| // SPDX-License-Identifier: GPL-2.0 |
| /* |
| * 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 <linux/psi.h> |
| #include "internal.h" |
| |
| #ifdef CONFIG_COMPACTION |
| /* |
| * Fragmentation score check interval for proactive compaction purposes. |
| */ |
| #define HPAGE_FRAG_CHECK_INTERVAL_MSEC (500) |
| |
| 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); |
| } |
| |
| /* |
| * order == -1 is expected when compacting proactively via |
| * 1. /proc/sys/vm/compact_memory |
| * 2. /sys/devices/system/node/nodex/compact |
| * 3. /proc/sys/vm/compaction_proactiveness |
| */ |
| static inline bool is_via_compact_memory(int order) |
| { |
| return order == -1; |
| } |
| |
| #else |
| #define count_compact_event(item) do { } while (0) |
| #define count_compact_events(item, delta) do { } while (0) |
| static inline bool is_via_compact_memory(int order) { return false; } |
| #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)) |
| |
| /* |
| * Page order with-respect-to which proactive compaction |
| * calculates external fragmentation, which is used as |
| * the "fragmentation score" of a node/zone. |
| */ |
| #if defined CONFIG_TRANSPARENT_HUGEPAGE |
| #define COMPACTION_HPAGE_ORDER HPAGE_PMD_ORDER |
| #elif defined CONFIG_HUGETLBFS |
| #define COMPACTION_HPAGE_ORDER HUGETLB_PAGE_ORDER |
| #else |
| #define COMPACTION_HPAGE_ORDER (PMD_SHIFT - PAGE_SHIFT) |
| #endif |
| |
| static struct page *mark_allocated_noprof(struct page *page, unsigned int order, gfp_t gfp_flags) |
| { |
| post_alloc_hook(page, order, __GFP_MOVABLE); |
| return page; |
| } |
| #define mark_allocated(...) alloc_hooks(mark_allocated_noprof(__VA_ARGS__)) |
| |
| static void split_map_pages(struct list_head *freepages) |
| { |
| unsigned int i, order; |
| struct page *page, *next; |
| LIST_HEAD(tmp_list); |
| |
| for (order = 0; order < NR_PAGE_ORDERS; order++) { |
| list_for_each_entry_safe(page, next, &freepages[order], lru) { |
| unsigned int nr_pages; |
| |
| list_del(&page->lru); |
| |
| nr_pages = 1 << order; |
| |
| mark_allocated(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_init(&tmp_list, &freepages[0]); |
| } |
| } |
| |
| static unsigned long release_free_list(struct list_head *freepages) |
| { |
| int order; |
| unsigned long high_pfn = 0; |
| |
| for (order = 0; order < NR_PAGE_ORDERS; order++) { |
| struct page *page, *next; |
| |
| list_for_each_entry_safe(page, next, &freepages[order], lru) { |
| unsigned long pfn = page_to_pfn(page); |
| |
| list_del(&page->lru); |
| /* |
| * Convert free pages into post allocation pages, so |
| * that we can free them via __free_page. |
| */ |
| mark_allocated(page, order, __GFP_MOVABLE); |
| __free_pages(page, order); |
| if (pfn > high_pfn) |
| high_pfn = pfn; |
| } |
| } |
| return high_pfn; |
| } |
| |
| #ifdef CONFIG_COMPACTION |
| bool PageMovable(struct page *page) |
| { |
| const struct movable_operations *mops; |
| |
| VM_BUG_ON_PAGE(!PageLocked(page), page); |
| if (!__PageMovable(page)) |
| return false; |
| |
| mops = page_movable_ops(page); |
| if (mops) |
| return true; |
| |
| return false; |
| } |
| |
| void __SetPageMovable(struct page *page, const struct movable_operations *mops) |
| { |
| VM_BUG_ON_PAGE(!PageLocked(page), page); |
| VM_BUG_ON_PAGE((unsigned long)mops & PAGE_MAPPING_MOVABLE, page); |
| page->mapping = (void *)((unsigned long)mops | PAGE_MAPPING_MOVABLE); |
| } |
| EXPORT_SYMBOL(__SetPageMovable); |
| |
| void __ClearPageMovable(struct page *page) |
| { |
| VM_BUG_ON_PAGE(!PageMovable(page), page); |
| /* |
| * This page still has the type of a movable page, but it's |
| * actually not movable any more. |
| */ |
| page->mapping = (void *)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_shift, compactions are skipped up |
| * to a limit of 1 << COMPACT_MAX_DEFER_SHIFT |
| */ |
| static 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 */ |
| static 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; |
| 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 */ |
| static 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); |
| } |
| |
| #ifdef CONFIG_SPARSEMEM |
| /* |
| * If the PFN falls into an offline section, return the start PFN of the |
| * next online section. If the PFN falls into an online section or if |
| * there is no next online section, return 0. |
| */ |
| static unsigned long skip_offline_sections(unsigned long start_pfn) |
| { |
| unsigned long start_nr = pfn_to_section_nr(start_pfn); |
| |
| if (online_section_nr(start_nr)) |
| return 0; |
| |
| while (++start_nr <= __highest_present_section_nr) { |
| if (online_section_nr(start_nr)) |
| return section_nr_to_pfn(start_nr); |
| } |
| |
| return 0; |
| } |
| |
| /* |
| * If the PFN falls into an offline section, return the end PFN of the |
| * next online section in reverse. If the PFN falls into an online section |
| * or if there is no next online section in reverse, return 0. |
| */ |
| static unsigned long skip_offline_sections_reverse(unsigned long start_pfn) |
| { |
| unsigned long start_nr = pfn_to_section_nr(start_pfn); |
| |
| if (!start_nr || online_section_nr(start_nr)) |
| return 0; |
| |
| while (start_nr-- > 0) { |
| if (online_section_nr(start_nr)) |
| return section_nr_to_pfn(start_nr) + PAGES_PER_SECTION; |
| } |
| |
| return 0; |
| } |
| #else |
| static unsigned long skip_offline_sections(unsigned long start_pfn) |
| { |
| return 0; |
| } |
| |
| static unsigned long skip_offline_sections_reverse(unsigned long start_pfn) |
| { |
| return 0; |
| } |
| #endif |
| |
| /* |
| * Compound pages of >= pageblock_order should consistently be skipped until |
| * released. It is always pointless to compact pages of such order (if they are |
| * migratable), and the pageblocks they occupy cannot contain any free pages. |
