/* * 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/cpu.h> #include <linux/swap.h> #include <linux/migrate.h> #include <linux/compaction.h> #include <linux/mm_inline.h> #include <linux/sched/signal.h> #include <linux/backing-dev.h> #include <linux/sysctl.h> #include <linux/sysfs.h> #include <linux/page-isolation.h> #include <linux/kasan.h> #include <linux/kthread.h> #include <linux/freezer.h> #include <linux/page_owner.h> #include "internal.h" #ifdef CONFIG_COMPACTION static inline void count_compact_event(enum vm_event_item item) { count_vm_event(item); } static inline void count_compact_events(enum vm_event_item item, long delta) { count_vm_events(item, delta); } #else #define count_compact_event(item) do { } while (0) #define count_compact_events(item, delta) do { } while (0) #endif #if defined CONFIG_COMPACTION || defined CONFIG_CMA #define CREATE_TRACE_POINTS #include <trace/events/compaction.h> #define block_start_pfn(pfn, order) round_down(pfn, 1UL << (order)) #define block_end_pfn(pfn, order) ALIGN((pfn) + 1, 1UL << (order)) #define pageblock_start_pfn(pfn) block_start_pfn(pfn, pageblock_order) #define pageblock_end_pfn(pfn) block_end_pfn(pfn, pageblock_order) static unsigned long release_freepages(struct list_head *freelist) { struct page *page, *next; unsigned long high_pfn = 0; list_for_each_entry_safe(page, next, freelist, lru) { unsigned long pfn = page_to_pfn(page); list_del(&page->lru); __free_page(page); if (pfn > high_pfn) high_pfn = pfn; } return high_pfn; } static void map_pages(struct list_head *list) { unsigned int i, order, nr_pages; struct page *page, *next; LIST_HEAD(tmp_list); list_for_each_entry_safe(page, next, list, lru) { list_del(&page->lru); order = page_private(page); nr_pages = 1 << order; post_alloc_hook(page, order, __GFP_MOVABLE); if (order) split_page(page, order); for (i = 0; i < nr_pages; i++) { list_add(&page->lru, &tmp_list); page++; } } list_splice(&tmp_list, list); } static inline bool migrate_async_suitable(int migratetype) { return is_migrate_cma(migratetype) || migratetype == MIGRATE_MOVABLE; } #ifdef CONFIG_COMPACTION int PageMovable(struct page *page) { struct address_space *mapping; VM_BUG_ON_PAGE(!PageLocked(page), page); if (!__PageMovable(page)) return 0; mapping = page_mapping(page); if (mapping && mapping->a_ops && mapping->a_ops->isolate_page) return 1; return 0; } EXPORT_SYMBOL(PageMovable); void __SetPageMovable(struct page *page, struct address_space *mapping) { VM_BUG_ON_PAGE(!PageLocked(page), page); VM_BUG_ON_PAGE((unsigned long)mapping & PAGE_MAPPING_MOVABLE, page); page->mapping = (void *)((unsigned long)mapping | PAGE_MAPPING_MOVABLE); } EXPORT_SYMBOL(__SetPageMovable); void __ClearPageMovable(struct page *page) { VM_BUG_ON_PAGE(!PageLocked(page), page); VM_BUG_ON_PAGE(!PageMovable(page), page); /* * Clear registered address_space val with keeping PAGE_MAPPING_MOVABLE * flag so that VM can catch up released page by driver after isolation. * With it, VM migration doesn't try to put it back. */ page->mapping = (void *)((unsigned long)page->mapping & PAGE_MAPPING_MOVABLE); } EXPORT_SYMBOL(__ClearPageMovable); /* Do not skip compaction more than 64 times */ #define COMPACT_MAX_DEFER_SHIFT 6 /* * Compaction is deferred when compaction fails to result in a page * allocation success. 1 << compact_defer_limit compactions are skipped up * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT */ void defer_compaction(struct zone *zone, int order) { zone->compact_considered = 0; zone->compact_defer_shift++; if (order < zone->compact_order_failed) zone->compact_order_failed = order; if (zone->compact_defer_shift > COMPACT_MAX_DEFER_SHIFT) zone->compact_defer_shift = COMPACT_MAX_DEFER_SHIFT; trace_mm_compaction_defer_compaction(zone, order); } /* Returns true if compaction should be skipped this time */ bool compaction_deferred(struct zone *zone, int order) { unsigned long defer_limit = 1UL << zone->compact_defer_shift; if (order < zone->compact_order_failed) return false; /* Avoid possible overflow */ if (++zone->compact_considered > defer_limit) zone->compact_considered = defer_limit; if (zone->compact_considered >= defer_limit) return false; trace_mm_compaction_deferred(zone, order); return true; } /* * Update defer tracking counters after successful compaction of given order, * which means an allocation either succeeded (alloc_success == true) or is * expected to succeed. */ void compaction_defer_reset(struct zone *zone, int order, bool alloc_success) { if (alloc_success) { zone->compact_considered = 0; zone->compact_defer_shift = 0; } if (order >= zone->compact_order_failed) zone->compact_order_failed = order + 1; trace_mm_compaction_defer_reset(zone, order); } /* Returns true if restarting compaction after many failures */ bool compaction_restarting(struct zone *zone, int order) { if (order < zone->compact_order_failed) return false; return zone->compact_defer_shift == COMPACT_MAX_DEFER_SHIFT && zone->compact_considered >= 1UL << zone->compact_defer_shift; } /* Returns true if the pageblock should be scanned for pages to isolate. */ static inline bool isolation_suitable(struct compact_control *cc, struct page *page) { if (cc->ignore_skip_hint) return true; return !get_pageblock_skip(page); } static void reset_cached_positions(struct zone *zone) { zone->compact_cached_migrate_pfn[0] = zone->zone_start_pfn; zone->compact_cached_migrate_pfn[1] = zone->zone_start_pfn; zone->compact_cached_free_pfn = pageblock_start_pfn(zone_end_pfn(zone) - 1); } /* * This function is called to clear all cached information on pageblocks that * should be skipped for page isolation when the migrate and free page scanner * meet. */ static void __reset_isolation_suitable(struct zone *zone) { unsigned long start_pfn = zone->zone_start_pfn; unsigned long end_pfn = zone_end_pfn(zone); unsigned long pfn; zone->compact_blockskip_flush = false; /* Walk the zone and mark every pageblock as suitable for isolation */ for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) { struct page *page; cond_resched(); if (!pfn_valid(pfn)) continue; page = pfn_to_page(pfn); if (zone != page_zone(page)) continue; clear_pageblock_skip(page); } reset_cached_positions(zone); } void reset_isolation_suitable(pg_data_t *pgdat) { int zoneid; for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { struct zone *zone = &pgdat->node_zones[zoneid]; if (!populated_zone(zone)) continue; /* Only flush if a full compaction finished recently */ if (zone->compact_blockskip_flush) __reset_isolation_suitable(zone); } } /* * If no pages were isolated then mark this pageblock to be skipped in the * future. The information is later cleared by __reset_isolation_suitable(). */ static void update_pageblock_skip(struct compact_control *cc, struct page *page, unsigned long nr_isolated, bool migrate_scanner) { struct zone *zone = cc->zone; unsigned long pfn; if (cc->ignore_skip_hint) return; if (!page) return; if (nr_isolated) return; set_pageblock_skip(page); pfn = page_to_pfn(page); /* Update where async and sync compaction should restart */ if (migrate_scanner) { if (pfn > zone->compact_cached_migrate_pfn[0]) zone->compact_cached_migrate_pfn[0] = pfn; if (cc->mode != MIGRATE_ASYNC && pfn > zone->compact_cached_migrate_pfn[1]) zone->compact_cached_migrate_pfn[1] = pfn; } else { if (pfn < zone->compact_cached_free_pfn) zone->compact_cached_free_pfn = pfn; } } #else static inline bool isolation_suitable(struct compact_control *cc, struct page *page) { return true; } static void update_pageblock_skip(struct compact_control *cc, struct page *page, unsigned long nr_isolated, bool migrate_scanner) { } #endif /* CONFIG_COMPACTION */ /* * Compaction requires the taking of some coarse locks that are potentially * very heavily contended. For async compaction, back out if the lock cannot * be taken immediately. For sync compaction, spin on the lock if needed. * * Returns true if the lock is held * Returns false if the lock is not held and compaction should abort */ static bool compact_trylock_irqsave(spinlock_t *lock, unsigned long *flags, struct compact_control *cc) { if (cc->mode == MIGRATE_ASYNC) { if (!spin_trylock_irqsave(lock, *flags)) { cc->contended = true; return false; } } else { spin_lock_irqsave(lock, *flags); } return true; } /* * Compaction requires the taking of some coarse locks that are potentially * very heavily contended. The lock should be periodically unlocked to avoid * having disabled IRQs for a long time, even when there is nobody waiting on * the lock. It might also be that allowing the IRQs will result in * need_resched() becoming true. If scheduling is needed, async compaction * aborts. Sync compaction schedules. * Either compaction type will also abort if a fatal signal is pending. * In either case if the lock was locked, it is dropped and not regained. * * Returns true if compaction should abort due to fatal signal pending, or * async compaction due to need_resched() * Returns false when compaction can continue (sync compaction might have * scheduled) */ static bool compact_unlock_should_abort(spinlock_t *lock, unsigned long flags, bool *locked, struct compact_control *cc) { if (*locked) { spin_unlock_irqrestore(lock, flags); *locked = false; } if (fatal_signal_pending(current)) { cc->contended = true; return true; } if (need_resched()) { if (cc->mode == MIGRATE_ASYNC) { cc->contended = true; return true; } cond_resched(); } return false; } /* * Aside from avoiding lock contention, compaction also periodically checks * need_resched() and either schedules in sync compaction or aborts async * compaction. This is similar to what compact_unlock_should_abort() does, but * is used where no lock is concerned. * * Returns false when no scheduling was needed, or sync compaction scheduled. * Returns true when async compaction should abort. */ static inline bool compact_should_abort(struct compact_control *cc) { /* async compaction aborts if contended */ if (need_resched()) { if (cc->mode == MIGRATE_ASYNC) { cc->contended = true; return true; } cond_resched(); } return false; } /* * Isolate free pages onto a private freelist. If @strict is true, will abort * returning 0 on any invalid PFNs or non-free pages inside of the pageblock * (even though it may still end up isolating some pages). */ static unsigned long isolate_freepages_block(struct compact_control *cc, unsigned long *start_pfn, unsigned long end_pfn, struct list_head *freelist, bool strict) { int nr_scanned = 0, total_isolated = 0; struct page *cursor, *valid_page = NULL; unsigned long flags = 0; bool locked = false; unsigned long blockpfn = *start_pfn; unsigned int order; cursor = pfn_to_page(blockpfn); /* Isolate free pages. */ for (; blockpfn < end_pfn; blockpfn++, cursor++) { int isolated; struct page *page = cursor; /* * Periodically drop the lock (if held) regardless of its * contention, to give chance to IRQs. Abort if fatal signal * pending or async compaction detects need_resched() */ if (!(blockpfn % SWAP_CLUSTER_MAX) && compact_unlock_should_abort(&cc->zone->lock, flags, &locked, cc)) break; nr_scanned++; if (!pfn_valid_within(blockpfn)) goto isolate_fail; if (!valid_page) valid_page = page; /* * For compound pages such as THP and hugetlbfs, we can save * potentially a lot of iterations if we skip them at once. * The check is racy, but we can consider only valid values * and the only danger is skipping too much. */ if (PageCompound(page)) { unsigned int comp_order = compound_order(page); if (likely(comp_order < MAX_ORDER)) { blockpfn += (1UL << comp_order) - 1; cursor += (1UL << comp_order) - 1; } goto isolate_fail; } if (!PageBuddy(page)) goto isolate_fail; /* * If we already hold the lock, we can skip some rechecking. * Note that if we hold the lock now, checked_pageblock was * already set in some previous iteration (or strict is true), * so it is correct to skip the suitable migration target * recheck as well. */ if (!locked) { /* * The zone lock must be held to isolate freepages. * Unfortunately this is a very coarse lock and can be * heavily contended if there are parallel allocations * or parallel compactions. For async compaction do not * spin on the lock and we acquire the lock as late as * possible. */ locked = compact_trylock_irqsave(&cc->zone->lock, &flags, cc); if (!locked) break; /* Recheck this is a buddy page under lock */ if (!PageBuddy(page)) goto isolate_fail; } /* Found a free page, will break it into order-0 pages */ order = page_order(page); isolated = __isolate_free_page(page, order); if (!isolated) break; set_page_private(page, order); total_isolated += isolated; cc->nr_freepages += isolated; list_add_tail(&page->lru, freelist); if (!strict && cc->nr_migratepages <= cc->nr_freepages) { blockpfn += isolated; break; } /* Advance to the end of split page */ blockpfn += isolated - 1; cursor += isolated - 1; continue; isolate_fail: if (strict) break; else continue; } if (locked) spin_unlock_irqrestore(&cc->zone->lock, flags); /* * There is a tiny chance that we have read bogus compound_order(), * so be careful to not go outside of the pageblock. */ if (unlikely(blockpfn > end_pfn)) blockpfn = end_pfn; trace_mm_compaction_isolate_freepages(*start_pfn, blockpfn, nr_scanned, total_isolated); /* Record how far we have got within the block */ *start_pfn = blockpfn; /* * If strict isolation is requested by CMA then check