xref: /openbmc/linux/mm/swap.c (revision 87c2ce3b)
1 /*
2  *  linux/mm/swap.c
3  *
4  *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
5  */
6 
7 /*
8  * This file contains the default values for the opereation of the
9  * Linux VM subsystem. Fine-tuning documentation can be found in
10  * Documentation/sysctl/vm.txt.
11  * Started 18.12.91
12  * Swap aging added 23.2.95, Stephen Tweedie.
13  * Buffermem limits added 12.3.98, Rik van Riel.
14  */
15 
16 #include <linux/mm.h>
17 #include <linux/sched.h>
18 #include <linux/kernel_stat.h>
19 #include <linux/swap.h>
20 #include <linux/mman.h>
21 #include <linux/pagemap.h>
22 #include <linux/pagevec.h>
23 #include <linux/init.h>
24 #include <linux/module.h>
25 #include <linux/mm_inline.h>
26 #include <linux/buffer_head.h>	/* for try_to_release_page() */
27 #include <linux/module.h>
28 #include <linux/percpu_counter.h>
29 #include <linux/percpu.h>
30 #include <linux/cpu.h>
31 #include <linux/notifier.h>
32 #include <linux/init.h>
33 
34 /* How many pages do we try to swap or page in/out together? */
35 int page_cluster;
36 
37 void put_page(struct page *page)
38 {
39 	if (unlikely(PageCompound(page))) {
40 		page = (struct page *)page_private(page);
41 		if (put_page_testzero(page)) {
42 			void (*dtor)(struct page *page);
43 
44 			dtor = (void (*)(struct page *))page[1].mapping;
45 			(*dtor)(page);
46 		}
47 		return;
48 	}
49 	if (put_page_testzero(page))
50 		__page_cache_release(page);
51 }
52 EXPORT_SYMBOL(put_page);
53 
54 /*
55  * Writeback is about to end against a page which has been marked for immediate
56  * reclaim.  If it still appears to be reclaimable, move it to the tail of the
57  * inactive list.  The page still has PageWriteback set, which will pin it.
58  *
59  * We don't expect many pages to come through here, so don't bother batching
60  * things up.
61  *
62  * To avoid placing the page at the tail of the LRU while PG_writeback is still
63  * set, this function will clear PG_writeback before performing the page
64  * motion.  Do that inside the lru lock because once PG_writeback is cleared
65  * we may not touch the page.
66  *
67  * Returns zero if it cleared PG_writeback.
68  */
69 int rotate_reclaimable_page(struct page *page)
70 {
71 	struct zone *zone;
72 	unsigned long flags;
73 
74 	if (PageLocked(page))
75 		return 1;
76 	if (PageDirty(page))
77 		return 1;
78 	if (PageActive(page))
79 		return 1;
80 	if (!PageLRU(page))
81 		return 1;
82 
83 	zone = page_zone(page);
84 	spin_lock_irqsave(&zone->lru_lock, flags);
85 	if (PageLRU(page) && !PageActive(page)) {
86 		list_del(&page->lru);
87 		list_add_tail(&page->lru, &zone->inactive_list);
88 		inc_page_state(pgrotated);
89 	}
90 	if (!test_clear_page_writeback(page))
91 		BUG();
92 	spin_unlock_irqrestore(&zone->lru_lock, flags);
93 	return 0;
94 }
95 
96 /*
97  * FIXME: speed this up?
98  */
99 void fastcall activate_page(struct page *page)
100 {
101 	struct zone *zone = page_zone(page);
102 
103 	spin_lock_irq(&zone->lru_lock);
104 	if (PageLRU(page) && !PageActive(page)) {
105 		del_page_from_inactive_list(zone, page);
106 		SetPageActive(page);
107 		add_page_to_active_list(zone, page);
108 		inc_page_state(pgactivate);
109 	}
110 	spin_unlock_irq(&zone->lru_lock);
111 }
112 
113 /*
114  * Mark a page as having seen activity.
