mm/compaction.c

   1 /*
   2  * linux/mm/compaction.c
   3  *
   4  * Memory compaction for the reduction of external fragmentation. Note that
   5  * this heavily depends upon page migration to do all the real heavy
   6  * lifting
   7  *
   8  * Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie>
   9  */
  10 #include <linux/swap.h>
  11 #include <linux/migrate.h>
  12 #include <linux/compaction.h>
  13 #include <linux/mm_inline.h>
  14 #include <linux/backing-dev.h>
  15 #include <linux/sysctl.h>
  16 #include <linux/sysfs.h>
  17 #include "internal.h"
  18
  19 #define CREATE_TRACE_POINTS
  20 #include <trace/events/compaction.h>
  21
  22 /*
  23  * compact_control is used to track pages being migrated and the free pages
  24  * they are being migrated to during memory compaction. The free_pfn starts
  25  * at the end of a zone and migrate_pfn begins at the start. Movable pages
  26  * are moved to the end of a zone during a compaction run and the run
  27  * completes when free_pfn <= migrate_pfn
  28  */
  29 struct compact_control {
  30         struct list_head freepages;     /* List of free pages to migrate to */
  31         struct list_head migratepages;  /* List of pages being migrated */
  32         unsigned long nr_freepages;     /* Number of isolated free pages */
  33         unsigned long nr_migratepages;  /* Number of pages to migrate */
  34         unsigned long free_pfn;         /* isolate_freepages search base */
  35         unsigned long migrate_pfn;      /* isolate_migratepages search base */
  36         bool sync;                      /* Synchronous migration */
  37
  38         /* Account for isolated anon and file pages */
  39         unsigned long nr_anon;
  40         unsigned long nr_file;
  41
  42         unsigned int order;             /* order a direct compactor needs */
  43         int migratetype;                /* MOVABLE, RECLAIMABLE etc */
  44         struct zone *zone;
  45 };
  46
  47 static unsigned long release_freepages(struct list_head *freelist)
  48 {
  49         struct page *page, *next;
  50         unsigned long count = 0;
  51
  52         list_for_each_entry_safe(page, next, freelist, lru) {
  53                 list_del(&page->lru);
  54                 __free_page(page);
  55                 count++;
  56         }
  57
  58         return count;
  59 }
  60
  61 /* Isolate free pages onto a private freelist. Must hold zone->lock */
  62 static unsigned long isolate_freepages_block(struct zone *zone,
  63                                 unsigned long blockpfn,
  64                                 struct list_head *freelist)
  65 {
  66         unsigned long zone_end_pfn, end_pfn;
  67         int nr_scanned = 0, total_isolated = 0;
  68         struct page *cursor;
  69
  70         /* Get the last PFN we should scan for free pages at */
  71         zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages;
  72         end_pfn = min(blockpfn + pageblock_nr_pages, zone_end_pfn);
  73
  74         /* Find the first usable PFN in the block to initialse page cursor */
  75         for (; blockpfn < end_pfn; blockpfn++) {
  76                 if (pfn_valid_within(blockpfn))
  77                         break;
  78         }
  79         cursor = pfn_to_page(blockpfn);
  80
  81         /* Isolate free pages. This assumes the block is valid */
  82         for (; blockpfn < end_pfn; blockpfn++, cursor++) {
  83                 int isolated, i;
  84                 struct page *page = cursor;
  85
  86                 if (!pfn_valid_within(blockpfn))
  87                         continue;
  88                 nr_scanned++;
  89
  90                 if (!PageBuddy(page))
  91                         continue;
  92
  93                 /* Found a free page, break it into order-0 pages */
  94                 isolated = split_free_page(page);
  95                 total_isolated += isolated;
  96                 for (i = 0; i < isolated; i++) {
  97                         list_add(&page->lru, freelist);
  98                         page++;
  99                 }
 100
 101                 /* If a page was split, advance to the end of it */
 102                 if (isolated) {
 103                         blockpfn += isolated - 1;
 104                         cursor += isolated - 1;
 105                 }
 106         }
 107
 108         trace_mm_compaction_isolate_freepages(nr_scanned, total_isolated);
 109         return total_isolated;
 110 }
 111
 112 /* Returns true if the page is within a block suitable for migration to */
 113 static bool suitable_migration_target(struct page *page)
 114 {
 115
 116         int migratetype = get_pageblock_migratetype(page);
 117
 118         /* Don't interfere with memory hot-remove or the min_free_kbytes blocks */
 119         if (migratetype == MIGRATE_ISOLATE || migratetype == MIGRATE_RESERVE)
 120                 return false;
 121
 122         /* If the page is a large free page, then allow migration */
 123         if (PageBuddy(page) && page_order(page) >= pageblock_order)
 124                 return true;
 125
 126         /* If the block is MIGRATE_MOVABLE, allow migration */
 127         if (migratetype == MIGRATE_MOVABLE)
 128                 return true;
 129
 130         /* Otherwise skip the block */
 131         return false;
 132 }
 133
 134 /*
 135  * Based on information in the current compact_control, find blocks
 136  * suitable for isolating free pages from and then isolate them.
