allocation tries to wake a remote kswapd.
6640  * Prepare kswapd for sleeping. This verifies that there are no processes
6643  * Returns true if kswapd is ready to sleep
6651 	 * race between when kswapd checks the watermarks and a process gets
6653 	 * throttled, kswapd wakes, a large process exits thereby balancing the
6654 	 * zones, which causes kswapd to exit balance_pgdat() before reaching
6655 	 * the wake up checks. If kswapd is going to sleep, no process should
6657 	 * the wake up is premature, processes will wake kswapd and get
6677  * kswapd shrinks a node of pages that are at or below the highest usable
6680  * Returns true if kswapd scanned at least the requested number of pages to
6752  * For kswapd, balance_pgdat() will reclaim pages across a node from zones
6756  * Returns the order kswapd finished reclaiming at.
6758  * kswapd scans the zones in the highmem->normal->dma direction.  It skips
6789 	 * stall or direct reclaim until kswapd is finished.
6822 		 * request are balanced to avoid excessive reclaim from kswapd.
6840 		 * re-evaluate if boosting is required when kswapd next wakes.
6907 		/* Check if kswapd should be suspending */
6977 	 * Return the order kswapd stopped reclaiming at as
6979 	 * entered the allocator slow path while kswapd was awake, order will
6987  * be reclaimed by kswapd from the waker. If the value is MAX_NR_ZONES which is
6988  * not a valid index then either kswapd runs for first time or kswapd couldn't
6990  * case return the zone index of the previous kswapd reclaim cycle.
7022 		 * When kswapd is going to sleep, it is reasonable to assume
7066 		 * per-cpu vmstat threshold while kswapd is awake and restore
7097 static int kswapd(void *p)
7111 	 * regardless (see "__alloc_pages()"). "kswapd" should
7156 		 * reclaim fails then kswapd falls back to reclaiming for
7157 		 * order-0. If that happens, kswapd will consider sleeping
7177  * kswapd should reclaim (direct reclaim is deferred), wake it up for the zone's
7178  * pgdat.  It will wake up kcompactd after reclaiming memory.  If kswapd reclaim
7267  * This kswapd start function will be called by init and node-hot-add.
7274 	if (!pgdat->kswapd) {
7275 		pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid);
7276 		if (IS_ERR(pgdat->kswapd)) {
7278 			pr_err("Failed to start kswapd on node %d���ret=%ld\n",
7279 				   nid, PTR_ERR(pgdat->kswapd));
7281 			pgdat->kswapd = NULL;
7294 	struct task_struct *kswapd;
7297 	kswapd = pgdat->kswapd;
7298 	if (kswapd) {
7299 		kthread_stop(kswapd);
7300 		pgdat->kswapd = NULL;