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