 137  */
 138 static void isolate_freepages(struct zone *zone,
 139                                 struct compact_control *cc)
 140 {
 141         struct page *page;
 142         unsigned long high_pfn, low_pfn, pfn;
 143         unsigned long flags;
 144         int nr_freepages = cc->nr_freepages;
 145         struct list_head *freelist = &cc->freepages;
 146
 147         /*
 148          * Initialise the free scanner. The starting point is where we last
 149          * scanned from (or the end of the zone if starting). The low point
 150          * is the end of the pageblock the migration scanner is using.
 151          */
 152         pfn = cc->free_pfn;
 153         low_pfn = cc->migrate_pfn + pageblock_nr_pages;
 154
 155         /*
 156          * Take care that if the migration scanner is at the end of the zone
 157          * that the free scanner does not accidentally move to the next zone
 158          * in the next isolation cycle.
 159          */
 160         high_pfn = min(low_pfn, pfn);
 161
 162         /*
 163          * Isolate free pages until enough are available to migrate the
 164          * pages on cc->migratepages. We stop searching if the migrate
 165          * and free page scanners meet or enough free pages are isolated.
 166          */
 167         for (; pfn > low_pfn && cc->nr_migratepages > nr_freepages;
 168                                         pfn -= pageblock_nr_pages) {
 169                 unsigned long isolated;
 170
 171                 if (!pfn_valid(pfn))
 172                         continue;
 173
 174                 /*
 175                  * Check for overlapping nodes/zones. It's possible on some
 176                  * configurations to have a setup like
 177                  * node0 node1 node0
 178                  * i.e. it's possible that all pages within a zones range of
 179                  * pages do not belong to a single zone.
 180                  */
 181                 page = pfn_to_page(pfn);
 182                 if (page_zone(page) != zone)
 183                         continue;
 184
 185                 /* Check the block is suitable for migration */
 186                 if (!suitable_migration_target(page))
 187                         continue;
 188
 189                 /*
 190                  * Found a block suitable for isolating free pages from. Now
 191                  * we disabled interrupts, double check things are ok and
 192                  * isolate the pages. This is to minimise the time IRQs
 193                  * are disabled
 194                  */
 195                 isolated = 0;
 196                 spin_lock_irqsave(&zone->lock, flags);
 197                 if (suitable_migration_target(page)) {
 198                         isolated = isolate_freepages_block(zone, pfn, freelist);
 199                         nr_freepages += isolated;
 200                 }
 201                 spin_unlock_irqrestore(&zone->lock, flags);
 202
 203                 /*
 204                  * Record the highest PFN we isolated pages from. When next
 205                  * looking for free pages, the search will restart here as
 206                  * page migration may have returned some pages to the allocator
 207                  */
 208                 if (isolated)
 209                         high_pfn = max(high_pfn, pfn);
 210         }
 211
 212         /* split_free_page does not map the pages */
 213         list_for_each_entry(page, freelist, lru) {
 214                 arch_alloc_page(page, 0);
 215                 kernel_map_pages(page, 1, 1);
 216         }
 217
 218         cc->free_pfn = high_pfn;
 219         cc->nr_freepages = nr_freepages;
 220 }
 221
 222 /* Update the number of anon and file isolated pages in the zone */
 223 static void acct_isolated(struct zone *zone, struct compact_control *cc)
 224 {
 225         struct page *page;
 226         unsigned int count[NR_LRU_LISTS] = { 0, };
 227
 228         list_for_each_entry(page, &cc->migratepages, lru) {
 229                 int lru = page_lru_base_type(page);
 230                 count[lru]++;
 231         }
 232
 233         cc->nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON];
 234         cc->nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE];
 235         __mod_zone_page_state(zone, NR_ISOLATED_ANON, cc->nr_anon);
 236         __mod_zone_page_state(zone, NR_ISOLATED_FILE, cc->nr_file);
 237 }
 238
 239 /* Similar to reclaim, but different enough that they don't share logic */
 240 static bool too_many_isolated(struct zone *zone)
 241 {
 242         unsigned long active, inactive, isolated;
 243
 244         inactive = zone_page_state(zone, NR_INACTIVE_FILE) +
 245                                         zone_page_state(zone, NR_INACTIVE_ANON);
 246         active = zone_page_state(zone, NR_ACTIVE_FILE) +
 247                                         zone_page_state(zone, NR_ACTIVE_ANON);
 248         isolated = zone_page_state(zone, NR_ISOLATED_FILE) +
 249                                         zone_page_state(zone, NR_ISOLATED_ANON);
 250
 251         return isolated > (inactive + active) / 2;
 252 }
 253
 254 /*
 255  * Isolate all pages that can be migrated from the block pointed to by
 256  * the migrate scanner within compact_control.