| */ |
| static bool pageblock_skip_persistent(struct page *page) |
| { |
| if (!PageCompound(page)) |
| return false; |
| |
| page = compound_head(page); |
| |
| if (compound_order(page) >= pageblock_order) |
| return true; |
| |
| return false; |
| } |
| |
| static bool |
| __reset_isolation_pfn(struct zone *zone, unsigned long pfn, bool check_source, |
| bool check_target) |
| { |
| struct page *page = pfn_to_online_page(pfn); |
| struct page *block_page; |
| struct page *end_page; |
| unsigned long block_pfn; |
| |
| if (!page) |
| return false; |
| if (zone != page_zone(page)) |
| return false; |
| if (pageblock_skip_persistent(page)) |
| return false; |
| |
| /* |
| * If skip is already cleared do no further checking once the |
| * restart points have been set. |
| */ |
| if (check_source && check_target && !get_pageblock_skip(page)) |
| return true; |
| |
| /* |
| * If clearing skip for the target scanner, do not select a |
| * non-movable pageblock as the starting point. |
| */ |
| if (!check_source && check_target && |
| get_pageblock_migratetype(page) != MIGRATE_MOVABLE) |
| return false; |
| |
| /* Ensure the start of the pageblock or zone is online and valid */ |
| block_pfn = pageblock_start_pfn(pfn); |
| block_pfn = max(block_pfn, zone->zone_start_pfn); |
| block_page = pfn_to_online_page(block_pfn); |
| if (block_page) { |
| page = block_page; |
| pfn = block_pfn; |
| } |
| |
| /* Ensure the end of the pageblock or zone is online and valid */ |
| block_pfn = pageblock_end_pfn(pfn) - 1; |
| block_pfn = min(block_pfn, zone_end_pfn(zone) - 1); |
| end_page = pfn_to_online_page(block_pfn); |
| if (!end_page) |
| return false; |
| |
| /* |
| * Only clear the hint if a sample indicates there is either a |
| * free page or an LRU page in the block. One or other condition |
| * is necessary for the block to be a migration source/target. |
| */ |
| do { |
| if (check_source && PageLRU(page)) { |
| clear_pageblock_skip(page); |
| return true; |
| } |
| |
| if (check_target && PageBuddy(page)) { |
| clear_pageblock_skip(page); |
| return true; |
| } |
| |
| page += (1 << PAGE_ALLOC_COSTLY_ORDER); |
| } while (page <= end_page); |
| |
| return false; |
| } |
| |
| /* |
| * 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 migrate_pfn = zone->zone_start_pfn; |
| unsigned long free_pfn = zone_end_pfn(zone) - 1; |
| unsigned long reset_migrate = free_pfn; |
| unsigned long reset_free = migrate_pfn; |
| bool source_set = false; |
| bool free_set = false; |
| |
| /* Only flush if a full compaction finished recently */ |
| if (!zone->compact_blockskip_flush) |
| return; |
| |
| zone->compact_blockskip_flush = false; |
| |
| /* |
| * Walk the zone and update pageblock skip information. Source looks |
| * for PageLRU while target looks for PageBuddy. When the scanner |
| * is found, both PageBuddy and PageLRU are checked as the pageblock |
| * is suitable as both source and target. |
| */ |
| for (; migrate_pfn < free_pfn; migrate_pfn += pageblock_nr_pages, |
| free_pfn -= pageblock_nr_pages) { |
| cond_resched(); |
| |
| /* Update the migrate PFN */ |
| if (__reset_isolation_pfn(zone, migrate_pfn, true, source_set) && |
| migrate_pfn < reset_migrate) { |
| source_set = true; |
| reset_migrate = migrate_pfn; |
| zone->compact_init_migrate_pfn = reset_migrate; |
| zone->compact_cached_migrate_pfn[0] = reset_migrate; |
| zone->compact_cached_migrate_pfn[1] = reset_migrate; |
| } |
| |
| /* Update the free PFN */ |
| if (__reset_isolation_pfn(zone, free_pfn, free_set, true) && |
| free_pfn > reset_free) { |
| free_set = true; |
| reset_free = free_pfn; |
| zone->compact_init_free_pfn = reset_free; |
| zone->compact_cached_free_pfn = reset_free; |
| } |
| } |
| |
| /* Leave no distance if no suitable block was reset */ |
| if (reset_migrate >= reset_free) { |
| zone->compact_cached_migrate_pfn[0] = migrate_pfn; |
| zone->compact_cached_migrate_pfn[1] = migrate_pfn; |
| zone->compact_cached_free_pfn = free_pfn; |
| } |
| } |
| |
| 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; |
| |
| __reset_isolation_suitable(zone); |
| } |
| } |
| |
| /* |
| * Sets the pageblock skip bit if it was clear. Note that this is a hint as |
| * locks are not required for read/writers. Returns true if it was already set. |
| */ |
| static bool test_and_set_skip(struct compact_control *cc, struct page *page) |
| { |
| bool skip; |
| |
| /* Do not update if skip hint is being ignored */ |
| if (cc->ignore_skip_hint) |
| return false; |
| |
| skip = get_pageblock_skip(page); |
| if (!skip && !cc->no_set_skip_hint) |
| set_pageblock_skip(page); |
| |
| return skip; |
| } |
| |
| static void update_cached_migrate(struct compact_control *cc, unsigned long pfn) |
| { |
| struct zone *zone = cc->zone; |
| |
| /* Set for isolation rather than compaction */ |
| if (cc->no_set_skip_hint) |
| return; |
| |
| pfn = pageblock_end_pfn(pfn); |
| |
| /* Update where async and sync compaction should restart */ |
| 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; |
| } |
| |
| /* |
| * 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 pfn) |
| { |
| struct zone *zone = cc->zone; |
| |
| if (cc->no_set_skip_hint) |
| return; |
| |
| set_pageblock_skip(page); |
| |
| 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 inline bool pageblock_skip_persistent(struct page *page) |
| { |
| return false; |
| } |
| |
| static inline void update_pageblock_skip(struct compact_control *cc, |
| struct page *page, unsigned long pfn) |
| { |
| } |
| |
| static void update_cached_migrate(struct compact_control *cc, unsigned long pfn) |
| { |
| } |
| |
| static bool test_and_set_skip(struct compact_control *cc, struct page *page) |
| { |
| return false; |
| } |
| #endif /* CONFIG_COMPACTION */ |
| |
