mm/swap.c

   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 static void put_compound_page(struct page *page)
  38 {
  39         page = (struct page *)page_private(page);
  40         if (put_page_testzero(page)) {
  41                 void (*dtor)(struct page *page);
  42
  43                 dtor = (void (*)(struct page *))page[1].lru.next;
  44                 (*dtor)(page);
  45         }
  46 }
  47
  48 void put_page(struct page *page)
  49 {
  50         if (unlikely(PageCompound(page)))
  51                 put_compound_page(page);
  52         else if (put_page_testzero(page))
  53                 __page_cache_release(page);
  54 }
  55 EXPORT_SYMBOL(put_page);
  56
  57 /*
  58  * Writeback is about to end against a page which has been marked for immediate
  59  * reclaim.  If it still appears to be reclaimable, move it to the tail of the
  60  * inactive list.  The page still has PageWriteback set, which will pin it.
  61  *
  62  * We don't expect many pages to come through here, so don't bother batching
  63  * things up.
  64  *
  65  * To avoid placing the page at the tail of the LRU while PG_writeback is still
  66  * set, this function will clear PG_writeback before performing the page
  67  * motion.  Do that inside the lru lock because once PG_writeback is cleared
  68  * we may not touch the page.
  69  *
  70  * Returns zero if it cleared PG_writeback.
  71  */
  72 int rotate_reclaimable_page(struct page *page)
  73 {
  74         struct zone *zone;
  75         unsigned long flags;
  76
  77         if (PageLocked(page))
  78                 return 1;
  79         if (PageDirty(page))
  80                 return 1;
  81         if (PageActive(page))
  82                 return 1;
  83         if (!PageLRU(page))
  84                 return 1;
  85
  86         zone = page_zone(page);
  87         spin_lock_irqsave(&zone->lru_lock, flags);
  88         if (PageLRU(page) && !PageActive(page)) {
  89                 list_move_tail(&page->lru, &zone->inactive_list);
  90                 __count_vm_event(PGROTATED);
  91         }
  92         if (!test_clear_page_writeback(page))
  93                 BUG();
  94         spin_unlock_irqrestore(&zone->lru_lock, flags);
  95         return 0;
  96 }
  97
  98 /*
  99  * FIXME: speed this up?
 100  */
 101 void fastcall activate_page(struct page *page)
 102 {
 103         struct zone *zone = page_zone(page);
 104
 105         spin_lock_irq(&zone->lru_lock);
 106         if (PageLRU(page) && !PageActive(page)) {
 107                 del_page_from_inactive_list(zone, page);
 108                 SetPageActive(page);
 109                 add_page_to_active_list(zone, page);
 110                 __count_vm_event(PGACTIVATE);
 111         }
 112         spin_unlock_irq(&zone->lru_lock);
 113 }
 114
 115 /*
 116  * Mark a page as having seen activity.
 117  *
 118  * inactive,unreferenced        ->      inactive,referenced
 119  * inactive,referenced          ->      active,unreferenced
 120  * active,unreferenced          ->      active,referenced
 121  */
 122 void fastcall mark_page_accessed(struct page *page)
 123 {
 124         if (!PageActive(page) && PageReferenced(page) && PageLRU(page)) {
 125                 activate_page(page);
 126                 ClearPageReferenced(page);
 127         } else if (!PageReferenced(page)) {
 128                 SetPageReferenced(page);
 129         }
 130 }
 131
 132 EXPORT_SYMBOL(mark_page_accessed);
 133
 134 /**
 135  * lru_cache_add: add a page to the page lists
 136  * @page: the page to add
 137  */
 138 static DEFINE_PER_CPU(struct pagevec, lru_add_pvecs) = { 0, };
 139 static DEFINE_PER_CPU(struct pagevec, lru_add_active_pvecs) = { 0, };
 140
 141 void fastcall lru_cache_add(struct page *page)
 142 {
 143         struct pagevec *pvec = &get_cpu_var(lru_add_pvecs);
 144
 145         page_cache_get(page);
 146         if (!pagevec_add(pvec, page))
 147                 __pagevec_lru_add(pvec);
 148         put_cpu_var(lru_add_pvecs);
 149 }
 150
 151 void fastcall lru_cache_add_active(struct page *page)
 152 {
 153         struct pagevec *pvec = &get_cpu_var(lru_add_active_pvecs);
 154
 155         page_cache_get(page);
 156         if (!pagevec_add(pvec, page))
 157                 __pagevec_lru_add_active(pvec);
 158         put_cpu_var(lru_add_active_pvecs);
 159 }
 160
 161 static void __lru_add_drain(int cpu)
 162 {
 163         struct pagevec *pvec = &per_cpu(lru_add_pvecs, cpu);
 164