 257  */
 258 static unsigned long isolate_migratepages(struct zone *zone,
 259                                         struct compact_control *cc)
 260 {
 261         unsigned long low_pfn, end_pfn;
 262         unsigned long last_pageblock_nr = 0, pageblock_nr;
 263         unsigned long nr_scanned = 0, nr_isolated = 0;
 264         struct list_head *migratelist = &cc->migratepages;
 265
 266         /* Do not scan outside zone boundaries */
 267         low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
 268
 269         /* Only scan within a pageblock boundary */
 270         end_pfn = ALIGN(low_pfn + pageblock_nr_pages, pageblock_nr_pages);
 271
 272         /* Do not cross the free scanner or scan within a memory hole */
 273         if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) {
 274                 cc->migrate_pfn = end_pfn;
 275                 return 0;
 276         }
 277
 278         /*
 279          * Ensure that there are not too many pages isolated from the LRU
 280          * list by either parallel reclaimers or compaction. If there are,
 281          * delay for some time until fewer pages are isolated
 282          */
 283         while (unlikely(too_many_isolated(zone))) {
 284                 congestion_wait(BLK_RW_ASYNC, HZ/10);
 285
 286                 if (fatal_signal_pending(current))
 287                         return 0;
 288         }
 289
 290         /* Time to isolate some pages for migration */
 291         cond_resched();
 292         spin_lock_irq(&zone->lru_lock);
 293         for (; low_pfn < end_pfn; low_pfn++) {
 294                 struct page *page;
 295                 bool locked = true;
 296
 297                 /* give a chance to irqs before checking need_resched() */
 298                 if (!((low_pfn+1) % SWAP_CLUSTER_MAX)) {
 299                         spin_unlock_irq(&zone->lru_lock);
 300                         locked = false;
 301                 }
 302                 if (need_resched() || spin_is_contended(&zone->lru_lock)) {
 303                         if (locked)
 304                                 spin_unlock_irq(&zone->lru_lock);
 305                         cond_resched();
 306                         spin_lock_irq(&zone->lru_lock);
 307                         if (fatal_signal_pending(current))
 308                                 break;
 309                 } else if (!locked)
 310                         spin_lock_irq(&zone->lru_lock);
 311
 312                 if (!pfn_valid_within(low_pfn))
 313                         continue;
 314                 nr_scanned++;
 315
 316                 /* Get the page and skip if free */
 317                 page = pfn_to_page(low_pfn);
 318                 if (PageBuddy(page))
 319                         continue;
 320
 321                 /*
 322                  * For async migration, also only scan in MOVABLE blocks. Async
 323                  * migration is optimistic to see if the minimum amount of work
 324                  * satisfies the allocation
 325                  */
 326                 pageblock_nr = low_pfn >> pageblock_order;
 327                 if (!cc->sync && last_pageblock_nr != pageblock_nr &&
 328                                 get_pageblock_migratetype(page) != MIGRATE_MOVABLE) {
 329                         low_pfn += pageblock_nr_pages;
 330                         low_pfn = ALIGN(low_pfn, pageblock_nr_pages) - 1;
 331                         last_pageblock_nr = pageblock_nr;
 332                         continue;
 333                 }
 334
 335                 if (!PageLRU(page))
 336                         continue;
 337
 338                 /*
 339                  * PageLRU is set, and lru_lock excludes isolation,
 340                  * splitting and collapsing (collapsing has already
 341                  * happened if PageLRU is set).
