/* * linux/mm/compaction.c * * Memory compaction for the reduction of external fragmentation. Note that * this heavily depends upon page migration to do all the real heavy * lifting * * Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie> */#include <linux/swap.h>#include <linux/migrate.h>#include <linux/compaction.h>#include <linux/mm_inline.h>#include <linux/backing-dev.h>#include <linux/sysctl.h>#include <linux/sysfs.h>#include "internal.h" #define CREATE_TRACE_POINTS#include <trace/events/compaction.h> /* * compact_control is used to track pages being migrated and the free pages * they are being migrated to during memory compaction. The free_pfn starts * at the end of a zone and migrate_pfn begins at the start. Movable pages * are moved to the end of a zone during a compaction run and the run * completes when free_pfn <= migrate_pfn */struct compact_control { struct list_head freepages; /* List of free pages to migrate to */ struct list_head migratepages; /* List of pages being migrated */ unsigned long nr_freepages; /* Number of isolated free pages */ unsigned long nr_migratepages; /* Number of pages to migrate */ unsigned long free_pfn; /* isolate_freepages search base */ unsigned long migrate_pfn; /* isolate_migratepages search base */ bool sync; /* Synchronous migration */ unsigned int order; /* order a direct compactor needs */ int migratetype; /* MOVABLE, RECLAIMABLE etc */ struct zone *zone;}; static unsigned long release_freepages(struct list_head *freelist){ struct page *page, *next; unsigned long count = 0; list_for_each_entry_safe(page, next, freelist, lru) { list_del(&page->lru); __free_page(page); count++; } return count;} /* Isolate free pages onto a private freelist. Must hold zone->lock */static unsigned long isolate_freepages_block(struct zone *zone, unsigned long blockpfn, struct list_head *freelist){ unsigned long zone_end_pfn, end_pfn; int nr_scanned = 0, total_isolated = 0; struct page *cursor; /* Get the last PFN we should scan for free pages at */ zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages; end_pfn = min(blockpfn + pageblock_nr_pages, zone_end_pfn); /* Find the first usable PFN in the block to initialse page cursor */ for (; blockpfn < end_pfn; blockpfn++) { if (pfn_valid_within(blockpfn)) break; } cursor = pfn_to_page(blockpfn); /* Isolate free pages. This assumes the block is valid */ for (; blockpfn < end_pfn; blockpfn++, cursor++) { int isolated, i; struct page *page = cursor; if (!pfn_valid_within(blockpfn)) continue; nr_scanned++; if (!PageBuddy(page)) continue; /* Found a free page, break it into order-0 pages */ isolated = split_free_page(page); total_isolated += isolated; for (i = 0; i < isolated; i++) { list_add(&page->lru, freelist); page++; } /* If a page was split, advance to the end of it */ if (isolated) { blockpfn += isolated - 1; cursor += isolated - 1; } } trace_mm_compaction_isolate_freepages(nr_scanned, total_isolated); return total_isolated;} /* Returns true if the page is within a block suitable for migration to */static bool suitable_migration_target(struct page *page){ int migratetype = get_pageblock_migratetype(page); /* Don't interfere with memory hot-remove or the min_free_kbytes blocks */ if (migratetype == MIGRATE_ISOLATE || migratetype == MIGRATE_RESERVE) return false; /* If the page is a large free page, then allow migration */ if (PageBuddy(page) && page_order(page) >= pageblock_order) return true; /* If the block is MIGRATE_MOVABLE, allow migration */ if (migratetype == MIGRATE_MOVABLE) return true; /* Otherwise skip the block */ return false;} /* * Based on information in the current compact_control, find blocks * suitable for isolating free pages from and then isolate them. */static void isolate_freepages(struct zone *zone, struct compact_control *cc){ struct page *page; unsigned long high_pfn, low_pfn, pfn; unsigned long