 165         /* CPU is dead, so no locking needed. */
 166         if (pagevec_count(pvec))
 167                 __pagevec_lru_add(pvec);
 168         pvec = &per_cpu(lru_add_active_pvecs, cpu);
 169         if (pagevec_count(pvec))
 170                 __pagevec_lru_add_active(pvec);
 171 }
 172
 173 void lru_add_drain(void)
 174 {
 175         __lru_add_drain(get_cpu());
 176         put_cpu();
 177 }
 178
 179 #ifdef CONFIG_NUMA
 180 static void lru_add_drain_per_cpu(void *dummy)
 181 {
 182         lru_add_drain();
 183 }
 184
 185 /*
 186  * Returns 0 for success
 187  */
 188 int lru_add_drain_all(void)
 189 {
 190         return schedule_on_each_cpu(lru_add_drain_per_cpu, NULL);
 191 }
 192
 193 #else
 194
 195 /*
 196  * Returns 0 for success
 197  */
 198 int lru_add_drain_all(void)
 199 {
 200         lru_add_drain();
 201         return 0;
 202 }
 203 #endif
 204
 205 /*
 206  * This path almost never happens for VM activity - pages are normally
 207  * freed via pagevecs.  But it gets used by networking.
 208  */
 209 void fastcall __page_cache_release(struct page *page)
 210 {
 211         if (PageLRU(page)) {
 212                 unsigned long flags;
 213                 struct zone *zone = page_zone(page);
 214
 215                 spin_lock_irqsave(&zone->lru_lock, flags);
 216                 BUG_ON(!PageLRU(page));
 217                 __ClearPageLRU(page);
 218                 del_page_from_lru(zone, page);
 219                 spin_unlock_irqrestore(&zone->lru_lock, flags);
 220         }
 221         free_hot_page(page);
 222 }
 223 EXPORT_SYMBOL(__page_cache_release);
 224
 225 /*
 226  * Batched page_cache_release().  Decrement the reference count on all the
 227  * passed pages.  If it fell to zero then remove the page from the LRU and
 228  * free it.
 229  *
 230  * Avoid taking zone->lru_lock if possible, but if it is taken, retain it
 231  * for the remainder of the operation.
 232  *
 233  * The locking in this function is against shrink_cache(): we recheck the
 234  * page count inside the lock to see whether shrink_cache grabbed the page
 235  * via the LRU.  If it did, give up: shrink_cache will free it.
 236  */
 237 void release_pages(struct page **pages, int nr, int cold)
 238 {
 239         int i;
 240         struct pagevec pages_to_free;
 241         struct zone *zone = NULL;
 242
 243         pagevec_init(&pages_to_free, cold);
 244         for (i = 0; i < nr; i++) {
 245                 struct page *page = pages[i];
 246
 247                 if (unlikely(PageCompound(page))) {
 248                         if (zone) {
 249                                 spin_unlock_irq(&zone->lru_lock);
 250                                 zone = NULL;
 251                         }
 252                         put_compound_page(page);
 253                         continue;
 254                 }
 255
 256                 if (!put_page_testzero(page))
 257                         continue;
 258
 259                 if (PageLRU(page)) {
 260                         struct zone *pagezone = page_zone(page);
 261                         if (pagezone != zone) {
 262                                 if (zone)
 263                                         spin_unlock_irq(&zone->lru_lock);
 264                                 zone = pagezone;
 265                                 spin_lock_irq(&zone->lru_lock);
 266                         }
 267                         BUG_ON(!PageLRU(page));
 268                         __ClearPageLRU(page);
 269                         del_page_from_lru(zone, page);
 270                 }
 271
 272                 if (!pagevec_add(&pages_to_free, page)) {
 273                         if (zone) {
 274                                 spin_unlock_irq(&zone->lru_lock);
 275                                 zone = NULL;
 276                         }
 277                         __pagevec_free(&pages_to_free);
 278                         pagevec_reinit(&pages_to_free);
 279                 }
 280         }
 281         if (zone)
 282                 spin_unlock_irq(&zone->lru_lock);
 283
 284         pagevec_free(&pages_to_free);
 285 }
 286
 287 /*
 288  * The pages which we're about to release may be in the deferred lru-addition
 289  * queues.  That would prevent them from really being freed right now.  That's
 290  * OK from a correctness point of view but is inefficient - those pages may be
 291  * cache-warm and we want to give them back to the page allocator ASAP.
