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        /*
 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 */
 223static 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 */
 240static 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/* possible outcome of isolate_migratepages */
 255typedef enum {
 256        ISOLATE_ABORT,          /* Abort compaction now */
 257        ISOLATE_NONE,           /* No pages isolated, continue scanning */
 258        ISOLATE_SUCCESS,        /* Pages isolated, migrate */
 259} isolate_migrate_t;
 260
 261/*
 262 * Isolate all pages that can be migrated from the block pointed to by
 263 * the migrate scanner within compact_control.
 264 */
 265static isolate_migrate_t isolate_migratepages(struct zone *zone,
 266                                        struct compact_control *cc)
 267{
 268        unsigned long low_pfn, end_pfn;
 269        unsigned long last_pageblock_nr = 0, pageblock_nr;
 270        unsigned long nr_scanned = 0, nr_isolated = 0;
 271        struct list_head *migratelist = &cc->migratepages;
 272
 273        /* Do not scan outside zone boundaries */
 274        low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn);
 275
 276        /* Only scan within a pageblock boundary */
 277        end_pfn = ALIGN(low_pfn + pageblock_nr_pages, pageblock_nr_pages);
 278
 279        /* Do not cross the free scanner or scan within a memory hole */
 280        if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) {
 281                cc->migrate_pfn = end_pfn;
 282                return ISOLATE_NONE;
 283        }
 284
 285        /*
 286         * Ensure that there are not too many pages isolated from the LRU
 287         * list by either parallel reclaimers or compaction. If there are,
 288         * delay for some time until fewer pages are isolated
 289         */
 290        while (unlikely(too_many_isolated(zone))) {
 291                /* async migration should just abort */
 292                if (!cc->sync)
 293                        return ISOLATE_ABORT;
 294
 295                congestion_wait(BLK_RW_ASYNC, HZ/10);
 296
 297                if (fatal_signal_pending(current))
 298                        return ISOLATE_ABORT;
 299        }
 300
 301        /* Time to isolate some pages for migration */
 302        cond_resched();
 303        spin_lock_irq(&zone->lru_lock);
 304        for (; low_pfn < end_pfn; low_pfn++) {
 305                struct page *page;
 306                bool locked = true;
 307
 308                /* give a chance to irqs before checking need_resched() */
 309                if (!((low_pfn+1) % SWAP_CLUSTER_MAX)) {
 310                        spin_unlock_irq(&zone->lru_lock);
 311                        locked = false;
 312                }
 313                if (need_resched() || spin_is_contended(&zone->lru_lock)) {
 314                        if (locked)
 315                                spin_unlock_irq(&zone->lru_lock);
 316                        cond_resched();
 317                        spin_lock_irq(&zone->lru_lock);
 318                        if (fatal_signal_pending(current))
 319                                break;
 320                } else if (!locked)
 321                        spin_lock_irq(&zone->lru_lock);
 322
 323                if (!pfn_valid_within(low_pfn))
 324                        continue;
 325                nr_scanned++;
 326
 327                /* Get the page and skip if free */
 328                page = pfn_to_page(low_pfn);
 329                if (PageBuddy(page))
 330                        continue;
 331
 332                /*
 333                 * For async migration, also only scan in MOVABLE blocks. Async
 334                 * migration is optimistic to see if the minimum amount of work
 335                 * satisfies the allocation
 336                 */
 337                pageblock_nr = low_pfn >> pageblock_order;
 338                if (!cc->sync && last_pageblock_nr != pageblock_nr &&
 339                                get_pageblock_migratetype(page) != MIGRATE_MOVABLE) {
 340                        low_pfn += pageblock_nr_pages;
 341                        low_pfn = ALIGN(low_pfn, pageblock_nr_pages) - 1;
 342                        last_pageblock_nr = pageblock_nr;
 343                        continue;
 344                }
 345
 346                if (!PageLRU(page))
 347                        continue;
 348
 349                /*
 350                 * PageLRU is set, and lru_lock excludes isolation,
 351                 * splitting and collapsing (collapsing has already
 352                 * happened if PageLRU is set).