that all the * pages requested were isolated. If there were any failures, 0 is * returned and CMA will fail. */ if (strict && blockpfn < end_pfn) total_isolated = 0; /* Update the pageblock-skip if the whole pageblock was scanned */ if (blockpfn == end_pfn) update_pageblock_skip(cc, valid_page, total_isolated, false); cc->total_free_scanned += nr_scanned; if (total_isolated) count_compact_events(COMPACTISOLATED, total_isolated); return total_isolated; } /** * isolate_freepages_range() - isolate free pages. * @start_pfn: The first PFN to start isolating. * @end_pfn: The one-past-last PFN. * * Non-free pages, invalid PFNs, or zone boundaries within the * [start_pfn, end_pfn) range are considered errors, cause function to * undo its actions and return zero. * * Otherwise, function returns one-past-the-last PFN of isolated page * (which may be greater then end_pfn if end fell in a middle of * a free page). */ unsigned long isolate_freepages_range(struct compact_control *cc, unsigned long start_pfn, unsigned long end_pfn) { unsigned long isolated, pfn, block_start_pfn, block_end_pfn; LIST_HEAD(freelist); pfn = start_pfn; block_start_pfn = pageblock_start_pfn(pfn); if (block_start_pfn < cc->zone->zone_start_pfn) block_start_pfn = cc->zone->zone_start_pfn; block_end_pfn = pageblock_end_pfn(pfn); for (; pfn < end_pfn; pfn += isolated, block_start_pfn = block_end_pfn, block_end_pfn += pageblock_nr_pages) { /* Protect pfn from changing by isolate_freepages_block */ unsigned long isolate_start_pfn = pfn; block_end_pfn = min(block_end_pfn, end_pfn); /* * pfn could pass the block_end_pfn if isolated freepage * is more than pageblock order. In this case, we adjust * scanning range to right one. */ if (pfn >= block_end_pfn) { block_start_pfn = pageblock_start_pfn(pfn); block_end_pfn = pageblock_end_pfn(pfn); block_end_pfn = min(block_end_pfn, end_pfn); } if (!pageblock_pfn_to_page(block_start_pfn, block_end_pfn, cc->zone)) break; isolated = isolate_freepages_block(cc, &isolate_start_pfn, block_end_pfn, &freelist, true); /* * In strict mode, isolate_freepages_block() returns 0 if * there are any holes in the block (ie. invalid PFNs or * non-free pages). */ if (!isolated) break; /* * If we managed to isolate pages, it is always (1 << n) * * pageblock_nr_pages for some non-negative n. (Max order * page may span two pageblocks). */ } /* __isolate_free_page() does not map the pages */ map_pages(&freelist); if (pfn < end_pfn) { /* Loop terminated early, cleanup. */ release_freepages(&freelist); return 0; } /* We don't use freelists for anything. */ return pfn; } /* 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 = node_page_state(zone->zone_pgdat, NR_INACTIVE_FILE) + node_page_state(zone->zone_pgdat, NR_INACTIVE_ANON); active = node_page_state(zone->zone_pgdat, NR_ACTIVE_FILE) + node_page_state(zone->zone_pgdat, NR_ACTIVE_ANON); isolated = node_page_state(zone->zone_pgdat, NR_ISOLATED_FILE) + node_page_state(zone->zone_pgdat, NR_ISOLATED_ANON); return isolated > (inactive + active) / 2; } /** * isolate_migratepages_block() - isolate all migrate-able pages within * a single pageblock * @cc: Compaction control structure. * @low_pfn: The first PFN to isolate * @end_pfn: The one-past-the-last PFN to isolate, within same pageblock * @isolate_mode: Isolation mode to be used. * * Isolate all pages that can be migrated from the range specified by * [low_pfn, end_pfn). The range is expected to be within same pageblock. * Returns zero if there is a fatal signal pending, otherwise PFN of the * first page that was not scanned (which may be both less, equal to or more * than end_pfn). * * The pages are isolated on cc->migratepages list (not required to be empty), * and cc->nr_migratepages is updated accordingly. The cc->migrate_pfn field * is neither read nor updated. */ static unsigned long isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, unsigned long end_pfn, isolate_mode_t isolate_mode) { struct zone *zone = cc->zone; unsigned long nr_scanned = 0, nr_isolated = 0; struct lruvec *lruvec; unsigned long flags = 0; bool locked = false; struct page *page = NULL, *valid_page = NULL; unsigned long start_pfn = low_pfn; bool skip_on_failure = false; unsigned long next_skip_pfn = 0; /* * 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->mode == MIGRATE_ASYNC) return 0; congestion_wait(BLK_RW_ASYNC, HZ/10); if (fatal_signal_pending(current)) return 0; } if (compact_should_abort(cc)) return 0; if (cc->direct_compaction && (cc->mode == MIGRATE_ASYNC)) { skip_on_failure = true; next_skip_pfn = block_end_pfn(low_pfn, cc->order); } /* Time to isolate some pages for migration */ for (; low_pfn < end_pfn; low_pfn++) { if (skip_on_failure && low_pfn >= next_skip_pfn) { /* * We have isolated all migration candidates in the * previous order-aligned block, and did not skip it due * to failure. We should migrate the pages now and * hopefully succeed compaction. */ if (nr_isolated) break; /* * We failed to isolate in the previous order-aligned * block. Set the new boundary to the end of the * current block. Note we can't simply increase * next_skip_pfn by 1 << order, as low_pfn might have * been incremented by a higher number due to skipping * a compound or a high-order buddy page in the * previous loop iteration. */ next_skip_pfn = block_end_pfn(low_pfn, cc->order); } /* * Periodically drop the lock (if held) regardless of its * contention, to give chance to IRQs. Abort async compaction * if contended. */ if (!(low_pfn % SWAP_CLUSTER_MAX) && compact_unlock_should_abort(zone_lru_lock(zone), flags, &locked, cc)) break; if (!pfn_valid_within(low_pfn)) goto isolate_fail; nr_scanned++; page = pfn_to_page(low_pfn); if (!valid_page) valid_page = page; /* * Skip if free. We read page order here without zone lock * which is generally unsafe, but the race window is small and * the worst thing that can happen is that we skip some * potential isolation targets. */ if (PageBuddy(page)) { unsigned long freepage_order = page_order_unsafe(page); /* * Without lock, we cannot be sure that what we got is * a valid page order. Consider only values in the * valid order range to prevent low_pfn overflow. */ if (freepage_order > 0 && freepage_order < MAX_ORDER) low_pfn += (1UL << freepage_order) - 1; continue; } /* * Regardless of being on LRU, compound pages such as THP and * hugetlbfs are not to be compacted. We can potentially save * a lot of iterations if we skip them at once. The check is * racy, but we can consider only valid values and the only * danger is skipping too much. */ if (PageCompound(page)) { unsigned int comp_order = compound_order(page); if (likely(comp_order < MAX_ORDER)) low_pfn += (1UL << comp_order) - 1; goto isolate_fail; } /* * Check may be lockless but that's ok as we recheck later. * It's possible to migrate LRU and non-lru movable pages. * Skip any other type of page */ if (!PageLRU(page)) { /* * __PageMovable can return false positive so we need * to verify it under page_lock. */ if (unlikely(__PageMovable(page)) && !PageIsolated(page)) { if (locked) { spin_unlock_irqrestore(zone_lru_lock(zone), flags); locked = false; } if (!isolate_movable_page(page, isolate_mode)) goto isolate_success; } goto isolate_fail; } /* * Migration will fail if an anonymous page is pinned in memory, * so avoid taking lru_lock and isolating it unnecessarily in an * admittedly racy check. */ if (!page_mapping(page) && page_count(page) > page_mapcount(page)) goto isolate_fail; /* * Only allow to migrate anonymous pages in GFP_NOFS context * because those do not depend on fs locks. */ if (!