| /* |
| * Compaction requires the taking of some coarse locks that are potentially |
| * very heavily contended. For async compaction, trylock and record if the |
| * lock is contended. The lock will still be acquired but compaction will |
| * abort when the current block is finished regardless of success rate. |
| * Sync compaction acquires the lock. |
| * |
| * Always returns true which makes it easier to track lock state in callers. |
| */ |
| static bool compact_lock_irqsave(spinlock_t *lock, unsigned long *flags, |
| struct compact_control *cc) |
| __acquires(lock) |
| { |
| /* Track if the lock is contended in async mode */ |
| if (cc->mode == MIGRATE_ASYNC && !cc->contended) { |
| if (spin_trylock_irqsave(lock, *flags)) |
| return true; |
| |
| cc->contended = true; |
| } |
| |
| 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, 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. |
| * Returns false when compaction can continue. |
| */ |
| 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; |
| } |
| |
| 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, |
| unsigned int stride, |
| bool strict) |
| { |
| int nr_scanned = 0, total_isolated = 0; |
| struct page *page; |
| unsigned long flags = 0; |
| bool locked = false; |
| unsigned long blockpfn = *start_pfn; |
| unsigned int order; |
| |
| /* Strict mode is for isolation, speed is secondary */ |
| if (strict) |
| stride = 1; |
| |
| page = pfn_to_page(blockpfn); |
| |
| /* Isolate free pages. */ |
| for (; blockpfn < end_pfn; blockpfn += stride, page += stride) { |
| int isolated; |
| |
| /* |
| * Periodically drop the lock (if held) regardless of its |
| * contention, to give chance to IRQs. Abort if fatal signal |
| * pending. |
| */ |
| if (!(blockpfn % COMPACT_CLUSTER_MAX) |
| && compact_unlock_should_abort(&cc->zone->lock, flags, |
| &locked, cc)) |
| break; |
| |
| nr_scanned++; |
| |
| /* |
| * 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)) { |
| const unsigned int order = compound_order(page); |
| |
| if (blockpfn + (1UL << order) <= end_pfn) { |
| blockpfn += (1UL << order) - 1; |
| page += (1UL << order) - 1; |
| nr_scanned += (1UL << order) - 1; |
| } |
| |
| goto isolate_fail; |
| } |
| |
| if (!PageBuddy(page)) |
| goto isolate_fail; |
| |
| /* If we already hold the lock, we can skip some rechecking. */ |
| if (!locked) { |
| locked = compact_lock_irqsave(&cc->zone->lock, |
| &flags, cc); |
| |
| /* 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 = buddy_order(page); |
| isolated = __isolate_free_page(page, order); |
| if (!isolated) |
| break; |
| set_page_private(page, order); |
| |
| nr_scanned += isolated - 1; |
| total_isolated += isolated; |
| cc->nr_freepages += isolated; |
| list_add_tail(&page->lru, &freelist[order]); |
| |
| if (!strict && cc->nr_migratepages <= cc->nr_freepages) { |
| blockpfn += isolated; |
| break; |
| } |
| /* Advance to the end of split page */ |
| blockpfn += isolated - 1; |
| page += isolated - 1; |
| continue; |
| |
| isolate_fail: |
| if (strict) |
| break; |
| |
| } |
| |
| if (locked) |
| spin_unlock_irqrestore(&cc->zone->lock, flags); |
| |
| /* |
| * 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; |
| |
| cc->total_free_scanned += nr_scanned; |
| if (total_isolated) |
| count_compact_events(COMPACTISOLATED, total_isolated); |
| return total_isolated; |
| } |
| |
| /** |
| * isolate_freepages_range() - isolate free pages. |
| * @cc: Compaction control structure. |
| * @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; |
| int order; |
| struct list_head tmp_freepages[NR_PAGE_ORDERS]; |
| |
| for (order = 0; order < NR_PAGE_ORDERS; order++) |
| INIT_LIST_HEAD(&tmp_freepages[order]); |
| |
| 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; |
| |
| /* |
| * 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, tmp_freepages, 0, 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). |
| */ |
| } |
| |
| if (pfn < end_pfn) { |
| /* Loop terminated early, cleanup. */ |
| release_free_list(tmp_freepages); |
| return 0; |
| } |
| |
| /* __isolate_free_page() does not map the pages */ |
| split_map_pages(tmp_freepages); |
| |
| /* 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 compact_control *cc) |
| { |
| pg_data_t *pgdat = cc->zone->zone_pgdat; |
| bool too_many; |
| |
| unsigned long active, inactive, isolated; |
| |
| inactive = node_page_state(pgdat, NR_INACTIVE_FILE) + |
| node_page_state(pgdat, NR_INACTIVE_ANON); |
| active = node_page_state(pgdat, NR_ACTIVE_FILE) + |
| node_page_state(pgdat, NR_ACTIVE_ANON); |
| isolated = node_page_state(pgdat, NR_ISOLATED_FILE) + |
| node_page_state(pgdat, NR_ISOLATED_ANON); |
| |
| /* |
| * Allow GFP_NOFS to isolate past the limit set for regular |
| * compaction runs. This prevents an ABBA deadlock when other |
| * compactors have already isolated to the limit, but are |
| * blocked on filesystem locks held by the GFP_NOFS thread. |
| */ |
| if (cc->gfp_mask & __GFP_FS) { |
| inactive >>= 3; |
| active >>= 3; |
| } |
| |
| too_many = isolated > (inactive + active) / 2; |
| if (!too_many) |
| wake_throttle_isolated(pgdat); |
| |
| return too_many; |
| } |
| |
| /** |
| * skip_isolation_on_order() - determine when to skip folio isolation based on |
| * folio order and compaction target order |
| * @order: to-be-isolated folio order |
| * @target_order: compaction target order |
| * |
| * This avoids unnecessary folio isolations during compaction. |
| */ |
| static bool skip_isolation_on_order(int order, int target_order) |
| { |
| /* |
| * Unless we are performing global compaction (i.e., |
| * is_via_compact_memory), skip any folios that are larger than the |
| * target order: we wouldn't be here if we'd have a free folio with |
| * the desired target_order, so migrating this folio would likely fail |