115  *
116  * inactive,unreferenced	->	inactive,referenced
117  * inactive,referenced		->	active,unreferenced
118  * active,unreferenced		->	active,referenced
119  */
120 void fastcall mark_page_accessed(struct page *page)
121 {
122 	if (!PageActive(page) && PageReferenced(page) && PageLRU(page)) {
123 		activate_page(page);
124 		ClearPageReferenced(page);
125 	} else if (!PageReferenced(page)) {
126 		SetPageReferenced(page);
127 	}
128 }
129 
130 EXPORT_SYMBOL(mark_page_accessed);
131 
132 /**
133  * lru_cache_add: add a page to the page lists
134  * @page: the page to add
135  */
136 static DEFINE_PER_CPU(struct pagevec, lru_add_pvecs) = { 0, };
137 static DEFINE_PER_CPU(struct pagevec, lru_add_active_pvecs) = { 0, };
138 
139 void fastcall lru_cache_add(struct page *page)
140 {
141 	struct pagevec *pvec = &get_cpu_var(lru_add_pvecs);
142 
143 	page_cache_get(page);
144 	if (!pagevec_add(pvec, page))
145 		__pagevec_lru_add(pvec);
146 	put_cpu_var(lru_add_pvecs);
147 }
148 
149 void fastcall lru_cache_add_active(struct page *page)
150 {
151 	struct pagevec *pvec = &get_cpu_var(lru_add_active_pvecs);
152 
153 	page_cache_get(page);
154 	if (!pagevec_add(pvec, page))
155 		__pagevec_lru_add_active(pvec);
156 	put_cpu_var(lru_add_active_pvecs);
157 }
158 
159 static void __lru_add_drain(int cpu)
160 {
161 	struct pagevec *pvec = &per_cpu(lru_add_pvecs, cpu);
162 
163 	/* CPU is dead, so no locking needed. */
164 	if (pagevec_count(pvec))
165 		__pagevec_lru_add(pvec);
166 	pvec = &per_cpu(lru_add_active_pvecs, cpu);
167 	if (pagevec_count(pvec))
168 		__pagevec_lru_add_active(pvec);
169 }
170 
171 void lru_add_drain(void)
172 {
173 	__lru_add_drain(get_cpu());
174 	put_cpu();
175 }
176 
177 /*
178  * This path almost never happens for VM activity - pages are normally
179  * freed via pagevecs.  But it gets used by networking.
180  */
181 void fastcall __page_cache_release(struct page *page)
182 {
183 	unsigned long flags;
184 	struct zone *zone = page_zone(page);
185 
186 	spin_lock_irqsave(&zone->lru_lock, flags);
187 	if (TestClearPageLRU(page))
188 		del_page_from_lru(zone, page);
189 	if (page_count(page) != 0)
190 		page = NULL;
191 	spin_unlock_irqrestore(&zone->lru_lock, flags);
192 	if (page)
193 		free_hot_page(page);
194 }
195 
196 EXPORT_SYMBOL(__page_cache_release);
197 
198 /*
199  * Batched page_cache_release().  Decrement the reference count on all the
200  * passed pages.  If it fell to zero then remove the page from the LRU and
201  * free it.
202  *
203  * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
204  * for the remainder of the operation.
205  *
206  * The locking in this function is against shrink_cache(): we recheck the
207  * page count inside the lock to see whether shrink_cache grabbed the page
208  * via the LRU.  If it did, give up: shrink_cache will free it.
209  */
210 void release_pages(struct page **pages, int nr, int cold)
211 {
212 	int i;
213 	struct pagevec pages_to_free;
214 	struct zone *zone = NULL;
215 
216 	pagevec_init(&pages_to_free, cold);
217 	for (i = 0; i < nr; i++) {
218 		struct page *page = pages[i];
219 		struct zone *pagezone;
220 
221 		if (!put_page_testzero(page))
222 			continue;
223 
224 		pagezone = page_zone(page);
225 		if (pagezone != zone) {
226 			if (zone)
227 				spin_unlock_irq(&zone->lru_lock);
228 			zone = pagezone;
229 			spin_lock_irq(&zone->lru_lock);
230 		}
231 		if (TestClearPageLRU(page))
232 			del_page_from_lru(zone, page);
233 		if (page_count(page) == 0) {
234 			if (!pagevec_add(&pages_to_free, page)) {
235 				spin_unlock_irq(&zone->lru_lock);
236 				__pagevec_free(&pages_to_free);
237 				pagevec_reinit(&pages_to_free);
238 				zone = NULL;	/* No lock is held */
239 			}
240 		}
241 	}
242 	if (zone)
243 		spin_unlock_irq(&zone->lru_lock);
244 
245 	pagevec_free(&pages_to_free);
246 }
247 
248 /*
249  * The pages which we're about to release may be in the deferred lru-addition
250  * queues.  That would prevent them from really being freed right now.  That's
251  * OK from a correctness point of view but is inefficient - those pages may be
252  * cache-warm and we want to give them back to the page allocator ASAP.