(cc->gfp_mask & __GFP_FS) && page_mapping(page)) goto isolate_fail; /* If we already hold the lock, we can skip some rechecking */ if (!locked) { locked = compact_trylock_irqsave(zone_lru_lock(zone), &flags, cc); if (!locked) break; /* Recheck PageLRU and PageCompound under lock */ if (!PageLRU(page)) goto isolate_fail; /* * Page become compound since the non-locked check, * and it's on LRU. It can only be a THP so the order * is safe to read and it's 0 for tail pages. */ if (unlikely(PageCompound(page))) { low_pfn += (1UL << compound_order(page)) - 1; goto isolate_fail; } } lruvec = mem_cgroup_page_lruvec(page, zone->zone_pgdat); /* Try isolate the page */ if (__isolate_lru_page(page, isolate_mode) != 0) goto isolate_fail; VM_BUG_ON_PAGE(PageCompound(page), page); /* Successfully isolated */ del_page_from_lru_list(page, lruvec, page_lru(page)); inc_node_page_state(page, NR_ISOLATED_ANON + page_is_file_cache(page)); isolate_success: list_add(&page->lru, &cc->migratepages); cc->nr_migratepages++; nr_isolated++; /* * Record where we could have freed pages by migration and not * yet flushed them to buddy allocator. * - this is the lowest page that was isolated and likely be * then freed by migration. */ if (!cc->last_migrated_pfn) cc->last_migrated_pfn = low_pfn; /* Avoid isolating too much */ if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) { ++low_pfn; break; } continue; isolate_fail: if (!skip_on_failure) continue; /* * We have isolated some pages, but then failed. Release them * instead of migrating, as we cannot form the cc->order buddy * page anyway. */ if (nr_isolated) { if (locked) { spin_unlock_irqrestore(zone_lru_lock(zone), flags); locked = false; } putback_movable_pages(&cc->migratepages); cc->nr_migratepages = 0; cc->last_migrated_pfn = 0; nr_isolated = 0; } if (low_pfn < next_skip_pfn) { low_pfn = next_skip_pfn - 1; /* * The check near the loop beginning would have updated * next_skip_pfn too, but this is a bit simpler. */ next_skip_pfn += 1UL << cc->order; } } /* * The PageBuddy() check could have potentially brought us outside * the range to be scanned. */ if (unlikely(low_pfn > end_pfn)) low_pfn = end_pfn; if (locked) spin_unlock_irqrestore(zone_lru_lock(zone), flags); /* * Update the pageblock-skip information and cached scanner pfn, * if the whole pageblock was scanned without isolating any page. */ if (low_pfn == end_pfn) update_pageblock_skip(cc, valid_page, nr_isolated, true); trace_mm_compaction_isolate_migratepages(start_pfn, low_pfn, nr_scanned, nr_isolated); cc->total_migrate_scanned += nr_scanned; if (nr_isolated) count_compact_events(COMPACTISOLATED, nr_isolated); return low_pfn; } /** * isolate_migratepages_range() - isolate migrate-able pages in a PFN range * @cc: Compaction control structure. * @start_pfn: The first PFN to start isolating. * @end_pfn: The one-past-last PFN. * * Returns zero if isolation fails fatally due to e.g. pending signal. * Otherwise, function returns one-past-the-last PFN of isolated page * (which may be greater than end_pfn if end fell in a middle of a THP page). */ unsigned long isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn, unsigned long end_pfn) { unsigned long pfn, block_start_pfn, block_end_pfn; /* Scan block by block. First and last block may be incomplete */ pfn = start_pfn; block_start_pfn = pageblock_start_pfn(pfn); if (block_start_pfn < cc->zone->zone_start_pfn) block_start_pfn = cc->zone->zone_start_pfn; block_end_pfn = pageblock_end_pfn(pfn); for (; pfn < end_pfn; pfn = block_end_pfn, block_start_pfn = block_end_pfn, block_end_pfn += pageblock_nr_pages) { block_end_pfn = min(block_end_pfn, end_pfn); if (!pageblock_pfn_to_page(block_start_pfn, block_end_pfn, cc->zone)) continue; pfn = isolate_migratepages_block(cc, pfn, block_end_pfn, ISOLATE_UNEVICTABLE); if (!pfn) break; if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) break; } return pfn; } #endif /* CONFIG_COMPACTION || CONFIG_CMA */ #ifdef CONFIG_COMPACTION /* Returns true if the page is within a block suitable for migration to */ static bool suitable_migration_target(struct compact_control *cc, struct page *page) { if (cc->ignore_block_suitable) return true; /* If the page is a large free page, then disallow migration */ if (PageBuddy(page)) { /* * We are checking page_order without zone->lock taken. But * the only small danger is that we skip a potentially suitable * pageblock, so it's not worth to check order for valid range. */ if (page_order_unsafe(page) >= pageblock_order) return false; } /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */ if (migrate_async_suitable(get_pageblock_migratetype(page))) return true; /* Otherwise skip the block */ return false; } /* * Test whether the free scanner has reached the same or lower pageblock than * the migration scanner, and compaction should thus terminate. */ static inline bool compact_scanners_met(struct compact_control *cc) { return (cc->free_pfn >> pageblock_order) <= (cc->migrate_pfn >> pageblock_order); } /* * 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 compact_control *cc) { struct zone *zone = cc->zone; struct page *page; unsigned long block_start_pfn; /* start of current pageblock */ unsigned long isolate_start_pfn; /* exact pfn we start at */ unsigned long block_end_pfn; /* end of current pageblock */ unsigned long low_pfn; /* lowest pfn scanner is able to scan */ struct list_head *freelist = &cc->freepages; /* * Initialise the free scanner. The starting point is where we last * successfully isolated from, zone-cached value, or the end of the * zone when isolating for the first time. For looping we also need * this pfn aligned down to the pageblock boundary, because we do * block_start_pfn -= pageblock_nr_pages in the for loop. * For ending point, take care when isolating in last pageblock of a * a zone which ends in the middle of a pageblock. * The low boundary is the end of the pageblock the migration scanner * is using. */ isolate_start_pfn = cc->free_pfn; block_start_pfn = pageblock_start_pfn(cc->free_pfn); block_end_pfn = min(block_start_pfn + pageblock_nr_pages, zone_end_pfn(zone)); low_pfn = pageblock_end_pfn(cc->migrate_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 (; block_start_pfn >= low_pfn; block_end_pfn = block_start_pfn, block_start_pfn -= pageblock_nr_pages, isolate_start_pfn = block_start_pfn) { /* * This can iterate a massively long zone without finding any * suitable migration targets, so periodically check if we need * to schedule, or even abort async compaction. */ if (!