| * later. |
| */ |
| if (!is_via_compact_memory(target_order) && order >= target_order) |
| return true; |
| /* |
| * We limit memory compaction to pageblocks and won't try |
| * creating free blocks of memory that are larger than that. |
| */ |
| return order >= pageblock_order; |
| } |
| |
| /** |
| * 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 |
| * @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 errno, like -EAGAIN or -EINTR in case e.g signal pending or congestion, |
| * -ENOMEM in case we could not allocate a page, or 0. |
| * cc->migrate_pfn will contain the next pfn to scan. |
| * |
| * The pages are isolated on cc->migratepages list (not required to be empty), |
| * and cc->nr_migratepages is updated accordingly. |
| */ |
| static int |
| isolate_migratepages_block(struct compact_control *cc, unsigned long low_pfn, |
| unsigned long end_pfn, isolate_mode_t mode) |
| { |
| pg_data_t *pgdat = cc->zone->zone_pgdat; |
| unsigned long nr_scanned = 0, nr_isolated = 0; |
| struct lruvec *lruvec; |
| unsigned long flags = 0; |
| struct lruvec *locked = NULL; |
| struct folio *folio = NULL; |
| struct page *page = NULL, *valid_page = NULL; |
| struct address_space *mapping; |
| unsigned long start_pfn = low_pfn; |
| bool skip_on_failure = false; |
| unsigned long next_skip_pfn = 0; |
| bool skip_updated = false; |
| int ret = 0; |
| |
| cc->migrate_pfn = low_pfn; |
| |
| /* |
| * 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(cc))) { |
| /* stop isolation if there are still pages not migrated */ |
| if (cc->nr_migratepages) |
| return -EAGAIN; |
| |
| /* async migration should just abort */ |
| if (cc->mode == MIGRATE_ASYNC) |
| return -EAGAIN; |
| |
| reclaim_throttle(pgdat, VMSCAN_THROTTLE_ISOLATED); |
| |
| if (fatal_signal_pending(current)) |
| return -EINTR; |
| } |
| |
| cond_resched(); |
| |
| 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++) { |
| bool is_dirty, is_unevictable; |
| |
| 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 completely if |
| * a fatal signal is pending. |
| */ |
| if (!(low_pfn % COMPACT_CLUSTER_MAX)) { |
| if (locked) { |
| unlock_page_lruvec_irqrestore(locked, flags); |
| locked = NULL; |
| } |
| |
| if (fatal_signal_pending(current)) { |
| cc->contended = true; |
| ret = -EINTR; |
| |
| goto fatal_pending; |
| } |
| |
| cond_resched(); |
| } |
| |
| nr_scanned++; |
| |
| page = pfn_to_page(low_pfn); |
| |
| /* |
| * Check if the pageblock has already been marked skipped. |
| * Only the first PFN is checked as the caller isolates |
| * COMPACT_CLUSTER_MAX at a time so the second call must |
| * not falsely conclude that the block should be skipped. |
| */ |
| if (!valid_page && (pageblock_aligned(low_pfn) || |
| low_pfn == cc->zone->zone_start_pfn)) { |
| if (!isolation_suitable(cc, page)) { |
| low_pfn = end_pfn; |
| folio = NULL; |
| goto isolate_abort; |
| } |
| valid_page = page; |
| } |
| |
| if (PageHuge(page)) { |
| /* |
| * skip hugetlbfs if we are not compacting for pages |
| * bigger than its order. THPs and other compound pages |
| * are handled below. |
| */ |
| if (!cc->alloc_contig) { |
| const unsigned int order = compound_order(page); |
| |
| if (order <= MAX_PAGE_ORDER) { |
| low_pfn += (1UL << order) - 1; |
| nr_scanned += (1UL << order) - 1; |
| } |
| goto isolate_fail; |
| } |
| /* for alloc_contig case */ |
| if (locked) { |
| unlock_page_lruvec_irqrestore(locked, flags); |
| locked = NULL; |
| } |
| |
| ret = isolate_or_dissolve_huge_page(page, &cc->migratepages); |
| |
| /* |
| * Fail isolation in case isolate_or_dissolve_huge_page() |
| * reports an error. In case of -ENOMEM, abort right away. |
| */ |
| if (ret < 0) { |
| /* Do not report -EBUSY down the chain */ |
| if (ret == -EBUSY) |
| ret = 0; |
| low_pfn += compound_nr(page) - 1; |
| nr_scanned += compound_nr(page) - 1; |
| goto isolate_fail; |
| } |
| |
| if (PageHuge(page)) { |
| /* |
| * Hugepage was successfully isolated and placed |
| * on the cc->migratepages list. |
| */ |
| folio = page_folio(page); |
| low_pfn += folio_nr_pages(folio) - 1; |
| goto isolate_success_no_list; |
| } |
| |
| /* |
| * Ok, the hugepage was dissolved. Now these pages are |
| * Buddy and cannot be re-allocated because they are |
| * isolated. Fall-through as the check below handles |
| * Buddy pages. |
| */ |
| } |
| |
| /* |
| * 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 = buddy_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_PAGE_ORDER) { |
| low_pfn += (1UL << freepage_order) - 1; |
| nr_scanned += (1UL << freepage_order) - 1; |
| } |
| continue; |
| } |
| |
| /* |
| * Regardless of being on LRU, compound pages such as THP |
| * (hugetlbfs is handled above) are not to be compacted unless |
| * we are attempting an allocation larger than the compound |
| * page size. 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) && !cc->alloc_contig) { |
| const unsigned int order = compound_order(page); |
| |
| /* Skip based on page order and compaction target order. */ |
| if (skip_isolation_on_order(order, cc->order)) { |
| if (order <= MAX_PAGE_ORDER) { |
| low_pfn += (1UL << order) - 1; |
| nr_scanned += (1UL << 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) { |
| unlock_page_lruvec_irqrestore(locked, flags); |
| locked = NULL; |
| } |
| |
| if (isolate_movable_page(page, mode)) { |
| folio = page_folio(page); |
| goto isolate_success; |
| } |
| } |
| |
| goto isolate_fail; |
| } |
| |
| /* |
| * Be careful not to clear PageLRU until after we're |
| * sure the page is not being freed elsewhere -- the |
| * page release code relies on it. |
| */ |
| folio = folio_get_nontail_page(page); |
| if (unlikely(!folio)) |
| 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. |
| */ |