 292  *
 293  * So __pagevec_release() will drain those queues here.  __pagevec_lru_add()
 294  * and __pagevec_lru_add_active() call release_pages() directly to avoid
 295  * mutual recursion.
 296  */
 297 void __pagevec_release(struct pagevec *pvec)
 298 {
 299         lru_add_drain();
 300         release_pages(pvec->pages, pagevec_count(pvec), pvec->cold);
 301         pagevec_reinit(pvec);
 302 }
 303
 304 EXPORT_SYMBOL(__pagevec_release);
 305
 306 /*
 307  * pagevec_release() for pages which are known to not be on the LRU
 308  *
 309  * This function reinitialises the caller's pagevec.
 310  */
 311 void __pagevec_release_nonlru(struct pagevec *pvec)
 312 {
 313         int i;
 314         struct pagevec pages_to_free;
 315
 316         pagevec_init(&pages_to_free, pvec->cold);
 317         for (i = 0; i < pagevec_count(pvec); i++) {
 318                 struct page *page = pvec->pages[i];
 319
 320                 BUG_ON(PageLRU(page));
 321                 if (put_page_testzero(page))
 322                         pagevec_add(&pages_to_free, page);
 323         }
 324         pagevec_free(&pages_to_free);
 325         pagevec_reinit(pvec);
 326 }
 327
 328 /*
 329  * Add the passed pages to the LRU, then drop the caller's refcount
 330  * on them.  Reinitialises the caller's pagevec.
 331  */
 332 void __pagevec_lru_add(struct pagevec *pvec)
 333 {
 334         int i;
 335         struct zone *zone = NULL;
 336
 337         for (i = 0; i < pagevec_count(pvec); i++) {
 338                 struct page *page = pvec->pages[i];
 339                 struct zone *pagezone = page_zone(page);
 340
 341                 if (pagezone != zone) {
 342                         if (zone)
 343                                 spin_unlock_irq(&zone->lru_lock);
 344                         zone = pagezone;
 345                         spin_lock_irq(&zone->lru_lock);
 346                 }
 347                 BUG_ON(PageLRU(page));
 348                 SetPageLRU(page);
 349                 add_page_to_inactive_list(zone, page);
 350         }
 351         if (zone)
 352                 spin_unlock_irq(&zone->lru_lock);
 353         release_pages(pvec->pages, pvec->nr, pvec->cold);
 354         pagevec_reinit(pvec);
 355 }
 356
 357 EXPORT_SYMBOL(__pagevec_lru_add);
 358
 359 void __pagevec_lru_add_active(struct pagevec *pvec)
 360 {
 361         int i;
 362         struct zone *zone = NULL;
 363
 364         for (i = 0; i < pagevec_count(pvec); i++) {
 365                 struct page *page = pvec->pages[i];
 366                 struct zone *pagezone = page_zone(page);
 367
 368                 if (pagezone != zone) {
 369                         if (zone)
 370                                 spin_unlock_irq(&zone->lru_lock);
 371                         zone = pagezone;
 372                         spin_lock_irq(&zone->lru_lock);
 373                 }
 374                 BUG_ON(PageLRU(page));
 375                 SetPageLRU(page);
 376                 BUG_ON(PageActive(page));
 377                 SetPageActive(page);
 378                 add_page_to_active_list(zone, page);
 379         }
 380         if (zone)
 381                 spin_unlock_irq(&zone->lru_lock);
 382         release_pages(pvec->pages, pvec->nr, pvec->cold);
 383         pagevec_reinit(pvec);
 384 }
 385
 386 /*
 387  * Try to drop buffers from the pages in a pagevec
 388  */
 389 void pagevec_strip(struct pagevec *pvec)
 390 {
 391         int i;
 392
 393         for (i = 0; i < pagevec_count(pvec); i++) {
 394                 struct page *page = pvec->pages[i];
 395
 396                 if (PagePrivate(page) && !TestSetPageLocked(page)) {
 397                         if (PagePrivate(page))
 398                                 try_to_release_page(page, 0);
 399                         unlock_page(page);
 400                 }
 401         }
 402 }
 403
 404 /**
 405  * pagevec_lookup - gang pagecache lookup
 406  * @pvec:       Where the resulting pages are placed
 407  * @mapping:    The address_space to search
 408  * @start:      The starting page index
 409  * @nr_pages:   The maximum number of pages
 410  *
 411  * pagevec_lookup() will search for and return a group of up to @nr_pages pages
 412  * in the mapping.  The pages are placed in @pvec.  pagevec_lookup() takes a
 413  * reference against the pages in @pvec.