 353                 */
 354                if (PageTransHuge(page)) {
 355                        low_pfn += (1 << compound_order(page)) - 1;
 356                        continue;
 357                }
 358
 359                /* Try isolate the page */
 360                if (__isolate_lru_page(page, ISOLATE_BOTH, 0) != 0)
 361                        continue;
 362
 363                VM_BUG_ON(PageTransCompound(page));
 364
 365                /* Successfully isolated */
 366                del_page_from_lru_list(zone, page, page_lru(page));
 367                list_add(&page->lru, migratelist);
 368                cc->nr_migratepages++;
 369                nr_isolated++;
 370
 371                /* Avoid isolating too much */
 372                if (cc->nr_migratepages == COMPACT_CLUSTER_MAX)
 373                        break;
 374        }
 375
 376        acct_isolated(zone, cc);
 377
 378        spin_unlock_irq(&zone->lru_lock);
 379        cc->migrate_pfn = low_pfn;
 380
 381        trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated);
 382
 383        return ISOLATE_SUCCESS;
 384}
 385
 386/*
 387 * This is a migrate-callback that "allocates" freepages by taking pages
 388 * from the isolated freelists in the block we are migrating to.
 389 */
 390static struct page *compaction_alloc(struct page *migratepage,
 391                                        unsigned long data,
 392                                        int **result)
 393{
 394        struct compact_control *cc = (struct compact_control *)data;
 395        struct page *freepage;
 396
 397        /* Isolate free pages if necessary */
 398        if (list_empty(&cc->freepages)) {
 399                isolate_freepages(cc->zone, cc);
 400
 401                if (list_empty(&cc->freepages))
 402                        return NULL;
 403        }
 404
 405        freepage = list_entry(cc->freepages.next, struct page, lru);
 406        list_del(&freepage->lru);
 407        cc->nr_freepages--;
 408
 409        return freepage;
 410}
 411
 412/*
 413 * We cannot control nr_migratepages and nr_freepages fully when migration is
 414 * running as migrate_pages() has no knowledge of compact_control. When
 415 * migration is complete, we count the number of pages on the lists by hand.
 416 */
 417static void update_nr_listpages(struct compact_control *cc)
 418{
 419        int nr_migratepages = 0;
 420        int nr_freepages = 0;
 421        struct page *page;
 422
 423        list_for_each_entry(page, &cc->migratepages, lru)
 424                nr_migratepages++;
 425        list_for_each_entry(page, &cc->freepages, lru)
 426                nr_freepages++;
 427
 428        cc->nr_migratepages = nr_migratepages;
 429        cc->nr_freepages = nr_freepages;
 430}
 431
 432static int compact_finished(struct zone *zone,
 433                            struct compact_control *cc)
 434{
 435        unsigned int order;
 436        unsigned long watermark;
 437
 438        if (fatal_signal_pending(current))
 439                return COMPACT_PARTIAL;
 440
 441        /* Compaction run completes if the migrate and free scanner meet */
 442        if (cc->free_pfn <= cc->migrate_pfn)
 443                return COMPACT_COMPLETE;
 444
 445        /*
 446         * order == -1 is expected when compacting via
 447         * /proc/sys/vm/compact_memory
 448         */
 449        if (cc->order == -1)
 450                return COMPACT_CONTINUE;
 451
 452        /* Compaction run is not finished if the watermark is not met */
 453        watermark = low_wmark_pages(zone);
 454        watermark += (1 << cc->order);
 455
 456        if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0))
 457                return COMPACT_CONTINUE;
 458
 459        /* Direct compactor: Is a suitable page free? */
 460        for (order = cc->order; order < MAX_ORDER; order++) {
 461                /* Job done if page is free of the right migratetype */
 462                if (!list_empty(&zone->free_area[order].free_list[cc->migratetype]))
 463                        return COMPACT_PARTIAL;
 464
 465                /* Job done if allocation would set block type */
 466                if (order >= pageblock_order && zone->free_area[order].nr_free)
 467                        return COMPACT_PARTIAL;
 468        }
 469
 470        return COMPACT_CONTINUE;
 471}
 472
 473/*
 474 * compaction_suitable: Is this suitable to run compaction on this zone now?
 475 * Returns
 476 *   COMPACT_SKIPPED  - If there are too few free pages for compaction
 477 *   COMPACT_PARTIAL  - If the allocation would succeed without compaction
 478 *   COMPACT_CONTINUE - If compaction should run now
 479 */
 480unsigned long compaction_suitable(struct zone *zone, int order)
 481{
 482        int fragindex;
 483        unsigned long watermark;
 484
 485        /*
 486         * order == -1 is expected when compacting via
 487         * /proc/sys/vm/compact_memory
 488         */
 489        if (order == -1)
 490                return COMPACT_CONTINUE;
 491
 492        /*
 493         * Watermarks for order-0 must be met for compaction. Note the 2UL.