| mapping = folio_mapping(folio); |
| if (!mapping && (folio_ref_count(folio) - 1) > folio_mapcount(folio)) |
| goto isolate_fail_put; |
| |
| /* |
| * Only allow to migrate anonymous pages in GFP_NOFS context |
| * because those do not depend on fs locks. |
| */ |
| if (!(cc->gfp_mask & __GFP_FS) && mapping) |
| goto isolate_fail_put; |
| |
| /* Only take pages on LRU: a check now makes later tests safe */ |
| if (!folio_test_lru(folio)) |
| goto isolate_fail_put; |
| |
| is_unevictable = folio_test_unevictable(folio); |
| |
| /* Compaction might skip unevictable pages but CMA takes them */ |
| if (!(mode & ISOLATE_UNEVICTABLE) && is_unevictable) |
| goto isolate_fail_put; |
| |
| /* |
| * To minimise LRU disruption, the caller can indicate with |
| * ISOLATE_ASYNC_MIGRATE that it only wants to isolate pages |
| * it will be able to migrate without blocking - clean pages |
| * for the most part. PageWriteback would require blocking. |
| */ |
| if ((mode & ISOLATE_ASYNC_MIGRATE) && folio_test_writeback(folio)) |
| goto isolate_fail_put; |
| |
| is_dirty = folio_test_dirty(folio); |
| |
| if (((mode & ISOLATE_ASYNC_MIGRATE) && is_dirty) || |
| (mapping && is_unevictable)) { |
| bool migrate_dirty = true; |
| bool is_inaccessible; |
| |
| /* |
| * Only folios without mappings or that have |
| * a ->migrate_folio callback are possible to migrate |
| * without blocking. |
| * |
| * Folios from inaccessible mappings are not migratable. |
| * |
| * However, we can be racing with truncation, which can |
| * free the mapping that we need to check. Truncation |
| * holds the folio lock until after the folio is removed |
| * from the page so holding it ourselves is sufficient. |
| * |
| * To avoid locking the folio just to check inaccessible, |
| * assume every inaccessible folio is also unevictable, |
| * which is a cheaper test. If our assumption goes |
| * wrong, it's not a correctness bug, just potentially |
| * wasted cycles. |
| */ |
| if (!folio_trylock(folio)) |
| goto isolate_fail_put; |
| |
| mapping = folio_mapping(folio); |
| if ((mode & ISOLATE_ASYNC_MIGRATE) && is_dirty) { |
| migrate_dirty = !mapping || |
| mapping->a_ops->migrate_folio; |
| } |
| is_inaccessible = mapping && mapping_inaccessible(mapping); |
| folio_unlock(folio); |
| if (!migrate_dirty || is_inaccessible) |
| goto isolate_fail_put; |
| } |
| |
| /* Try isolate the folio */ |
| if (!folio_test_clear_lru(folio)) |
| goto isolate_fail_put; |
| |
| lruvec = folio_lruvec(folio); |
| |
| /* If we already hold the lock, we can skip some rechecking */ |
| if (lruvec != locked) { |
| if (locked) |
| unlock_page_lruvec_irqrestore(locked, flags); |
| |
| compact_lock_irqsave(&lruvec->lru_lock, &flags, cc); |
| locked = lruvec; |
| |
| lruvec_memcg_debug(lruvec, folio); |
| |
| /* |
| * Try get exclusive access under lock. If marked for |
| * skip, the scan is aborted unless the current context |
| * is a rescan to reach the end of the pageblock. |
| */ |
| if (!skip_updated && valid_page) { |
| skip_updated = true; |
| if (test_and_set_skip(cc, valid_page) && |
| !cc->finish_pageblock) { |
| low_pfn = end_pfn; |
| goto isolate_abort; |
| } |
| } |
| |
| /* |
| * Check LRU folio order under the lock |
| */ |
| if (unlikely(skip_isolation_on_order(folio_order(folio), |
| cc->order) && |
| !cc->alloc_contig)) { |
| low_pfn += folio_nr_pages(folio) - 1; |
| nr_scanned += folio_nr_pages(folio) - 1; |
| folio_set_lru(folio); |
| goto isolate_fail_put; |
| } |
| } |
| |
| /* The folio is taken off the LRU */ |
| if (folio_test_large(folio)) |
| low_pfn += folio_nr_pages(folio) - 1; |
| |
| /* Successfully isolated */ |
| lruvec_del_folio(lruvec, folio); |
| node_stat_mod_folio(folio, |
| NR_ISOLATED_ANON + folio_is_file_lru(folio), |
| folio_nr_pages(folio)); |
| |
| isolate_success: |
| list_add(&folio->lru, &cc->migratepages); |
| isolate_success_no_list: |
| cc->nr_migratepages += folio_nr_pages(folio); |
| nr_isolated += folio_nr_pages(folio); |
| nr_scanned += folio_nr_pages(folio) - 1; |
| |
| /* |
| * Avoid isolating too much unless this block is being |
| * fully scanned (e.g. dirty/writeback pages, parallel allocation) |
| * or a lock is contended. For contention, isolate quickly to |
| * potentially remove one source of contention. |
| */ |
| if (cc->nr_migratepages >= COMPACT_CLUSTER_MAX && |
| !cc->finish_pageblock && !cc->contended) { |
| ++low_pfn; |
| break; |
| } |
| |
| continue; |
| |
| isolate_fail_put: |
| /* Avoid potential deadlock in freeing page under lru_lock */ |
| if (locked) { |
| unlock_page_lruvec_irqrestore(locked, flags); |
| locked = NULL; |
| } |
| folio_put(folio); |
| |
| isolate_fail: |
| if (!skip_on_failure && ret != -ENOMEM) |
| 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) { |
| unlock_page_lruvec_irqrestore(locked, flags); |
| locked = NULL; |
| } |
| putback_movable_pages(&cc->migratepages); |
| cc->nr_migratepages = 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; |
| } |
| |
| if (ret == -ENOMEM) |
| break; |
| } |
| |
| /* |
| * The PageBuddy() check could have potentially brought us outside |
| * the range to be scanned. |
| */ |
| if (unlikely(low_pfn > end_pfn)) |
| low_pfn = end_pfn; |
| |
| folio = NULL; |
| |
| isolate_abort: |
| if (locked) |
| unlock_page_lruvec_irqrestore(locked, flags); |
| if (folio) { |
| folio_set_lru(folio); |
| folio_put(folio); |
| } |
| |
| /* |
| * Update the cached scanner pfn once the pageblock has been scanned. |
| * Pages will either be migrated in which case there is no point |
| * scanning in the near future or migration failed in which case the |
| * failure reason may persist. The block is marked for skipping if |
| * there were no pages isolated in the block or if the block is |
| * rescanned twice in a row. |
| */ |