 414  *
 415  * The search returns a group of mapping-contiguous pages with ascending
 416  * indexes.  There may be holes in the indices due to not-present pages.
 417  *
 418  * pagevec_lookup() returns the number of pages which were found.
 419  */
 420 unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
 421                 pgoff_t start, unsigned nr_pages)
 422 {
 423         pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
 424         return pagevec_count(pvec);
 425 }
 426
 427 EXPORT_SYMBOL(pagevec_lookup);
 428
 429 unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
 430                 pgoff_t *index, int tag, unsigned nr_pages)
 431 {
 432         pvec->nr = find_get_pages_tag(mapping, index, tag,
 433                                         nr_pages, pvec->pages);
 434         return pagevec_count(pvec);
 435 }
 436
 437 EXPORT_SYMBOL(pagevec_lookup_tag);
 438
 439 #ifdef CONFIG_SMP
 440 /*
 441  * We tolerate a little inaccuracy to avoid ping-ponging the counter between
 442  * CPUs
 443  */
 444 #define ACCT_THRESHOLD  max(16, NR_CPUS * 2)
 445
 446 static DEFINE_PER_CPU(long, committed_space) = 0;
 447
 448 void vm_acct_memory(long pages)
 449 {
 450         long *local;
 451
 452         preempt_disable();
 453         local = &__get_cpu_var(committed_space);
 454         *local += pages;
 455         if (*local > ACCT_THRESHOLD || *local < -ACCT_THRESHOLD) {
 456                 atomic_add(*local, &vm_committed_space);
 457                 *local = 0;
 458         }
 459         preempt_enable();
 460 }
 461
 462 #ifdef CONFIG_HOTPLUG_CPU
 463
 464 /* Drop the CPU's cached committed space back into the central pool. */
 465 static int cpu_swap_callback(struct notifier_block *nfb,
 466                              unsigned long action,
 467                              void *hcpu)
 468 {
 469         long *committed;
 470
 471         committed = &per_cpu(committed_space, (long)hcpu);
 472         if (action == CPU_DEAD) {
 473                 atomic_add(*committed, &vm_committed_space);
 474                 *committed = 0;
 475                 __lru_add_drain((long)hcpu);
 476         }
 477         return NOTIFY_OK;
 478 }
 479 #endif /* CONFIG_HOTPLUG_CPU */
 480 #endif /* CONFIG_SMP */
 481
 482 /*
 483  * Perform any setup for the swap system
 484  */
 485 void __init swap_setup(void)
 486 {
 487         unsigned long megs = num_physpages >> (20 - PAGE_SHIFT);
 488
 489         /* Use a smaller cluster for small-memory machines */
 490         if (megs < 16)
 491                 page_cluster = 2;
 492         else
 493                 page_cluster = 3;
 494         /*
 495          * Right now other parts of the system means that we
 496          * _really_ don't want to cluster much more
 497          */
 498         hotcpu_notifier(cpu_swap_callback, 0);
 499 }