flags; int nr_freepages = cc->nr_freepages; struct list_head *freelist = &cc->freepages; /* * Initialise the free scanner. The starting point is where we last * scanned from (or the end of the zone if starting). The low point * is the end of the pageblock the migration scanner is using. */ pfn = cc->free_pfn; low_pfn = cc->migrate_pfn + pageblock_nr_pages; /* * Take care that if the migration scanner is at the end of the zone * that the free scanner does not accidentally move to the next zone * in the next isolation cycle. */ high_pfn = min(low_pfn, pfn); /* * Isolate free pages until enough are available to migrate the * pages on cc->migratepages. We stop searching if the migrate * and free page scanners meet or enough free pages are isolated. */ for (; pfn > low_pfn && cc->nr_migratepages > nr_freepages; pfn -= pageblock_nr_pages) { unsigned long isolated; if (!pfn_valid(pfn)) continue; /* * Check for overlapping nodes/zones. It's possible on some * configurations to have a setup like * node0 node1 node0 * i.e. it's possible that all pages within a zones range of * pages do not belong to a single zone. */ page = pfn_to_page(pfn); if (page_zone(page) != zone) continue; /* Check the block is suitable for migration */ if (!suitable_migration_target(page)) continue; /* * Found a block suitable for isolating free pages from. Now * we disabled interrupts, double check things are ok and * isolate the pages. This is to minimise the time IRQs * are disabled */ isolated = 0; spin_lock_irqsave(&zone->lock, flags); if (suitable_migration_target(page)) { isolated = isolate_freepages_block(zone, pfn, freelist); nr_freepages += isolated; } spin_unlock_irqrestore(&zone->lock, flags); /* * Record the highest PFN we isolated pages from. When next * looking for free pages, the search will restart here as * page migration may have returned some pages to the allocator */ if (isolated) high_pfn = max(high_pfn, pfn); } /* split_free_page does not map the pages */ list_for_each_entry(page, freelist, lru) { arch_alloc_page(page, 0); kernel_map_pages(page, 1, 1); } cc->free_pfn = high_pfn; cc->nr_freepages = nr_freepages;} /* Update the number of anon and file isolated pages in the zone */static void acct_isolated(struct zone *zone, struct compact_control *cc){ struct page *page; unsigned int count[2] = { 0, }; list_for_each_entry(page, &cc->migratepages, lru) count[!!page_is_file_cache(page)]++; __mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]); __mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]);} /* Similar to reclaim, but different enough that they don't share logic */static bool too_many_isolated(struct zone *zone){ unsigned long active, inactive, isolated; inactive = zone_page_state(zone, NR_INACTIVE_FILE) + zone_page_state(zone, NR_INACTIVE_ANON); active = zone_page_state(zone, NR_ACTIVE_FILE) + zone_page_state(zone, NR_ACTIVE_ANON); isolated = zone_page_state(zone, NR_ISOLATED_FILE) + zone_page_state(zone, NR_ISOLATED_ANON); return isolated > (inactive + active) / 2;} /* possible outcome of isolate_migratepages */typedef enum { ISOLATE_ABORT, /* Abort compaction now */ ISOLATE_NONE, /* No pages isolated, continue scanning */ ISOLATE_SUCCESS, /* Pages isolated, migrate */} isolate_migrate_t; /* * Isolate all pages that can be migrated from the block pointed to by * the migrate scanner within compact_control. */static isolate_migrate_t isolate_migratepages(struct zone *zone, struct compact_control *cc){ unsigned long low_pfn, end_pfn; unsigned long last_pageblock_nr = 0, pageblock_nr; unsigned long nr_scanned = 0, nr_isolated = 0; struct list_head *migratelist = &cc->migratepages; isolate_mode_t mode = ISOLATE_ACTIVE|ISOLATE_INACTIVE; /* Do not scan outside zone boundaries */ low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn); /* Only scan within a pageblock boundary */ end_pfn = ALIGN(low_pfn + pageblock_nr_pages, pageblock_nr_pages); /* Do not cross the free scanner or scan within a memory hole */ if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) { cc->migrate_pfn = end_pfn; return ISOLATE_NONE; } /* * Ensure that there are not too many pages isolated from the LRU * list by either parallel reclaimers or compaction. If there are, * delay for some time until fewer pages are isolated */ while (unlikely(too_many_isolated(zone))) { /* async migration should just abort */ if (!cc->sync) return ISOLATE_ABORT; congestion_wait(BLK_RW_ASYNC, HZ/10); if (fatal_signal_pending(current)) return ISOLATE_ABORT; } /* Time to isolate some pages for migration */ cond_resched(); spin_lock_irq(&zone->lru_lock); for (; low_pfn < end_pfn; low_pfn++) { struct page *page; bool locked = true; /* give a chance to irqs before checking need_resched() */ if (!((low_pfn+1) % SWAP_CLUSTER_MAX)) { spin_unlock_irq(&zone->lru_lock); locked = false; } if (need_resched() || spin_is_contended(&zone->lru_lock)) { if (locked) spin_unlock_irq(&zone->lru_lock); cond_resched(); spin_lock_irq(&zone->lru_lock); if (fatal_signal_pending(current)) break; } else if (!locked) spin_lock_irq(&zone->lru_lock); if (!pfn_valid_within(low_pfn)) continue; nr_scanned++; /* Get the page and skip if free */ page = pfn_to_page(low_pfn); if (PageBuddy(page)) continue; /* * For async migration, also only scan in MOVABLE blocks. Async * migration is optimistic to see if the minimum amount of work * satisfies the allocation */ pageblock_nr = low_pfn >> pageblock_order; if (!cc->sync && last_pageblock_nr != pageblock_nr && get_pageblock_migratetype(page) != MIGRATE_MOVABLE) { low_pfn += pageblock_nr_pages; low_pfn = ALIGN(low_pfn, pageblock_nr_pages) - 1; last_pageblock_nr = pageblock_nr; continue; } if (!PageLRU(page)) continue; /* * PageLRU is set, and lru_lock excludes isolation, * splitting and collapsing (collapsing has already * happened if PageLRU is set). */ if (PageTransHuge(page)) { low_pfn += (1 << compound_order(page)) - 1; continue; } if (!cc->sync) mode |= ISOLATE_CLEAN; /* Try isolate the page */ if (__isolate_lru_page(page, mode, 0) != 0) continue; VM_BUG_ON(PageTransCompound(page)); /* Successfully isolated */ del_page_from_lru_list(zone, page, page_lru(page)); list_add(&page->lru, migratelist); cc->nr_migratepages++; nr_isolated++; /* Avoid isolating too much */ if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) break; } acct_isolated(zone, cc); spin_unlock_irq(&zone->lru_lock); cc->migrate_pfn = low_pfn; trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated); return ISOLATE_SUCCESS;} /* * This is a migrate-callback that "allocates" freepages by taking pages * from the isolated freelists in the block we are migrating to. */static struct page *compaction_alloc(struct page *migratepage, unsigned long data, int **result){ struct compact_control *cc = (struct compact_control *)data; struct page *freepage; /* Isolate free pages if necessary */ if (list_empty(&cc->freepages)) { isolate_freepages(cc->zone, cc); if (list_empty(&cc->freepages)) return NULL; } freepage = list_entry(cc->freepages.next, struct page, lru); list_del(&freepage->lru); cc->nr_freepages--; return freepage;} /* * We cannot control nr_migratepages and nr_freepages fully when migration is * running as migrate_pages() has no knowledge of compact_control. When * migration is complete, we count the number of pages on the lists by hand. */static void update_nr_listpages(struct compact_control *cc){ int nr_migratepages = 0; int nr_freepages = 0; struct page *page; list_for_each_entry(page, &cc->migratepages, lru) nr_migratepages++; list_for_each_entry(page, &cc->freepages, lru) nr_freepages++; cc->nr_migratepages = nr_migratepages; cc->nr_freepages = nr_freepages;} static int compact_finished(struct zone *zone, struct compact_control *cc){ unsigned int order; unsigned