| if (low_pfn == end_pfn && (!nr_isolated || cc->finish_pageblock)) { |
| if (!cc->no_set_skip_hint && valid_page && !skip_updated) |
| set_pageblock_skip(valid_page); |
| update_cached_migrate(cc, low_pfn); |
| } |
| |
| trace_mm_compaction_isolate_migratepages(start_pfn, low_pfn, |
| nr_scanned, nr_isolated); |
| |
| fatal_pending: |
| cc->total_migrate_scanned += nr_scanned; |
| if (nr_isolated) |
| count_compact_events(COMPACTISOLATED, nr_isolated); |
| |
| cc->migrate_pfn = low_pfn; |
| |
| return ret; |
| } |
| |
| /** |
| * 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 -EAGAIN when contented, -EINTR in case of a signal pending, -ENOMEM |
| * in case we could not allocate a page, or 0. |
| */ |
| int |
| isolate_migratepages_range(struct compact_control *cc, unsigned long start_pfn, |
| unsigned long end_pfn) |
| { |
| unsigned long pfn, block_start_pfn, block_end_pfn; |
| int ret = 0; |
| |
| /* 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; |
| |
| ret = isolate_migratepages_block(cc, pfn, block_end_pfn, |
| ISOLATE_UNEVICTABLE); |
| |
| if (ret) |
| break; |
| |
| if (cc->nr_migratepages >= COMPACT_CLUSTER_MAX) |
| break; |
| } |
| |
| return ret; |
| } |
| |
| #endif /* CONFIG_COMPACTION || CONFIG_CMA */ |
| #ifdef CONFIG_COMPACTION |
| |
| static bool suitable_migration_source(struct compact_control *cc, |
| struct page *page) |
| { |
| int block_mt; |
| |
| if (pageblock_skip_persistent(page)) |
| return false; |
| |
| if ((cc->mode != MIGRATE_ASYNC) || !cc->direct_compaction) |
| return true; |
| |
| block_mt = get_pageblock_migratetype(page); |
| |
| if (cc->migratetype == MIGRATE_MOVABLE) |
| return is_migrate_movable(block_mt); |
| else |
| return block_mt == cc->migratetype; |
| } |
| |
| /* 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 the page is a large free page, then disallow migration */ |
| if (PageBuddy(page)) { |
| int order = cc->order > 0 ? cc->order : pageblock_order; |
| |
| /* |
| * 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 (buddy_order_unsafe(page) >= order) |
| return false; |
| } |
| |
| if (cc->ignore_block_suitable) |
| return true; |
| |
| /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */ |
| if (is_migrate_movable(get_pageblock_migratetype(page))) |
| return true; |
| |
| /* Otherwise skip the block */ |
| return false; |
| } |
| |
| static inline unsigned int |
| freelist_scan_limit(struct compact_control *cc) |
| { |
| unsigned short shift = BITS_PER_LONG - 1; |
| |
| return (COMPACT_CLUSTER_MAX >> min(shift, cc->fast_search_fail)) + 1; |
| } |
| |
| /* |
| * 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); |
| } |
| |
| /* |
| * Used when scanning for a suitable migration target which scans freelists |
| * in reverse. Reorders the list such as the unscanned pages are scanned |
| * first on the next iteration of the free scanner |
| */ |
| static void |
| move_freelist_head(struct list_head *freelist, struct page *freepage) |
| { |
| LIST_HEAD(sublist); |
| |
| if (!list_is_first(&freepage->buddy_list, freelist)) { |
| list_cut_before(&sublist, freelist, &freepage->buddy_list); |
| list_splice_tail(&sublist, freelist); |
| } |
| } |
| |
| /* |
| * Similar to move_freelist_head except used by the migration scanner |
| * when scanning forward. It's possible for these list operations to |
| * move against each other if they search the free list exactly in |
| * lockstep. |
| */ |
| static void |
| move_freelist_tail(struct list_head *freelist, struct page *freepage) |
| { |
| LIST_HEAD(sublist); |
| |
| if (!list_is_last(&freepage->buddy_list, freelist)) { |
| list_cut_position(&sublist, freelist, &freepage->buddy_list); |
| list_splice_tail(&sublist, freelist); |
| } |
| } |
| |
| static void |
| fast_isolate_around(struct compact_control *cc, unsigned long pfn) |
| { |
| unsigned long start_pfn, end_pfn; |
| struct page *page; |
| |
| /* Do not search around if there are enough pages already */ |
| if (cc->nr_freepages >= cc->nr_migratepages) |
| return; |
| |
| /* Minimise scanning during async compaction */ |
| if (cc->direct_compaction && cc->mode == MIGRATE_ASYNC) |
| return; |
| |
| /* Pageblock boundaries */ |
| start_pfn = max(pageblock_start_pfn(pfn), cc->zone->zone_start_pfn); |
| end_pfn = min(pageblock_end_pfn(pfn), zone_end_pfn(cc->zone)); |
| |
| page = pageblock_pfn_to_page(start_pfn, end_pfn, cc->zone); |
| if (!page) |
| return; |
| |
| isolate_freepages_block(cc, &start_pfn, end_pfn, cc->freepages, 1, false); |
| |
| /* Skip this pageblock in the future as it's full or nearly full */ |
| if (start_pfn == end_pfn && !cc->no_set_skip_hint) |
| set_pageblock_skip(page); |
| } |
| |
| /* Search orders in round-robin fashion */ |
| static int next_search_order(struct compact_control *cc, int order) |
| { |
| order--; |
| if (order < 0) |
| order = cc->order - 1; |
| |
| /* Search wrapped around? */ |
| if (order == cc->search_order) { |
| cc->search_order--; |
| if (cc->search_order < 0) |
| cc->search_order = cc->order - 1; |
| return -1; |
| } |
| |
| return order; |
| } |
| |
| static void fast_isolate_freepages(struct compact_control *cc) |
| { |
| unsigned int limit = max(1U, freelist_scan_limit(cc) >> 1); |
| unsigned int nr_scanned = 0, total_isolated = 0; |
| unsigned long low_pfn, min_pfn, highest = 0; |
| unsigned long nr_isolated = 0; |
| unsigned long distance; |
| struct page *page = NULL; |
| bool scan_start = false; |
| int order; |
| |
| /* Full compaction passes in a negative order */ |
| if (cc->order <= 0) |
| return; |
| |
| /* |
| * If starting the scan, use a deeper search and use the highest |
| * PFN found if a suitable one is not found. |
| */ |
| if (cc->free_pfn >= cc->zone->compact_init_free_pfn) { |
| limit = pageblock_nr_pages >> 1; |
| scan_start = true; |