 342                  */
 343                 if (PageTransHuge(page)) {
 344                         low_pfn += (1 << compound_order(page)) - 1;
 345                         continue;
 346                 }
 347
 348                 /* Try isolate the page */
 349                 if (__isolate_lru_page(page, ISOLATE_BOTH, 0) != 0)
 350                         continue;
 351
 352                 VM_BUG_ON(PageTransCompound(page));
 353
 354                 /* Successfully isolated */
 355                 del_page_from_lru_list(zone, page, page_lru(page));
 356                 list_add(&page->lru, migratelist);
 357                 cc->nr_migratepages++;
 358                 nr_isolated++;
 359
 360                 /* Avoid isolating too much */
 361                 if (cc->nr_migratepages == COMPACT_CLUSTER_MAX)
 362                         break;
 363         }
 364
 365         acct_isolated(zone, cc);
 366
 367         spin_unlock_irq(&zone->lru_lock);
 368         cc->migrate_pfn = low_pfn;
 369
 370         trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated);
 371
 372         return cc->nr_migratepages;
 373 }
 374
 375 /*
 376  * This is a migrate-callback that "allocates" freepages by taking pages
 377  * from the isolated freelists in the block we are migrating to.
 378  */
 379 static struct page *compaction_alloc(struct page *migratepage,
 380                                         unsigned long data,
 381                                         int **result)
 382 {
 383         struct compact_control *cc = (struct compact_control *)data;
 384         struct page *freepage;
 385
 386         /* Isolate free pages if necessary */
 387         if (list_empty(&cc->freepages)) {
 388                 isolate_freepages(cc->zone, cc);
 389
 390                 if (list_empty(&cc->freepages))
 391                         return NULL;
 392         }
 393
 394         freepage = list_entry(cc->freepages.next, struct page, lru);
 395         list_del(&freepage->lru);
 396         cc->nr_freepages--;
 397
 398         return freepage;
 399 }
 400
 401 /*
 402  * We cannot control nr_migratepages and nr_freepages fully when migration is
 403  * running as migrate_pages() has no knowledge of compact_control. When
 404  * migration is complete, we count the number of pages on the lists by hand.
 405  */
 406 static void update_nr_listpages(struct compact_control *cc)
 407 {
 408         int nr_migratepages = 0;
 409         int nr_freepages = 0;
 410         struct page *page;
 411
 412         list_for_each_entry(page, &cc->migratepages, lru)
 413                 nr_migratepages++;
 414         list_for_each_entry(page, &cc->freepages, lru)
 415                 nr_freepages++;
 416
 417         cc->nr_migratepages = nr_migratepages;
 418         cc->nr_freepages = nr_freepages;
 419 }
 420
 421 static int compact_finished(struct zone *zone,
 422                             struct compact_control *cc)
 423 {
 424         unsigned int order;
 425         unsigned long watermark;
 426
 427         if (fatal_signal_pending(current))
 428                 return COMPACT_PARTIAL;
 429
 430         /* Compaction run completes if the migrate and free scanner meet */
 431         if (cc->free_pfn <= cc->migrate_pfn)
 432                 return COMPACT_COMPLETE;
 433
 434         /*
 435          * order == -1 is expected when compacting via
 436          * /proc/sys/vm/compact_memory
 437          */
 438         if (cc->order == -1)
 439                 return COMPACT_CONTINUE;
 440
 441         /* Compaction run is not finished if the watermark is not met */
 442         watermark = low_wmark_pages(zone);
 443         watermark += (1 << cc->order);
 444
 445         if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0))
 446                 return COMPACT_CONTINUE;
 447
 448         /* Direct compactor: Is a suitable page free? */
 449         for (order = cc->order; order < MAX_ORDER; order++) {
 450                 /* Job done if page is free of the right migratetype */
 451                 if (!list_empty(&zone->free_area[order].free_list[cc->migratetype]))
 452                         return COMPACT_PARTIAL;
 453
 454                 /* Job done if allocation would set block type */
 455                 if (order >= pageblock_order && zone->free_area[order].nr_free)
 456                         return COMPACT_PARTIAL;
 457         }
 458
 459         return COMPACT_CONTINUE;
 460 }
 461
 462 /*
 463  * compaction_suitable: Is this suitable to run compaction on this zone now?
