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