| } |
| |
| /* |
| * Preferred point is in the top quarter of the scan space but take |
| * a pfn from the top half if the search is problematic. |
| */ |
| distance = (cc->free_pfn - cc->migrate_pfn); |
| low_pfn = pageblock_start_pfn(cc->free_pfn - (distance >> 2)); |
| min_pfn = pageblock_start_pfn(cc->free_pfn - (distance >> 1)); |
| |
| if (WARN_ON_ONCE(min_pfn > low_pfn)) |
| low_pfn = min_pfn; |
| |
| /* |
| * Search starts from the last successful isolation order or the next |
| * order to search after a previous failure |
| */ |
| cc->search_order = min_t(unsigned int, cc->order - 1, cc->search_order); |
| |
| for (order = cc->search_order; |
| !page && order >= 0; |
| order = next_search_order(cc, order)) { |
| struct free_area *area = &cc->zone->free_area[order]; |
| struct list_head *freelist; |
| struct page *freepage; |
| unsigned long flags; |
| unsigned int order_scanned = 0; |
| unsigned long high_pfn = 0; |
| |
| if (!area->nr_free) |
| continue; |
| |
| spin_lock_irqsave(&cc->zone->lock, flags); |
| freelist = &area->free_list[MIGRATE_MOVABLE]; |
| list_for_each_entry_reverse(freepage, freelist, buddy_list) { |
| unsigned long pfn; |
| |
| order_scanned++; |
| nr_scanned++; |
| pfn = page_to_pfn(freepage); |
| |
| if (pfn >= highest) |
| highest = max(pageblock_start_pfn(pfn), |
| cc->zone->zone_start_pfn); |
| |
| if (pfn >= low_pfn) { |
| cc->fast_search_fail = 0; |
| cc->search_order = order; |
| page = freepage; |
| break; |
| } |
| |
| if (pfn >= min_pfn && pfn > high_pfn) { |
| high_pfn = pfn; |
| |
| /* Shorten the scan if a candidate is found */ |
| limit >>= 1; |
| } |
| |
| if (order_scanned >= limit) |
| break; |
| } |
| |
| /* Use a maximum candidate pfn if a preferred one was not found */ |
| if (!page && high_pfn) { |
| page = pfn_to_page(high_pfn); |
| |
| /* Update freepage for the list reorder below */ |
| freepage = page; |
| } |
| |
| /* Reorder to so a future search skips recent pages */ |
| move_freelist_head(freelist, freepage); |
| |
| /* Isolate the page if available */ |
| if (page) { |
| if (__isolate_free_page(page, order)) { |
| set_page_private(page, order); |
| nr_isolated = 1 << order; |
| nr_scanned += nr_isolated - 1; |
| total_isolated += nr_isolated; |
| cc->nr_freepages += nr_isolated; |
| list_add_tail(&page->lru, &cc->freepages[order]); |
| count_compact_events(COMPACTISOLATED, nr_isolated); |
| } else { |
| /* If isolation fails, abort the search */ |
| order = cc->search_order + 1; |
| page = NULL; |
| } |
| } |
| |
| spin_unlock_irqrestore(&cc->zone->lock, flags); |
| |
| /* Skip fast search if enough freepages isolated */ |
| if (cc->nr_freepages >= cc->nr_migratepages) |
| break; |
| |
| /* |
| * Smaller scan on next order so the total scan is related |
| * to freelist_scan_limit. |
| */ |
| if (order_scanned >= limit) |
| limit = max(1U, limit >> 1); |
| } |
| |
| trace_mm_compaction_fast_isolate_freepages(min_pfn, cc->free_pfn, |
| nr_scanned, total_isolated); |
| |
| if (!page) { |
| cc->fast_search_fail++; |
| if (scan_start) { |
| /* |
| * Use the highest PFN found above min. If one was |
| * not found, be pessimistic for direct compaction |
| * and use the min mark. |
| */ |
| if (highest >= min_pfn) { |
| page = pfn_to_page(highest); |
| cc->free_pfn = highest; |
| } else { |
| if (cc->direct_compaction && pfn_valid(min_pfn)) { |
| page = pageblock_pfn_to_page(min_pfn, |
| min(pageblock_end_pfn(min_pfn), |
| zone_end_pfn(cc->zone)), |
| cc->zone); |
| if (page && !suitable_migration_target(cc, page)) |
| page = NULL; |
| |
| cc->free_pfn = min_pfn; |
| } |
| } |
| } |
| } |
| |
| if (highest && highest >= cc->zone->compact_cached_free_pfn) { |
| highest -= pageblock_nr_pages; |
| cc->zone->compact_cached_free_pfn = highest; |
| } |
| |
| cc->total_free_scanned += nr_scanned; |
| if (!page) |
| return; |
| |
| low_pfn = page_to_pfn(page); |
| fast_isolate_around(cc, low_pfn); |
| } |
| |
| /* |
| * 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 */ |
| unsigned int stride; |
| |
| /* Try a small search of the free lists for a candidate */ |
| fast_isolate_freepages(cc); |
| if (cc->nr_freepages) |
| return; |
| |
| /* |
| * 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 |
| * 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(isolate_start_pfn); |
| block_end_pfn = min(block_start_pfn + pageblock_nr_pages, |
| zone_end_pfn(zone)); |
| low_pfn = pageblock_end_pfn(cc->migrate_pfn); |
| stride = cc->mode == MIGRATE_ASYNC ? COMPACT_CLUSTER_MAX : 1; |
| |
| /* |
| * 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) { |
| unsigned long nr_isolated; |
| |
| /* |
| * This can iterate a massively long zone without finding any |
| * suitable migration targets, so periodically check resched. |
| */ |
| if (!(block_start_pfn % (COMPACT_CLUSTER_MAX * pageblock_nr_pages))) |
| cond_resched(); |
| |
| page = pageblock_pfn_to_page(block_start_pfn, block_end_pfn, |
| zone); |
| if (!page) { |
| unsigned long next_pfn; |
| |
| next_pfn = skip_offline_sections_reverse(block_start_pfn); |
| if (next_pfn) |
| block_start_pfn = max(next_pfn, low_pfn); |
| |
| 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. */ |
| nr_isolated = isolate_freepages_block(cc, &isolate_start_pfn, |
| block_end_pfn, cc->freepages, stride, false); |
| |
| /* Update the skip hint if the full pageblock was scanned */ |
| if (isolate_start_pfn == block_end_pfn) |
| update_pageblock_skip(cc, page, block_start_pfn - |
| pageblock_nr_pages); |
| |
| /* Are enough freepages isolated? */ |
| if (cc->nr_freepages >= cc->nr_migratepages) { |
| 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; |
| } |
| |
| /* Adjust stride depending on isolation */ |
| if (nr_isolated) { |
| stride = 1; |
| continue; |
| } |