(block_start_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages)) && compact_should_abort(cc)) break; page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn, zone); if (!page) continue; /* Check the block is suitable for migration */ if (!suitable_migration_target(cc, page)) continue; /* If isolation recently failed, do not retry */ if (!isolation_suitable(cc, page)) continue; /* Found a block suitable for isolating free pages from. */ isolate_freepages_block(cc, &isolate_start_pfn, block_end_pfn, freelist, false); /* * If we isolated enough freepages, or aborted due to lock * contention, terminate. */ if ((cc->nr_freepages >= cc->nr_migratepages) || cc->contended) { if (isolate_start_pfn >= block_end_pfn) { /* * Restart at previous pageblock if more * freepages can be isolated next time. */ isolate_start_pfn = block_start_pfn - pageblock_nr_pages; } break; } else if (isolate_start_pfn < block_end_pfn) { /* * If isolation failed early, do not continue * needlessly. */ break; } } /* __isolate_free_page() does not map the pages */ map_pages(freelist); /* * Record where the free scanner will restart next time. Either we * broke from the loop and set isolate_start_pfn based on the last * call to isolate_freepages_block(), or we met the migration scanner * and the loop terminated due to isolate_start_pfn < low_pfn */ cc->free_pfn = isolate_start_pfn; } /* * 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, and if we are not aborting due to * contention. */ if (list_empty(&cc->freepages)) { if (!cc->contended) isolate_freepages(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; } /* * This is a migrate-callback that "frees" freepages back to the isolated * freelist. All pages on the freelist are from the same zone, so there is no * special handling needed for NUMA. */ static void compaction_free(struct page *page, unsigned long data) { struct compact_control *cc = (struct compact_control *)data; list_add(&page->lru, &cc->freepages); cc->nr_freepages++; } /* 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; /* * Allow userspace to control policy on scanning the unevictable LRU for * compactable pages. */ int sysctl_compact_unevictable_allowed __read_mostly = 1; /* * Isolate all pages that can be migrated from the first suitable block, * starting at the block pointed to by the migrate scanner pfn within * compact_control. */ static isolate_migrate_t isolate_migratepages(struct zone *zone, struct compact_control *cc) { unsigned long block_start_pfn; unsigned long block_end_pfn; unsigned long low_pfn; struct page *page; const isolate_mode_t isolate_mode = (sysctl_compact_unevictable_allowed ? ISOLATE_UNEVICTABLE : 0) | (cc->mode != MIGRATE_SYNC ? ISOLATE_ASYNC_MIGRATE : 0); /* * Start at where we last stopped, or beginning of the zone as * initialized by compact_zone() */ low_pfn = cc->migrate_pfn; block_start_pfn = pageblock_start_pfn(low_pfn); if (block_start_pfn < zone->zone_start_pfn) block_start_pfn = zone->zone_start_pfn; /* Only scan within a pageblock boundary */ block_end_pfn = pageblock_end_pfn(low_pfn); /* * Iterate over whole pageblocks until we find the first suitable. * Do not cross the free scanner. */ for (; block_end_pfn <= cc->free_pfn; low_pfn = block_end_pfn, block_start_pfn = block_end_pfn, block_end_pfn += pageblock_nr_pages) { /* * This can potentially iterate a massively long zone with * many pageblocks unsuitable, so periodically check if we * need to schedule, or even abort async compaction. */ if (!(low_pfn % (SWAP_CLUSTER_MAX * pageblock_nr_pages)) && compact_should_abort(cc)) break; page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn, zone); if (!page) continue; /* If isolation recently failed, do not retry */ if (!isolation_suitable(cc, page)) continue; /* * For async compaction, also only scan in MOVABLE blocks. * Async compaction is optimistic to see if the minimum amount * of work satisfies the allocation. */ if (cc->mode == MIGRATE_ASYNC && !migrate_async_suitable(get_pageblock_migratetype(page))) continue; /* Perform the isolation */ low_pfn = isolate_migratepages_block(cc, low_pfn, block_end_pfn, isolate_mode); if (!low_pfn || cc->contended) return ISOLATE_ABORT; /* * Either we isolated something and proceed with migration. Or * we failed and compact_zone should decide if we should * continue or not. */ break; } /* Record where migration scanner will be restarted. */ cc->migrate_pfn = low_pfn; return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE; } /* * order == -1 is expected when compacting via * /proc/sys/vm/compact_memory */ static inline bool is_via_compact_memory(int order) { return order == -1; } static enum compact_result __compact_finished(struct zone *zone, struct compact_control *cc, const int migratetype) { unsigned int order; unsigned long watermark; if (cc->contended || fatal_signal_pending(current)) return COMPACT_CONTENDED; /* Compaction run completes if the migrate and free scanner meet */ if (compact_scanners_met(cc)) { /* Let the next compaction start anew. */ reset_cached_positions(zone); /* * Mark that the PG_migrate_skip information should be cleared * by kswapd when it goes to sleep. kcompactd does not set the * flag itself as the decision to be clear should be directly * based on an allocation request. */ if (cc->direct_compaction) zone->compact_blockskip_flush = true; if (cc->whole_zone) return COMPACT_COMPLETE; else return COMPACT_PARTIAL_SKIPPED; } if (is_via_compact_memory(cc->order)) return COMPACT_CONTINUE; /* Compaction run is not finished if the watermark is not met */ watermark = zone->watermark[cc->alloc_flags & ALLOC_WMARK_MASK]; if (!zone_watermark_ok(zone, cc->order, watermark, cc->classzone_idx, cc->alloc_flags)) return COMPACT_CONTINUE; /* Direct compactor: Is a suitable page free? */ for (order = cc->order; order < MAX_ORDER; order++) { struct free_area *area = &zone->free_area[order]; bool can_steal; /* Job