 494         * This is because during migration, copies of pages need to be
 495         * allocated and for a short time, the footprint is higher
 496         */
 497        watermark = low_wmark_pages(zone) + (2UL << order);
 498        if (!zone_watermark_ok(zone, 0, watermark, 0, 0))
 499                return COMPACT_SKIPPED;
 500
 501        /*
 502         * fragmentation index determines if allocation failures are due to
 503         * low memory or external fragmentation
 504         *
 505         * index of -1000 implies allocations might succeed depending on
 506         * watermarks
 507         * index towards 0 implies failure is due to lack of memory
 508         * index towards 1000 implies failure is due to fragmentation
 509         *
 510         * Only compact if a failure would be due to fragmentation.
 511         */
 512        fragindex = fragmentation_index(zone, order);
 513        if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
 514                return COMPACT_SKIPPED;
 515
 516        if (fragindex == -1000 && zone_watermark_ok(zone, order, watermark,
 517            0, 0))
 518                return COMPACT_PARTIAL;
 519
 520        return COMPACT_CONTINUE;
 521}
 522
 523static int compact_zone(struct zone *zone, struct compact_control *cc)
 524{
 525        int ret;
 526
 527        ret = compaction_suitable(zone, cc->order);
 528        switch (ret) {
 529        case COMPACT_PARTIAL:
 530        case COMPACT_SKIPPED:
 531                /* Compaction is likely to fail */
 532                return ret;
 533        case COMPACT_CONTINUE:
 534                /* Fall through to compaction */
 535                ;
 536        }
 537
 538        /* Setup to move all movable pages to the end of the zone */
 539        cc->migrate_pfn = zone->zone_start_pfn;
 540        cc->free_pfn = cc->migrate_pfn + zone->spanned_pages;
 541        cc->free_pfn &= ~(pageblock_nr_pages-1);
 542
 543        migrate_prep_local();
 544
 545        while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) {
 546                unsigned long nr_migrate, nr_remaining;
 547                int err;
 548
 549                switch (isolate_migratepages(zone, cc)) {
 550                case ISOLATE_ABORT:
 551                        ret = COMPACT_PARTIAL;
 552                        goto out;
 553                case ISOLATE_NONE:
 554                        continue;
 555                case ISOLATE_SUCCESS:
 556                        ;
 557                }
 558
 559                nr_migrate = cc->nr_migratepages;
 560                err = migrate_pages(&cc->migratepages, compaction_alloc,
 561                                (unsigned long)cc, false,
 562                                cc->sync);
 563                update_nr_listpages(cc);
 564                nr_remaining = cc->nr_migratepages;
 565
 566                count_vm_event(COMPACTBLOCKS);
 567                count_vm_events(COMPACTPAGES, nr_migrate - nr_remaining);
 568                if (nr_remaining)
 569                        count_vm_events(COMPACTPAGEFAILED, nr_remaining);
 570                trace_mm_compaction_migratepages(nr_migrate - nr_remaining,
 571                                                nr_remaining);
 572
 573                /* Release LRU pages not migrated */
 574                if (err) {
 575                        putback_lru_pages(&cc->migratepages);
 576                        cc->nr_migratepages = 0;
 577                }
 578
 579        }
 580
 581out:
 582        /* Release free pages and check accounting */
 583        cc->nr_freepages -= release_freepages(&cc->freepages);
 584        VM_BUG_ON(cc->nr_freepages != 0);
 585
 586        return ret;
 587}
 588
 589unsigned long compact_zone_order(struct zone *zone,
 590                                 int order, gfp_t gfp_mask,
 591                                 bool sync)
 592{
 593        struct compact_control cc = {
 594                .nr_freepages = 0,
 595                .nr_migratepages = 0,
 596                .order = order,
 597                .migratetype = allocflags_to_migratetype(gfp_mask),
 598                .zone = zone,
 599                .sync = sync,
 600        };
 601        INIT_LIST_HEAD(&cc.freepages);
 602        INIT_LIST_HEAD(&cc.migratepages);
 603
 604        return compact_zone(zone, &cc);
 605}
 606
 607int sysctl_extfrag_threshold = 500;
 608
 609/**
 610 * try_to_compact_pages - Direct compact to satisfy a high-order allocation
 611 * @zonelist: The zonelist used for the current allocation
 612 * @order: The order of the current allocation
 613 * @gfp_mask: The GFP mask of the current allocation
 614 * @nodemask: The allowed nodes to allocate from
 615 * @sync: Whether migration is synchronous or not
 616 *
 617 * This is the main entry point for direct page compaction.