253  *
254  * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()
255  * and __pagevec_lru_add_active() call release_pages() directly to avoid
256  * mutual recursion.
257  */
258 void __pagevec_release(struct pagevec *pvec)
259 {
260 	lru_add_drain();
261 	release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
262 	pagevec_reinit(pvec);
263 }
264 
265 EXPORT_SYMBOL(__pagevec_release);
266 
267 /*
268  * pagevec_release() for pages which are known to not be on the LRU
269  *
270  * This function reinitialises the caller's pagevec.
271  */
272 void __pagevec_release_nonlru(struct pagevec *pvec)
273 {
274 	int i;
275 	struct pagevec pages_to_free;
276 
277 	pagevec_init(&pages_to_free, pvec->cold);
278 	for (i = 0; i < pagevec_count(pvec); i++) {
279 		struct page *page = pvec->pages[i];
280 
281 		BUG_ON(PageLRU(page));
282 		if (put_page_testzero(page))
283 			pagevec_add(&pages_to_free, page);
284 	}
285 	pagevec_free(&pages_to_free);
286 	pagevec_reinit(pvec);
287 }
288 
289 /*
290  * Add the passed pages to the LRU, then drop the caller's refcount
291  * on them.  Reinitialises the caller's pagevec.
292  */
293 void __pagevec_lru_add(struct pagevec *pvec)
294 {
295 	int i;
296 	struct zone *zone = NULL;
297 
298 	for (i = 0; i < pagevec_count(pvec); i++) {
299 		struct page *page = pvec->pages[i];
300 		struct zone *pagezone = page_zone(page);
301 
302 		if (pagezone != zone) {
303 			if (zone)
304 				spin_unlock_irq(&zone->lru_lock);
305 			zone = pagezone;
306 			spin_lock_irq(&zone->lru_lock);
307 		}
308 		if (TestSetPageLRU(page))
309 			BUG();
310 		add_page_to_inactive_list(zone, page);
311 	}
312 	if (zone)
313 		spin_unlock_irq(&zone->lru_lock);
314 	release_pages(pvec->pages, pvec->nr, pvec->cold);
315 	pagevec_reinit(pvec);
316 }
317 
318 EXPORT_SYMBOL(__pagevec_lru_add);
319 
320 void __pagevec_lru_add_active(struct pagevec *pvec)
321 {
322 	int i;
323 	struct zone *zone = NULL;
324 
325 	for (i = 0; i < pagevec_count(pvec); i++) {
326 		struct page *page = pvec->pages[i];
327 		struct zone *pagezone = page_zone(page);
328 
329 		if (pagezone != zone) {
330 			if (zone)
331 				spin_unlock_irq(&zone->lru_lock);
332 			zone = pagezone;
333 			spin_lock_irq(&zone->lru_lock);
334 		}
335 		if (TestSetPageLRU(page))
336 			BUG();
337 		if (TestSetPageActive(page))
338 			BUG();
339 		add_page_to_active_list(zone, page);
340 	}
341 	if (zone)
342 		spin_unlock_irq(&zone->lru_lock);
343 	release_pages(pvec->pages, pvec->nr, pvec->cold);
344 	pagevec_reinit(pvec);
345 }
346 
347 /*
348  * Try to drop buffers from the pages in a pagevec
349  */
350 void pagevec_strip(struct pagevec *pvec)
351 {
352 	int i;
353 
354 	for (i = 0; i < pagevec_count(pvec); i++) {
355 		struct page *page = pvec->pages[i];
356 
357 		if (PagePrivate(page) && !TestSetPageLocked(page)) {
358 			try_to_release_page(page, 0);
359 			unlock_page(page);
360 		}
361 	}
362 }
363 
364 /**
365  * pagevec_lookup - gang pagecache lookup
366  * @pvec:	Where the resulting pages are placed
367  * @mapping:	The address_space to search
368  * @start:	The starting page index
369  * @nr_pages:	The maximum number of pages
370  *
371  * pagevec_lookup() will search for and return a group of up to @nr_pages pages
372  * in the mapping.  The pages are placed in @pvec.  pagevec_lookup() takes a
373  * reference against the pages in @pvec.