done if page is free of the right migratetype */ if (!list_empty(&area->free_list[migratetype])) return COMPACT_SUCCESS; #ifdef CONFIG_CMA /* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */ if (migratetype == MIGRATE_MOVABLE && !list_empty(&area->free_list[MIGRATE_CMA])) return COMPACT_SUCCESS; #endif /* * Job done if allocation would steal freepages from * other migratetype buddy lists. */ if (find_suitable_fallback(area, order, migratetype, true, &can_steal) != -1) return COMPACT_SUCCESS; } return COMPACT_NO_SUITABLE_PAGE; } static enum compact_result compact_finished(struct zone *zone, struct compact_control *cc, const int migratetype) { int ret; ret = __compact_finished(zone, cc, migratetype); trace_mm_compaction_finished(zone, cc->order, ret); if (ret == COMPACT_NO_SUITABLE_PAGE) ret = COMPACT_CONTINUE; return ret; } /* * 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_SUCCESS - If the allocation would succeed without compaction * COMPACT_CONTINUE - If compaction should run now */ static enum compact_result __compaction_suitable(struct zone *zone, int order, unsigned int alloc_flags, int classzone_idx, unsigned long wmark_target) { unsigned long watermark; if (is_via_compact_memory(order)) return COMPACT_CONTINUE; watermark = zone->watermark[alloc_flags & ALLOC_WMARK_MASK]; /* * If watermarks for high-order allocation are already met, there * should be no need for compaction at all. */ if (zone_watermark_ok(zone, order, watermark, classzone_idx, alloc_flags)) return COMPACT_SUCCESS; /* * Watermarks for order-0 must be met for compaction to be able to * isolate free pages for migration targets. This means that the * watermark and alloc_flags have to match, or be more pessimistic than * the check in __isolate_free_page(). We don't use the direct * compactor's alloc_flags, as they are not relevant for freepage * isolation. We however do use the direct compactor's classzone_idx to * skip over zones where lowmem reserves would prevent allocation even * if compaction succeeds. * For costly orders, we require low watermark instead of min for * compaction to proceed to increase its chances. * ALLOC_CMA is used, as pages in CMA pageblocks are considered * suitable migration targets */ watermark = (order > PAGE_ALLOC_COSTLY_ORDER) ? low_wmark_pages(zone) : min_wmark_pages(zone); watermark += compact_gap(order); if (!__zone_watermark_ok(zone, 0, watermark, classzone_idx, ALLOC_CMA, wmark_target)) return COMPACT_SKIPPED; return COMPACT_CONTINUE; } enum compact_result compaction_suitable(struct zone *zone, int order, unsigned int alloc_flags, int classzone_idx) { enum compact_result ret; int fragindex; ret = __compaction_suitable(zone, order, alloc_flags, classzone_idx, zone_page_state(zone, NR_FREE_PAGES)); /* * fragmentation index determines if allocation failures are due to * low memory or external fragmentation * * index of -1000 would imply allocations might succeed depending on * watermarks, but we already failed the high-order watermark check * index towards 0 implies failure is due to lack of memory * index towards 1000 implies failure is due to fragmentation * * Only compact if a failure would be due to fragmentation. Also * ignore fragindex for non-costly orders where the alternative to * a successful reclaim/compaction is OOM. Fragindex and the * vm.extfrag_threshold sysctl is meant as a heuristic to prevent * excessive compaction for costly orders, but it should not be at the * expense of system stability. */ if (ret == COMPACT_CONTINUE && (order > PAGE_ALLOC_COSTLY_ORDER)) { fragindex = fragmentation_index(zone, order); if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold) ret = COMPACT_NOT_SUITABLE_ZONE; } trace_mm_compaction_suitable(zone, order, ret); if (ret == COMPACT_NOT_SUITABLE_ZONE) ret = COMPACT_SKIPPED; return ret; } bool compaction_zonelist_suitable(struct alloc_context *ac, int order, int alloc_flags) { struct zone *zone; struct zoneref *z; /* * Make sure at least one zone would pass __compaction_suitable if we continue * retrying the reclaim. */ for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx, ac->nodemask) { unsigned long available; enum compact_result compact_result; /* * Do not consider all the reclaimable memory because we do not * want to trash just for a single high order allocation which * is even not guaranteed to appear even if __compaction_suitable * is happy about the watermark check. */ available = zone_reclaimable_pages(zone) / order; available += zone_page_state_snapshot(zone, NR_FREE_PAGES); compact_result = __compaction_suitable(zone, order, alloc_flags, ac_classzone_idx(ac), available); if (compact_result != COMPACT_SKIPPED) return true; } return false; } static enum compact_result compact_zone(struct zone *zone, struct compact_control *cc) { enum compact_result ret; unsigned long start_pfn = zone->zone_start_pfn; unsigned long end_pfn = zone_end_pfn(zone); const int migratetype = gfpflags_to_migratetype(cc->gfp_mask); const bool sync = cc->mode != MIGRATE_ASYNC; ret = compaction_suitable(zone, cc->order, cc->alloc_flags, cc->classzone_idx); /* Compaction is likely to fail */ if (ret == COMPACT_SUCCESS || ret == COMPACT_SKIPPED) return ret; /* huh, compaction_suitable is returning something unexpected */ VM_BUG_ON(ret != COMPACT_CONTINUE); /* * Clear pageblock skip if there were failures recently and compaction * is about to be retried after being deferred. */ if (compaction_restarting(zone, cc->order)) __reset_isolation_suitable(zone); /* * Setup to move all movable pages to the end of the zone. Used cached * information on where the scanners should start (unless we explicitly * want to compact the whole zone), but check that it is initialised * by ensuring the values are within zone boundaries. */ if (cc->whole_zone) { cc->migrate_pfn = start_pfn; cc->free_pfn = pageblock_start_pfn(end_pfn - 1); } else { cc->migrate_pfn = zone->compact_cached_migrate_pfn[sync]; cc->free_pfn = zone->compact_cached_free_pfn; if (cc->free_pfn < start_pfn || cc->free_pfn >= end_pfn) { cc->free_pfn = pageblock_start_pfn(end_pfn - 1); zone->compact_cached_free_pfn = cc->free_pfn; } if (cc->migrate_pfn < start_pfn || cc->migrate_pfn >= end_pfn) { cc->migrate_pfn = start_pfn; zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn; zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn; } if (cc->migrate_pfn == start_pfn) cc->whole_zone = true; } cc->last_migrated_pfn = 0; trace_mm_compaction_begin(start_pfn, cc->migrate_pfn, cc->free_pfn, end_pfn, sync); migrate_prep_local(); while ((ret = compact_finished(zone, cc, migratetype)) == COMPACT_CONTINUE) { int err; switch (isolate_migratepages(zone, cc)) { case