long watermark; if (fatal_signal_pending(current)) return COMPACT_PARTIAL; /* Compaction run completes if the migrate and free scanner meet */ if (cc->free_pfn <= cc->migrate_pfn) return COMPACT_COMPLETE; /* * order == -1 is expected when compacting via * /proc/sys/vm/compact_memory */ if (cc->order == -1) return COMPACT_CONTINUE; /* Compaction run is not finished if the watermark is not met */ watermark = low_wmark_pages(zone); watermark += (1 << cc->order); if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0)) return COMPACT_CONTINUE; /* Direct compactor: Is a suitable page free? */ for (order = cc->order; order < MAX_ORDER; order++) { /* Job done if page is free of the right migratetype */ if (!list_empty(&zone->free_area[order].free_list[cc->migratetype])) return COMPACT_PARTIAL; /* Job done if allocation would set block type */ if (order >= pageblock_order && zone->free_area[order].nr_free) return COMPACT_PARTIAL; } return COMPACT_CONTINUE;} /* * compaction_suitable: Is this suitable to run compaction on this zone now? * Returns * COMPACT_SKIPPED - If there are too few free pages for compaction * COMPACT_PARTIAL - If the allocation would succeed without compaction * COMPACT_CONTINUE - If compaction should run now */unsigned long compaction_suitable(struct zone *zone, int order){ int fragindex; unsigned long watermark; /* * order == -1 is expected when compacting via * /proc/sys/vm/compact_memory */ if (order == -1) return COMPACT_CONTINUE; /* * Watermarks for order-0 must be met for compaction. Note the 2UL. * This is because during migration, copies of pages need to be * allocated and for a short time, the footprint is higher */ watermark = low_wmark_pages(zone) + (2UL << order); if (!zone_watermark_ok(zone, 0, watermark, 0, 0)) return COMPACT_SKIPPED; /* * fragmentation index determines if allocation failures are due to * low memory or external fragmentation *Lines 1–500 of 743. Load more
/* * linux/mm/compaction.c * * Memory compaction for the reduction of external fragmentation. Note that * this heavily depends upon page migration to do all the real heavy * lifting * * Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie> */ #include <linux/swap.h> #include <linux/migrate.h> #include <linux/compaction.h> #include <linux/mm_inline.h> #include <linux/backing-dev.h> #include <linux/sysctl.h> #include <linux/sysfs.h> #include "internal.h" #define CREATE_TRACE_POINTS #include <trace/events/compaction.h> /* * compact_control is used to track pages being migrated and the free pages * they are being migrated to during memory compaction. The free_pfn starts * at the end of a zone and migrate_pfn begins at the start. Movable pages * are moved to the end of a zone during a compaction run and the run * completes when free_pfn <= migrate_pfn */ struct compact_control { struct list_head freepages; /* List of free pages to migrate to */ struct list_head migratepages; /* List of pages being migrated */ unsigned long nr_freepages; /* Number of isolated free pages */ unsigned long nr_migratepages; /* Number of pages to migrate */ unsigned long free_pfn; /* isolate_freepages search base */ unsigned long migrate_pfn; /* isolate_migratepages search base */ bool sync; /* Synchronous migration */ unsigned int order; /* order a direct compactor needs */ int migratetype; /* MOVABLE, RECLAIMABLE etc */ struct zone *zone; }; static unsigned long release_freepages(struct list_head *freelist) { struct page *page, *next; unsigned long count = 0; list_for_each_entry_safe(page, next, freelist, lru) { list_del(&page->lru); __free_page(page); count++; } return count; } /* Isolate free pages onto a private freelist. Must hold zone->lock */ static unsigned long isolate_freepages_block(struct zone *zone, unsigned long blockpfn, struct list_head *freelist) { unsigned long zone_end_pfn, end_pfn; int nr_scanned = 0, total_isolated = 0; struct page *cursor; /* Get the last PFN we should scan for free pages at */ zone_end_pfn = zone->zone_start_pfn + zone->spanned_pages; end_pfn = min(blockpfn + pageblock_nr_pages, zone_end_pfn); /* Find the first usable PFN in the block to initialse page cursor */ for (; blockpfn < end_pfn; blockpfn++) { if (pfn_valid_within(blockpfn)) break; } cursor = pfn_to_page(blockpfn); /* Isolate free pages. This assumes the block is valid */ for (; blockpfn < end_pfn; blockpfn++, cursor++) { int isolated, i; struct page *page = cursor; if (!pfn_valid_within(blockpfn)) continue; nr_scanned++; if (!PageBuddy(page)) continue; /* Found a free page, break it into order-0 pages */ isolated = split_free_page(page); total_isolated += isolated; for (i = 0; i < isolated; i++) { list_add(&page->lru, freelist); page++; } /* If a page was split, advance to the end of it */ if (isolated) { blockpfn += isolated - 1; cursor += isolated - 1; } } trace_mm_compaction_isolate_freepages(nr_scanned, total_isolated); return total_isolated; } /* Returns true if the page is within a block suitable for migration to */ static bool suitable_migration_target(struct page *page) { int migratetype = get_pageblock_migratetype(page); /* Don't interfere with memory hot-remove or the min_free_kbytes blocks */ if (migratetype == MIGRATE_ISOLATE || migratetype == MIGRATE_RESERVE) return false; /* If the page is a large free page, then allow migration */ if (PageBuddy(page) && page_order(page) >= pageblock_order) return true; /* If the block is MIGRATE_MOVABLE, allow migration */ if (migratetype == MIGRATE_MOVABLE) return true; /* Otherwise skip the block */ return false; } /* * Based on information in the current compact_control, find blocks * suitable for isolating free pages from and then isolate them. */ static void isolate_freepages(struct zone *zone, struct compact_control *cc) { struct page *page; unsigned long high_pfn, low_pfn, pfn; unsigned long flags; int nr_freepages = cc->nr_freepages; struct list_head *freelist = &cc->freepages; /* * Initialise the free scanner. The starting point is where we last * scanned from (or the end of the zone if starting). The low point * is the end of the pageblock the migration scanner is using. */ pfn = cc->free_pfn; low_pfn = cc->migrate_pfn + pageblock_nr_pages; /* * Take care that if the migration scanner is at the end of the zone * that the free scanner does not accidentally move to the next zone * in the next isolation cycle. */ high_pfn = min(low_pfn, pfn); /* * Isolate free pages until enough are available to migrate the * pages on cc->migratepages. We stop searching if the migrate * and free page scanners meet or enough free pages are isolated. */ for (; pfn > low_pfn && cc->nr_migratepages > nr_freepages; pfn -= pageblock_nr_pages) { unsigned long isolated; if (!pfn_valid(pfn)) continue; /* * Check for overlapping nodes/zones. It's possible on some * configurations to have a setup like * node0 node1 node0 * i.e. it's possible that all pages within a zones range of * pages do not belong to a single zone. */ page = pfn_to_page(pfn); if (page_zone(page) != zone) continue; /* Check the block is suitable for migration */ if (!suitable_migration_target(page)) continue; /* * Found a block suitable for isolating free pages from. Now * we disabled interrupts, double check things are ok and * isolate the pages. This is to minimise the time IRQs * are disabled */ isolated = 0; spin_lock_irqsave(&zone->lock, flags); if (suitable_migration_target(page)) { isolated = isolate_freepages_block(zone, pfn, freelist); nr_freepages += isolated; } spin_unlock_irqrestore(&zone->lock, flags); /* * Record the highest PFN we isolated pages from. When next * looking for free pages, the search will restart here as * page migration may have returned some pages to the allocator */ if (isolated) high_pfn = max(high_pfn, pfn); } /* split_free_page does not map the pages */ list_for_each_entry(page, freelist, lru) { arch_alloc_page(page, 0); kernel_map_pages(page, 1, 1); } cc->free_pfn = high_pfn; cc->nr_freepages = nr_freepages; } /* Update the number of anon and file isolated pages in the zone */ static void acct_isolated(struct zone *zone, struct compact_control *cc) { struct page *page; unsigned int count[2] = { 0, }; list_for_each_entry(page, &cc->migratepages, lru) count[!!page_is_file_cache(page)]++; __mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]); __mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]); } /* Similar to reclaim, but different enough that they don't share logic */ static bool too_many_isolated(struct zone *zone) { unsigned long active, inactive, isolated; inactive = zone_page_state(zone, NR_INACTIVE_FILE) + zone_page_state(zone, NR_INACTIVE_ANON); active = zone_page_state(zone, NR_ACTIVE_FILE) + zone_page_state(zone, NR_ACTIVE_ANON); isolated = zone_page_state(zone, NR_ISOLATED_FILE) + zone_page_state(zone, NR_ISOLATED_ANON); return isolated > (inactive + active) / 2; } /* possible outcome of isolate_migratepages */ typedef enum { ISOLATE_ABORT, /* Abort compaction now */ ISOLATE_NONE, /* No pages isolated, continue scanning */ ISOLATE_SUCCESS, /* Pages isolated, migrate */ } isolate_migrate_t; /* * Isolate all pages that can be migrated from the block pointed to by * the migrate scanner within compact_control. */ static isolate_migrate_t isolate_migratepages(struct zone *zone, struct compact_control *cc) { unsigned long low_pfn, end_pfn; unsigned long last_pageblock_nr = 0, pageblock_nr; unsigned long nr_scanned = 0, nr_isolated = 0; struct list_head *migratelist = &cc->migratepages; isolate_mode_t mode = ISOLATE_ACTIVE|ISOLATE_INACTIVE; /* Do not scan outside zone boundaries */ low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn); /* Only scan within a pageblock boundary */ end_pfn = ALIGN(low_pfn + pageblock_nr_pages, pageblock_nr_pages); /* Do not cross the free scanner or scan within a memory hole */ if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) { cc->migrate_pfn = end_pfn; return ISOLATE_NONE; } /* * Ensure that there are not too many pages isolated from the LRU * list by either parallel reclaimers or compaction. If there are, * delay for some time until fewer pages are isolated */ while (unlikely(too_many_isolated(zone))) { /* async migration should just abort */ if (!cc->sync) return ISOLATE_ABORT; congestion_wait(BLK_RW_ASYNC, HZ/10); if (fatal_signal_pending(current)) return ISOLATE_ABORT; } /* Time to isolate some pages for migration */ cond_resched(); spin_lock_irq(&zone->lru_lock); for (; low_pfn < end_pfn; low_pfn++) { struct page *page; bool locked = true; /* give a chance to irqs before checking need_resched() */ if (!((low_pfn+1) % SWAP_CLUSTER_MAX)) { spin_unlock_irq(&zone->lru_lock); locked = false; } if (need_resched() || spin_is_contended(&zone->lru_lock)) { if (locked) spin_unlock_irq(&zone->lru_lock); cond_resched(); spin_lock_irq(&zone->lru_lock); if (fatal_signal_pending(current)) break; } else if (!locked) spin_lock_irq(&zone->lru_lock); if (!pfn_valid_within(low_pfn)) continue; nr_scanned++; /* Get the page and skip if free */ page = pfn_to_page(low_pfn); if (PageBuddy(page)) continue; /* * For async migration, also only scan in MOVABLE blocks. Async * migration is optimistic to see if the minimum amount of work * satisfies the allocation */ pageblock_nr = low_pfn >> pageblock_order; if (!cc->sync && last_pageblock_nr != pageblock_nr && get_pageblock_migratetype(page) != MIGRATE_MOVABLE) { low_pfn += pageblock_nr_pages; low_pfn = ALIGN(low_pfn, pageblock_nr_pages) - 1; last_pageblock_nr = pageblock_nr; continue; } if (!PageLRU(page)) continue; /* * PageLRU is set, and lru_lock excludes isolation, * splitting and collapsing (collapsing has already * happened if PageLRU is set). */ if (PageTransHuge(page)) { low_pfn += (1 << compound_order(page)) - 1; continue; } if (!cc->sync) mode |= ISOLATE_CLEAN; /* Try isolate the page */ if (__isolate_lru_page(page, mode, 0) != 0) continue; VM_BUG_ON(PageTransCompound(page)); /* Successfully isolated */ del_page_from_lru_list(zone, page, page_lru(page)); list_add(&page->lru, migratelist); cc->nr_migratepages++; nr_isolated++; /* Avoid isolating too much */ if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) break; } acct_isolated(zone, cc); spin_unlock_irq(&zone->lru_lock); cc->migrate_pfn = low_pfn; trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated); return ISOLATE_SUCCESS; } /* * This is a migrate-callback that "allocates" freepages by taking pages * from the isolated freelists in the block we are migrating to. */ static struct page *compaction_alloc(struct page *migratepage, unsigned long data, int **result) { struct compact_control *cc = (struct compact_control *)data; struct page *freepage; /* Isolate free pages if necessary */ if (list_empty(&cc->freepages)) { isolate_freepages(cc->zone, cc); if (list_empty(&cc->freepages)) return NULL; } freepage = list_entry(cc->freepages.next, struct page, lru); list_del(&freepage->lru); cc->nr_freepages--; return freepage; } /* * We cannot control nr_migratepages and nr_freepages fully when migration is * running as migrate_pages() has no knowledge of compact_control. When * migration is complete, we count the number of pages on the lists by hand. */ static void update_nr_listpages(struct compact_control *cc) { int nr_migratepages = 0; int nr_freepages = 0; struct page *page; list_for_each_entry(page, &cc->migratepages, lru) nr_migratepages++; list_for_each_entry(page, &cc->freepages, lru) nr_freepages++; cc->nr_migratepages = nr_migratepages; cc->nr_freepages = nr_freepages; } static int compact_finished(struct zone *zone, struct compact_control *cc) { unsigned int order; unsigned long watermark; if (fatal_signal_pending(current)) return COMPACT_PARTIAL; /* Compaction run completes if the migrate and free scanner meet */ if (cc->free_pfn <= cc->migrate_pfn) return COMPACT_COMPLETE; /* * order == -1 is expected when compacting via * /proc/sys/vm/compact_memory */ if (cc->order == -1) return COMPACT_CONTINUE; /* Compaction run is not finished if the watermark is not met */ watermark = low_wmark_pages(zone); watermark += (1 << cc->order); if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0)) return COMPACT_CONTINUE; /* Direct compactor: Is a suitable page free? */ for (order = cc->order; order < MAX_ORDER; order++) { /* Job done if page is free of the right migratetype */ if (!list_empty(&zone->free_area[order].free_list[cc->migratetype])) return COMPACT_PARTIAL; /* Job done if allocation would set block type */ if (order >= pageblock_order && zone->free_area[order].nr_free) return COMPACT_PARTIAL; } return COMPACT_CONTINUE; } /* * compaction_suitable: Is this suitable to run compaction on this zone now? * Returns * COMPACT_SKIPPED - If there are too few free pages for compaction * COMPACT_PARTIAL - If the allocation would succeed without compaction * COMPACT_CONTINUE - If compaction should run now */ unsigned long compaction_suitable(struct zone *zone, int order) { int fragindex; unsigned long watermark; /* * order == -1 is expected when compacting via * /proc/sys/vm/compact_memory */ if (order == -1) return COMPACT_CONTINUE; /* * Watermarks for order-0 must be met for compaction. Note the 2UL. * This is because during migration, copies of pages need to be * allocated and for a short time, the footprint is higher */ watermark = low_wmark_pages(zone) + (2UL << order); if (!zone_watermark_ok(zone, 0, watermark, 0, 0)) return COMPACT_SKIPPED; /* * fragmentation index determines if allocation failures are due to * low memory or external fragmentation *