374  *
375  * The search returns a group of mapping-contiguous pages with ascending
376  * indexes.  There may be holes in the indices due to not-present pages.
377  *
378  * pagevec_lookup() returns the number of pages which were found.
379  */
380 unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
381 		pgoff_t start, unsigned nr_pages)
382 {
383 	pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
384 	return pagevec_count(pvec);
385 }
386 
387 unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
388 		pgoff_t *index, int tag, unsigned nr_pages)
389 {
390 	pvec->nr = find_get_pages_tag(mapping, index, tag,
391 					nr_pages, pvec->pages);
392 	return pagevec_count(pvec);
393 }
394 
395 EXPORT_SYMBOL(pagevec_lookup_tag);
396 
397 #ifdef CONFIG_SMP
398 /*
399  * We tolerate a little inaccuracy to avoid ping-ponging the counter between
400  * CPUs
401  */
402 #define ACCT_THRESHOLD	max(16, NR_CPUS * 2)
403 
404 static DEFINE_PER_CPU(long, committed_space) = 0;
405 
406 void vm_acct_memory(long pages)
407 {
408 	long *local;
409 
410 	preempt_disable();
411 	local = &__get_cpu_var(committed_space);
412 	*local += pages;
413 	if (*local > ACCT_THRESHOLD || *local < -ACCT_THRESHOLD) {
414 		atomic_add(*local, &vm_committed_space);
415 		*local = 0;
416 	}
417 	preempt_enable();
418 }
419 
420 #ifdef CONFIG_HOTPLUG_CPU
421 
422 /* Drop the CPU's cached committed space back into the central pool. */
423 static int cpu_swap_callback(struct notifier_block *nfb,
424 			     unsigned long action,
425 			     void *hcpu)
426 {
427 	long *committed;
428 
429 	committed = &per_cpu(committed_space, (long)hcpu);
430 	if (action == CPU_DEAD) {
431 		atomic_add(*committed, &vm_committed_space);
432 		*committed = 0;
433 		__lru_add_drain((long)hcpu);
434 	}
435 	return NOTIFY_OK;
436 }
437 #endif /* CONFIG_HOTPLUG_CPU */
438 #endif /* CONFIG_SMP */
439 
440 #ifdef CONFIG_SMP
441 void percpu_counter_mod(struct percpu_counter *fbc, long amount)
442 {
443 	long count;
444 	long *pcount;
445 	int cpu = get_cpu();
446 
447 	pcount = per_cpu_ptr(fbc->counters, cpu);
448 	count = *pcount + amount;
449 	if (count >= FBC_BATCH || count <= -FBC_BATCH) {
450 		spin_lock(&fbc->lock);
451 		fbc->count += count;
452 		spin_unlock(&fbc->lock);
453 		count = 0;
454 	}
455 	*pcount = count;
456 	put_cpu();
457 }
458 EXPORT_SYMBOL(percpu_counter_mod);
459 #endif
460 
461 /*
462  * Perform any setup for the swap system
463  */
464 void __init swap_setup(void)
465 {
466 	unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);
467 
468 	/* Use a smaller cluster for small-memory machines */
469 	if (megs < 16)
470 		page_cluster = 2;
471 	else
472 		page_cluster = 3;
473 	/*
474 	 * Right now other parts of the system means that we
475 	 * _really_ don't want to cluster much more
476 	 */
477 	hotcpu_notifier(cpu_swap_callback, 0);
478 }
479