ISOLATE_ABORT: ret = COMPACT_CONTENDED; putback_movable_pages(&cc->migratepages); cc->nr_migratepages = 0; goto out; case ISOLATE_NONE: /* * We haven't isolated and migrated anything, but * there might still be unflushed migrations from * previous cc->order aligned block. */ goto check_drain; case ISOLATE_SUCCESS: ; } err = migrate_pages(&cc->migratepages, compaction_alloc, compaction_free, (unsigned long)cc, cc->mode, MR_COMPACTION); trace_mm_compaction_migratepages(cc->nr_migratepages, err, &cc->migratepages); /* All pages were either migrated or will be released */ cc->nr_migratepages = 0; if (err) { putback_movable_pages(&cc->migratepages); /* * migrate_pages() may return -ENOMEM when scanners meet * and we want compact_finished() to detect it */ if (err == -ENOMEM && !compact_scanners_met(cc)) { ret = COMPACT_CONTENDED; goto out; } /* * We failed to migrate at least one page in the current * order-aligned block, so skip the rest of it. */ if (cc->direct_compaction && (cc->mode == MIGRATE_ASYNC)) { cc->migrate_pfn = block_end_pfn( cc->migrate_pfn - 1, cc->order); /* Draining pcplists is useless in this case */ cc->last_migrated_pfn = 0; } } check_drain: /* * Has the migration scanner moved away from the previous * cc->order aligned block where we migrated from? If yes, * flush the pages that were freed, so that they can merge and * compact_finished() can detect immediately if allocation * would succeed. */ if (cc->order > 0 && cc->last_migrated_pfn) { int cpu; unsigned long current_block_start = block_start_pfn(cc->migrate_pfn, cc->order); if (cc->last_migrated_pfn < current_block_start) { cpu = get_cpu(); lru_add_drain_cpu(cpu); drain_local_pages(zone); put_cpu(); /* No more flushing until we migrate again */ cc->last_migrated_pfn = 0; } } } out: /* * Release free pages and update where the free scanner should restart, * so we don't leave any returned pages behind in the next attempt. */ if (cc->nr_freepages > 0) { unsigned long free_pfn = release_freepages(&cc->freepages); cc->nr_freepages = 0; VM_BUG_ON(free_pfn == 0); /* The cached pfn is always the first in a pageblock */ free_pfn = pageblock_start_pfn(free_pfn); /* * Only go back, not forward. The cached pfn might have been * already reset to zone end in compact_finished() */ if (free_pfn > zone->compact_cached_free_pfn) zone->compact_cached_free_pfn = free_pfn; } count_compact_events(COMPACTMIGRATE_SCANNED, cc->total_migrate_scanned); count_compact_events(COMPACTFREE_SCANNED, cc->total_free_scanned); trace_mm_compaction_end(start_pfn, cc->migrate_pfn, cc->free_pfn, end_pfn, sync, ret); return ret; } static enum compact_result compact_zone_order(struct zone *zone, int order, gfp_t gfp_mask, enum compact_priority prio, unsigned int alloc_flags, int classzone_idx) { enum compact_result ret; struct compact_control cc = { .nr_freepages = 0, .nr_migratepages = 0, .total_migrate_scanned = 0, .total_free_scanned = 0, .order = order, .gfp_mask = gfp_mask, .zone = zone, .mode = (prio == COMPACT_PRIO_ASYNC) ? MIGRATE_ASYNC : MIGRATE_SYNC_LIGHT, .alloc_flags = alloc_flags, .classzone_idx = classzone_idx, .direct_compaction = true, .whole_zone = (prio == MIN_COMPACT_PRIORITY), .ignore_skip_hint = (prio == MIN_COMPACT_PRIORITY), .ignore_block_suitable = (prio == MIN_COMPACT_PRIORITY) }; INIT_LIST_HEAD(&cc.freepages); INIT_LIST_HEAD(&cc.migratepages); ret = compact_zone(zone, &cc); VM_BUG_ON(!list_empty(&cc.freepages)); VM_BUG_ON(!list_empty(&cc.migratepages)); return ret; } int sysctl_extfrag_threshold = 500; /** * try_to_compact_pages - Direct compact to satisfy a high-order allocation * @gfp_mask: The GFP mask of the current allocation * @order: The order of the current allocation * @alloc_flags: The allocation flags of the current allocation * @ac: The context of current allocation * @mode: The migration mode for async, sync light, or sync migration * * This is the main entry point for direct page compaction. */ enum compact_result try_to_compact_pages(gfp_t gfp_mask, unsigned int order, unsigned int alloc_flags, const struct alloc_context *ac, enum compact_priority prio) { int may_perform_io = gfp_mask & __GFP_IO; struct zoneref *z; struct zone *zone; enum compact_result rc = COMPACT_SKIPPED; /* * Check if the GFP flags allow compaction - GFP_NOIO is really * tricky context because the migration might require IO */ if (!may_perform_io) return COMPACT_SKIPPED; trace_mm_compaction_try_to_compact_pages(order, gfp_mask, prio); /* Compact each zone in the list */ for_each_zone_zonelist_nodemask(zone, z, ac->zonelist, ac->high_zoneidx, ac->nodemask) { enum compact_result status; if (prio > MIN_COMPACT_PRIORITY && compaction_deferred(zone, order)) { rc = max_t(enum compact_result, COMPACT_DEFERRED, rc); continue; } status = compact_zone_order(zone, order, gfp_mask, prio, alloc_flags, ac_classzone_idx(ac)); rc = max(status, rc); /* The allocation should succeed, stop compacting */ if (status == COMPACT_SUCCESS) { /* * We think the allocation will succeed in this zone, * but it is not certain, hence the false. The caller * will repeat this with true if allocation indeed * succeeds in this zone. */ compaction_defer_reset(zone, order, false); break; } if (prio != COMPACT_PRIO_ASYNC && (status == COMPACT_COMPLETE || status == COMPACT_PARTIAL_SKIPPED)) /* * We think that allocation won't succeed in this zone * so we defer compaction there. If it ends up * succeeding after all, it will be reset. */ defer_compaction(zone, order); /* * We might have stopped compacting due to need_resched() in * async compaction, or due to a fatal signal detected. In that * case do not try further zones */ if ((prio == COMPACT_PRIO_ASYNC && need_resched()) || fatal_signal_pending(current)) break; } return rc; } /* Compact all zones within a node */ static void compact_node(int nid) { pg_data_t *pgdat = NODE_DATA(nid); int zoneid; struct zone *zone; struct compact_control cc = { .order = -1, .total_migrate_scanned = 0, .total_free_scanned = 0, .mode = MIGRATE_SYNC, .ignore_skip_hint = true, .whole_zone = true, .gfp_mask = GFP_KERNEL, }; for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { zone = &pgdat->node_zones[zoneid]; if (!populated_zone(zone)) continue; cc.nr_freepages = 0; cc.nr_migratepages = 0; cc.zone = zone; INIT_LIST_HEAD(&cc.freepages); INIT_LIST_HEAD(&cc.migratepages); compact_zone(zone, &cc); VM_BUG_ON(!list_empty(&cc.freepages)); VM_BUG_ON(!list_empty(&cc.migratepages)); } } /* Compact all nodes in the system */ static void compact_nodes(void) { int nid; /* Flush pending updates to the LRU lists */ lru_add_drain_all(); for_each_online_node(nid) compact_node(nid); } /* The written value is actually unused, all memory