 464  * Returns
 465  *   COMPACT_SKIPPED  - If there are too few free pages for compaction
 466  *   COMPACT_PARTIAL  - If the allocation would succeed without compaction
 467  *   COMPACT_CONTINUE - If compaction should run now
 468  */
 469 unsigned long compaction_suitable(struct zone *zone, int order)
 470 {
 471         int fragindex;
 472         unsigned long watermark;
 473
 474         /*
 475          * order == -1 is expected when compacting via
 476          * /proc/sys/vm/compact_memory
 477          */
 478         if (order == -1)
 479                 return COMPACT_CONTINUE;
 480
 481         /*
 482          * Watermarks for order-0 must be met for compaction. Note the 2UL.
 483          * This is because during migration, copies of pages need to be
 484          * allocated and for a short time, the footprint is higher
 485          */
 486         watermark = low_wmark_pages(zone) + (2UL << order);
 487         if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
 488                 return COMPACT_SKIPPED;
 489
 490         /*
 491          * fragmentation index determines if allocation failures are due to
 492          * low memory or external fragmentation
 493          *
 494          * index of -1000 implies allocations might succeed depending on
 495          * watermarks
 496          * index towards 0 implies failure is due to lack of memory
 497          * index towards 1000 implies failure is due to fragmentation
 498          *
 499          * Only compact if a failure would be due to fragmentation.
 500          */
 501         fragindex = fragmentation_index(zone, order);
 502         if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
 503                 return COMPACT_SKIPPED;
 504
 505         if (fragindex == -1000 && zone_watermark_ok(zone, order, watermark,
 506             0, 0))
 507                 return COMPACT_PARTIAL;
 508
 509         return COMPACT_CONTINUE;
 510 }
 511
 512 static int compact_zone(struct zone *zone, struct compact_control *cc)
 513 {
 514         int ret;
 515
 516         ret = compaction_suitable(zone, cc->order);
 517         switch (ret) {
 518         case COMPACT_PARTIAL:
 519         case COMPACT_SKIPPED:
 520                 /* Compaction is likely to fail */
 521                 return ret;
 522         case COMPACT_CONTINUE:
 523                 /* Fall through to compaction */
 524                 ;
 525         }
 526
 527         /* Setup to move all movable pages to the end of the zone */
 528         cc->migrate_pfn = zone->zone_start_pfn;
 529         cc->free_pfn = cc->migrate_pfn + zone->spanned_pages;
 530         cc->free_pfn &= ~(pageblock_nr_pages-1);
 531
 532         migrate_prep_local();
 533
 534         while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) {
 535                 unsigned long nr_migrate, nr_remaining;
 536                 int err;
 537
 538                 if (!isolate_migratepages(zone, cc))
 539                         continue;
 540
 541                 nr_migrate = cc->nr_migratepages;
 542                 err = migrate_pages(&cc->migratepages, compaction_alloc,
 543                                 (unsigned long)cc, false,
 544                                 cc->sync);
 545                 update_nr_listpages(cc);
 546                 nr_remaining = cc->nr_migratepages;
 547
 548                 count_vm_event(COMPACTBLOCKS);
 549                 count_vm_events(COMPACTPAGES, nr_migrate - nr_remaining);
 550                 if (nr_remaining)
 551                         count_vm_events(COMPACTPAGEFAILED, nr_remaining);
 552                 trace_mm_compaction_migratepages(nr_migrate - nr_remaining,
 553                                                 nr_remaining);
 554
 555                 /* Release LRU pages not migrated */
 556                 if (err) {
 557                         putback_lru_pages(&cc->migratepages);
 558                         cc->nr_migratepages = 0;
 559                 }
 560
 561         }
 562
 563         /* Release free pages and check accounting */
 564         cc->nr_freepages -= release_freepages(&cc->freepages);
 565         VM_BUG_ON(cc->nr_freepages != 0);
 566
 567         return ret;
 568 }
 569
 570 unsigned long compact_zone_order(struct zone *zone,
 571                                  int order, gfp_t gfp_mask,
 572                                  bool sync)
 573 {
 574         struct compact_control cc = {
 575                 .nr_freepages = 0,
 576                 .nr_migratepages = 0,
 577                 .order = order,
 578                 .migratetype = allocflags_to_migratetype(gfp_mask),
 579                 .zone = zone,
 580                 .sync = sync,
 581         };
 582         INIT_LIST_HEAD(&cc.freepages);
 583         INIT_LIST_HEAD(&cc.migratepages);
 584
 585         return compact_zone(zone, &cc);
 586 }
 587
 588 int sysctl_extfrag_threshold = 500;
 589
 590 /**
 591  * try_to_compact_pages - Direct compact to satisfy a high-order allocation
 592  * @zonelist: The zonelist used for the current allocation
 593  * @order: The order of the current allocation
 594  * @gfp_mask: The GFP mask of the current allocation
 595  * @nodemask: The allowed nodes to allocate from
 596  * @sync: Whether migration is synchronous or not
 597  *
 598  * This is the main entry point for direct page compaction.
