linux/mm/compaction.c
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   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 */
  29struct 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
  47static 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 */
  62static 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 */
 113static 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 */
 138static 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 */
 212static 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 */
 229static 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 */
 247static 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 */
 368static 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 */
 395static 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
 410static 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        /* Compaction run is not finished if the watermark is not met */
 424        watermark = low_wmark_pages(zone);
 425        watermark += (1 << cc->order);
 426
 427        if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0))
 428                return COMPACT_CONTINUE;
 429
 430        /*
 431         * order == -1 is expected when compacting via
 432         * /proc/sys/vm/compact_memory
 433         */
 434        if (cc->order == -1)
 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 */
 458unsigned long compaction_suitable(struct zone *zone, int order)
 459{
 460        int fragindex;
 461        unsigned long watermark;
 462
 463        /*
 464         * Watermarks for order-0 must be met for compaction. Note the 2UL.
 465         * This is because during migration, copies of pages need to be
 466         * allocated and for a short time, the footprint is higher
 467         */
 468        watermark = low_wmark_pages(zone) + (2UL << order);
 469        if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
 470                return COMPACT_SKIPPED;
 471
 472        /*
 473         * order == -1 is expected when compacting via
 474         * /proc/sys/vm/compact_memory
 475         */
 476        if (order == -1)
 477                return COMPACT_CONTINUE;
 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
 499static 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
 557unsigned 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
 575int 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 */
 587unsigned 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 */
 626static 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 */
 664static 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 */
 675int sysctl_compact_memory;
 676
 677/* This is the entry point for compacting all nodes via /proc/sys/vm */
 678int 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
 687int 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)
 696ssize_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}
 704static SYSDEV_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node);
 705
 706int compaction_register_node(struct node *node)
 707{
 708        return sysdev_create_file(&node->sysdev, &attr_compact);
 709}
 710
 711void compaction_unregister_node(struct node *node)
 712{
 713        return sysdev_remove_file(&node->sysdev, &attr_compact);
 714}
 715#endif /* CONFIG_SYSFS && CONFIG_NUMA */
 716