 618 */
 619unsigned long try_to_compact_pages(struct zonelist *zonelist,
 620                        int order, gfp_t gfp_mask, nodemask_t *nodemask,
 621                        bool sync)
 622{
 623        enum zone_type high_zoneidx = gfp_zone(gfp_mask);
 624        int may_enter_fs = gfp_mask & __GFP_FS;
 625        int may_perform_io = gfp_mask & __GFP_IO;
 626        struct zoneref *z;
 627        struct zone *zone;
 628        int rc = COMPACT_SKIPPED;
 629
 630        /*
 631         * Check whether it is worth even starting compaction. The order check is
 632         * made because an assumption is made that the page allocator can satisfy
 633         * the "cheaper" orders without taking special steps
 634         */
 635        if (!order || !may_enter_fs || !may_perform_io)
 636                return rc;
 637
 638        count_vm_event(COMPACTSTALL);
 639
 640        /* Compact each zone in the list */
 641        for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx,
 642                                                                nodemask) {
 643                int status;
 644
 645                status = compact_zone_order(zone, order, gfp_mask, sync);
 646                rc = max(status, rc);
 647
 648                /* If a normal allocation would succeed, stop compacting */
 649                if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0))
 650                        break;
 651        }
 652
 653        return rc;
 654}
 655
 656
 657/* Compact all zones within a node */
 658static int compact_node(int nid)
 659{
 660        int zoneid;
 661        pg_data_t *pgdat;
 662        struct zone *zone;
 663
 664        if (nid < 0 || nid >= nr_node_ids || !node_online(nid))
 665                return -EINVAL;
 666        pgdat = NODE_DATA(nid);
 667
 668        /* Flush pending updates to the LRU lists */
 669        lru_add_drain_all();
 670
 671        for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
 672                struct compact_control cc = {
 673                        .nr_freepages = 0,
 674                        .nr_migratepages = 0,
 675                        .order = -1,
 676                };
 677
 678                zone = &pgdat->node_zones[zoneid];
 679                if (!populated_zone(zone))
 680                        continue;
 681
 682                cc.zone = zone;
 683                INIT_LIST_HEAD(&cc.freepages);
 684                INIT_LIST_HEAD(&cc.migratepages);
 685
 686                compact_zone(zone, &cc);
 687
 688                VM_BUG_ON(!list_empty(&cc.freepages));
 689                VM_BUG_ON(!list_empty(&cc.migratepages));
 690        }
 691
 692        return 0;
 693}
 694
 695/* Compact all nodes in the system */
 696static int compact_nodes(void)
 697{
 698        int nid;
 699
 700        for_each_online_node(nid)
 701                compact_node(nid);
 702
 703        return COMPACT_COMPLETE;
 704}
 705
 706/* The written value is actually unused, all memory is compacted */
 707int sysctl_compact_memory;
 708
 709/* This is the entry point for compacting all nodes via /proc/sys/vm */
 710int sysctl_compaction_handler(struct ctl_table *table, int write,
 711                        void __user *buffer, size_t *length, loff_t *ppos)
 712{
 713        if (write)
 714                return compact_nodes();
 715
 716        return 0;
 717}
 718
 719int sysctl_extfrag_handler(struct ctl_table *table, int write,
 720                        void __user *buffer, size_t *length, loff_t *ppos)
 721{
 722        proc_dointvec_minmax(table, write, buffer, length, ppos);
 723
 724        return 0;
 725}
 726
 727#if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA)
 728ssize_t sysfs_compact_node(struct sys_device *dev,
 729                        struct sysdev_attribute *attr,
 730                        const char *buf, size_t count)
 731{
 732        compact_node(dev->id);
 733
 734        return count;
 735}
 736static SYSDEV_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node);
 737
 738int compaction_register_node(struct node *node)
 739{
 740        return sysdev_create_file(&node->sysdev, &attr_compact);
 741}
 742
 743void compaction_unregister_node(struct node *node)
 744{
 745        return sysdev_remove_file(&node->sysdev, &attr_compact);
 746}
 747#endif /* CONFIG_SYSFS && CONFIG_NUMA */
 748
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