 599  */
 600 unsigned long try_to_compact_pages(struct zonelist *zonelist,
 601                         int order, gfp_t gfp_mask, nodemask_t *nodemask,
 602                         bool sync)
 603 {
 604         enum zone_type high_zoneidx = gfp_zone(gfp_mask);
 605         int may_enter_fs = gfp_mask & __GFP_FS;
 606         int may_perform_io = gfp_mask & __GFP_IO;
 607         struct zoneref *z;
 608         struct zone *zone;
 609         int rc = COMPACT_SKIPPED;
 610
 611         /*
 612          * Check whether it is worth even starting compaction. The order check is
 613          * made because an assumption is made that the page allocator can satisfy
 614          * the "cheaper" orders without taking special steps
 615          */
 616         if (!order || !may_enter_fs || !may_perform_io)
 617                 return rc;
 618
 619         count_vm_event(COMPACTSTALL);
 620
 621         /* Compact each zone in the list */
 622         for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
 623                                                                 nodemask) {
 624                 int status;
 625
 626                 status = compact_zone_order(zone, order, gfp_mask, sync);
 627                 rc = max(status, rc);
 628
 629                 /* If a normal allocation would succeed, stop compacting */
 630                 if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0))
 631                         break;
 632         }
 633
 634         return rc;
 635 }
 636
 637
 638 /* Compact all zones within a node */
 639 static int compact_node(int nid)
 640 {
 641         int zoneid;
 642         pg_data_t *pgdat;
 643         struct zone *zone;
 644
 645         if (nid < 0 || nid >= nr_node_ids || !node_online(nid))
 646                 return -EINVAL;
 647         pgdat = NODE_DATA(nid);
 648
 649         /* Flush pending updates to the LRU lists */
 650         lru_add_drain_all();
 651
 652         for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
 653                 struct compact_control cc = {
 654                         .nr_freepages = 0,
 655                         .nr_migratepages = 0,
 656                         .order = -1,
 657                 };
 658
 659                 zone = &pgdat->node_zones[zoneid];
 660                 if (!populated_zone(zone))
 661                         continue;
 662
 663                 cc.zone = zone;
 664                 INIT_LIST_HEAD(&cc.freepages);
 665                 INIT_LIST_HEAD(&cc.migratepages);
 666
 667                 compact_zone(zone, &cc);
 668
 669                 VM_BUG_ON(!list_empty(&cc.freepages));
 670                 VM_BUG_ON(!list_empty(&cc.migratepages));
 671         }
 672
 673         return 0;
 674 }
 675
 676 /* Compact all nodes in the system */
 677 static int compact_nodes(void)
 678 {
 679         int nid;
 680
 681         for_each_online_node(nid)
 682                 compact_node(nid);
 683
 684         return COMPACT_COMPLETE;
 685 }
 686
 687 /* The written value is actually unused, all memory is compacted */
 688 int sysctl_compact_memory;
 689
 690 /* This is the entry point for compacting all nodes via /proc/sys/vm */
 691 int sysctl_compaction_handler(struct ctl_table *table, int write,
 692                         void __user *buffer, size_t *length, loff_t *ppos)
 693 {
 694         if (write)
 695                 return compact_nodes();
 696
 697         return 0;
 698 }
 699
 700 int sysctl_extfrag_handler(struct ctl_table *table, int write,
 701                         void __user *buffer, size_t *length, loff_t *ppos)
 702 {
 703         proc_dointvec_minmax(table, write, buffer, length, ppos);
 704
 705         return 0;
 706 }
 707
 708 #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
 709 ssize_t sysfs_compact_node(struct sys_device *dev,
 710                         struct sysdev_attribute *attr,
 711                         const char *buf, size_t count)
 712 {
 713         compact_node(dev->id);
 714
 715         return count;
 716 }
 717 static SYSDEV_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node);
 718
 719 int compaction_register_node(struct node *node)
 720 {
 721         return sysdev_create_file(&node->sysdev, &attr_compact);
 722 }
 723
 724 void compaction_unregister_node(struct node *node)
 725 {
 726         return sysdev_remove_file(&node->sysdev, &attr_compact);
 727 }
 728 #endif /* CONFIG_SYSFS && CONFIG_NUMA */