is compacted */ int sysctl_compact_memory; /* * This is the entry point for compacting all nodes via * /proc/sys/vm/compact_memory */ int sysctl_compaction_handler(struct ctl_table *table, int write, void __user *buffer, size_t *length, loff_t *ppos) { if (write) compact_nodes(); return 0; } int sysctl_extfrag_handler(struct ctl_table *table, int write, void __user *buffer, size_t *length, loff_t *ppos) { proc_dointvec_minmax(table, write, buffer, length, ppos); return 0; } #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA) static ssize_t sysfs_compact_node(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { int nid = dev->id; if (nid >= 0 && nid < nr_node_ids && node_online(nid)) { /* Flush pending updates to the LRU lists */ lru_add_drain_all(); compact_node(nid); } return count; } static DEVICE_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node); int compaction_register_node(struct node *node) { return device_create_file(&node->dev, &dev_attr_compact); } void compaction_unregister_node(struct node *node) { return device_remove_file(&node->dev, &dev_attr_compact); } #endif /* CONFIG_SYSFS && CONFIG_NUMA */ static inline bool kcompactd_work_requested(pg_data_t *pgdat) { return pgdat->kcompactd_max_order > 0 || kthread_should_stop(); } static bool kcompactd_node_suitable(pg_data_t *pgdat) { int zoneid; struct zone *zone; enum zone_type classzone_idx = pgdat->kcompactd_classzone_idx; for (zoneid = 0; zoneid <= classzone_idx; zoneid++) { zone = &pgdat->node_zones[zoneid]; if (!populated_zone(zone)) continue; if (compaction_suitable(zone, pgdat->kcompactd_max_order, 0, classzone_idx) == COMPACT_CONTINUE) return true; } return false; } static void kcompactd_do_work(pg_data_t *pgdat) { /* * With no special task, compact all zones so that a page of requested * order is allocatable. */ int zoneid; struct zone *zone; struct compact_control cc = { .order = pgdat->kcompactd_max_order, .total_migrate_scanned = 0, .total_free_scanned = 0, .classzone_idx = pgdat->kcompactd_classzone_idx, .mode = MIGRATE_SYNC_LIGHT, .ignore_skip_hint = true, .gfp_mask = GFP_KERNEL, }; trace_mm_compaction_kcompactd_wake(pgdat->node_id, cc.order, cc.classzone_idx); count_compact_event(KCOMPACTD_WAKE); for (zoneid = 0; zoneid <= cc.classzone_idx; zoneid++) { int status; zone = &pgdat->node_zones[zoneid]; if (!populated_zone(zone)) continue; if (compaction_deferred(zone, cc.order)) continue; if (compaction_suitable(zone, cc.order, 0, zoneid) != COMPACT_CONTINUE) continue; cc.nr_freepages = 0; cc.nr_migratepages = 0; cc.total_migrate_scanned = 0; cc.total_free_scanned = 0; cc.zone = zone; INIT_LIST_HEAD(&cc.freepages); INIT_LIST_HEAD(&cc.migratepages); if (kthread_should_stop()) return; status = compact_zone(zone, &cc); if (status == COMPACT_SUCCESS) { compaction_defer_reset(zone, cc.order, false); } else if (status == COMPACT_PARTIAL_SKIPPED || status == COMPACT_COMPLETE) { /* * We use sync migration mode here, so we defer like * sync direct compaction does. */ defer_compaction(zone, cc.order); } count_compact_events(KCOMPACTD_MIGRATE_SCANNED, cc.total_migrate_scanned); count_compact_events(KCOMPACTD_FREE_SCANNED, cc.total_free_scanned); VM_BUG_ON(!list_empty(&cc.freepages)); VM_BUG_ON(!list_empty(&cc.migratepages)); } /* * Regardless of success, we are done until woken up next. But remember * the requested order/classzone_idx in case it was higher/tighter than * our current ones */ if (pgdat->kcompactd_max_order <= cc.order) pgdat->kcompactd_max_order = 0; if (pgdat->kcompactd_classzone_idx >= cc.classzone_idx) pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1; } void wakeup_kcompactd(pg_data_t *pgdat, int order, int classzone_idx) { if (!order) return; if (pgdat->kcompactd_max_order < order) pgdat->kcompactd_max_order = order; /* * Pairs with implicit barrier in wait_event_freezable() * such that wakeups are not missed in the lockless * waitqueue_active() call. */ smp_acquire__after_ctrl_dep(); if (pgdat->kcompactd_classzone_idx > classzone_idx) pgdat->kcompactd_classzone_idx = classzone_idx; if (!waitqueue_active(&pgdat->kcompactd_wait)) return; if (!kcompactd_node_suitable(pgdat)) return; trace_mm_compaction_wakeup_kcompactd(pgdat->node_id, order, classzone_idx); wake_up_interruptible(&pgdat->kcompactd_wait); } /* * The background compaction daemon, started as a kernel thread * from the init process. */ static int kcompactd(void *p) { pg_data_t *pgdat = (pg_data_t*)p; struct task_struct *tsk = current; const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); if (!cpumask_empty(cpumask)) set_cpus_allowed_ptr(tsk, cpumask); set_freezable(); pgdat->kcompactd_max_order = 0; pgdat->kcompactd_classzone_idx = pgdat->nr_zones - 1; while (!kthread_should_stop()) { trace_mm_compaction_kcompactd_sleep(pgdat->node_id); wait_event_freezable(pgdat->kcompactd_wait, kcompactd_work_requested(pgdat)); kcompactd_do_work(pgdat); } return 0; } /* * This kcompactd start function will be called by init and node-hot-add. * On node-hot-add, kcompactd will moved to proper cpus if cpus are hot-added. */ int kcompactd_run(int nid) { pg_data_t *pgdat = NODE_DATA(nid); int ret = 0; if (pgdat->kcompactd) return 0; pgdat->kcompactd = kthread_run(kcompactd, pgdat, "kcompactd%d", nid); if (IS_ERR(pgdat->kcompactd)) { pr_err("Failed to start kcompactd on node %d\n", nid); ret = PTR_ERR(pgdat->kcompactd); pgdat->kcompactd = NULL; } return ret; } /* * Called by memory hotplug when all memory in a node is offlined. Caller must * hold mem_hotplug_begin/end(). */ void kcompactd_stop(int nid) { struct task_struct *kcompactd = NODE_DATA(nid)->kcompactd; if (kcompactd) { kthread_stop(kcompactd); NODE_DATA(nid)->kcompactd = NULL; } } /* * It's optimal to keep kcompactd on the same CPUs as their memory, but * not required for correctness. So if the last cpu in a node goes * away, we get changed to run anywhere: as the first one comes back, * restore their cpu bindings. */ static int kcompactd_cpu_online(unsigned int cpu) { int nid; for_each_node_state(nid, N_MEMORY) { pg_data_t *pgdat = NODE_DATA(nid); const struct cpumask *mask; mask = cpumask_of_node(pgdat->node_id); if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) /* One of our CPUs online: restore mask */ set_cpus_allowed_ptr(pgdat->kcompactd, mask); } return 0; } static int __init kcompactd_init(void) { int nid; int ret; ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "mm/compaction:online", kcompactd_cpu_online, NULL); if (ret < 0) { pr_err("kcompactd: failed to register hotplug callbacks.\n"); return ret; } for_each_node_state(nid, N_MEMORY) kcompactd_run(nid); return 0; } subsys_initcall(kcompactd_init) #endif /* CONFIG_COMPACTION */