| stride = min_t(unsigned int, COMPACT_CLUSTER_MAX, stride << 1); |
| } |
| |
| /* |
| * 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 folio *compaction_alloc_noprof(struct folio *src, unsigned long data) |
| { |
| struct compact_control *cc = (struct compact_control *)data; |
| struct folio *dst; |
| int order = folio_order(src); |
| bool has_isolated_pages = false; |
| int start_order; |
| struct page *freepage; |
| unsigned long size; |
| |
| again: |
| for (start_order = order; start_order < NR_PAGE_ORDERS; start_order++) |
| if (!list_empty(&cc->freepages[start_order])) |
| break; |
| |
| /* no free pages in the list */ |
| if (start_order == NR_PAGE_ORDERS) { |
| if (has_isolated_pages) |
| return NULL; |
| isolate_freepages(cc); |
| has_isolated_pages = true; |
| goto again; |
| } |
| |
| freepage = list_first_entry(&cc->freepages[start_order], struct page, |
| lru); |
| size = 1 << start_order; |
| |
| list_del(&freepage->lru); |
| |
| while (start_order > order) { |
| start_order--; |
| size >>= 1; |
| |
| list_add(&freepage[size].lru, &cc->freepages[start_order]); |
| set_page_private(&freepage[size], start_order); |
| } |
| dst = (struct folio *)freepage; |
| |
| post_alloc_hook(&dst->page, order, __GFP_MOVABLE); |
| if (order) |
| prep_compound_page(&dst->page, order); |
| cc->nr_freepages -= 1 << order; |
| cc->nr_migratepages -= 1 << order; |
| return page_rmappable_folio(&dst->page); |
| } |
| |
| static struct folio *compaction_alloc(struct folio *src, unsigned long data) |
| { |
| return alloc_hooks(compaction_alloc_noprof(src, data)); |
| } |
| |
| /* |
| * 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 folio *dst, unsigned long data) |
| { |
| struct compact_control *cc = (struct compact_control *)data; |
| int order = folio_order(dst); |
| struct page *page = &dst->page; |
| |
| if (folio_put_testzero(dst)) { |
| free_pages_prepare(page, order); |
| list_add(&dst->lru, &cc->freepages[order]); |
| cc->nr_freepages += 1 << order; |
| } |
| cc->nr_migratepages += 1 << order; |
| /* |
| * someone else has referenced the page, we cannot take it back to our |
| * free list. |
| */ |
| } |
| |
| /* 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. |
| */ |
| static int sysctl_compact_unevictable_allowed __read_mostly = CONFIG_COMPACT_UNEVICTABLE_DEFAULT; |
| /* |
| * Tunable for proactive compaction. It determines how |
| * aggressively the kernel should compact memory in the |
| * background. It takes values in the range [0, 100]. |
| */ |
| static unsigned int __read_mostly sysctl_compaction_proactiveness = 20; |
| static int sysctl_extfrag_threshold = 500; |
| static int __read_mostly sysctl_compact_memory; |
| |
| static inline void |
| update_fast_start_pfn(struct compact_control *cc, unsigned long pfn) |
| { |
| if (cc->fast_start_pfn == ULONG_MAX) |
| return; |
| |
| if (!cc->fast_start_pfn) |
| cc->fast_start_pfn = pfn; |
| |
| cc->fast_start_pfn = min(cc->fast_start_pfn, pfn); |
| } |
| |
| static inline unsigned long |
| reinit_migrate_pfn(struct compact_control *cc) |
| { |
| if (!cc->fast_start_pfn || cc->fast_start_pfn == ULONG_MAX) |
| return cc->migrate_pfn; |
| |
| cc->migrate_pfn = cc->fast_start_pfn; |
| cc->fast_start_pfn = ULONG_MAX; |
| |
| return cc->migrate_pfn; |
| } |
| |
| /* |
| * Briefly search the free lists for a migration source that already has |
| * some free pages to reduce the number of pages that need migration |
| * before a pageblock is free. |
| */ |
| static unsigned long fast_find_migrateblock(struct compact_control *cc) |
| { |
| unsigned int limit = freelist_scan_limit(cc); |
| unsigned int nr_scanned = 0; |
| unsigned long distance; |
| unsigned long pfn = cc->migrate_pfn; |
| unsigned long high_pfn; |
| int order; |
| bool found_block = false; |
| |
| /* Skip hints are relied on to avoid repeats on the fast search */ |
| if (cc->ignore_skip_hint) |
| return pfn; |
| |
| /* |
| * If the pageblock should be finished then do not select a different |
| * pageblock. |
| */ |
| if (cc->finish_pageblock) |
| return pfn; |
| |
| /* |
| * If the migrate_pfn is not at the start of a zone or the start |
| * of a pageblock then assume this is a continuation of a previous |
| * scan restarted due to COMPACT_CLUSTER_MAX. |
| */ |
| if (pfn != cc->zone->zone_start_pfn && pfn != pageblock_start_pfn(pfn)) |
| return pfn; |
| |
| /* |
| * For smaller orders, just linearly scan as the number of pages |
| * to migrate should be relatively small and does not necessarily |
| * justify freeing up a large block for a small allocation. |
| */ |
| if (cc->order <= PAGE_ALLOC_COSTLY_ORDER) |
| return pfn; |
| |
| /* |
| * Only allow kcompactd and direct requests for movable pages to |
| * quickly clear out a MOVABLE pageblock for allocation. This |
| * reduces the risk that a large movable pageblock is freed for |
| * an unmovable/reclaimable small allocation. |
| */ |
| if (cc->direct_compaction && cc->migratetype != MIGRATE_MOVABLE) |
| return pfn; |
| |
| /* |
| * When starting the migration scanner, pick any pageblock within the |
| * first half of the search space. Otherwise try and pick a pageblock |
| * within the first eighth to reduce the chances that a migration |
| * target later becomes a source. |
| */ |
| distance = (cc->free_pfn - cc->migrate_pfn) >> 1; |
| if (cc->migrate_pfn != cc->zone->zone_start_pfn) |
| distance >>= 2; |
| high_pfn = pageblock_start_pfn(cc->migrate_pfn + distance); |
| |
| for (order = cc->order - 1; |
| order >= PAGE_ALLOC_COSTLY_ORDER && !found_block && nr_scanned < limit; |
| order--) { |
| struct free_area *area = &cc->zone->free_area[order]; |
| struct list_head *freelist; |
| unsigned long flags; |
| struct page *freepage; |
| |
| if (!area->nr_free) |
| continue; |
| |
| spin_lock_irqsave(&cc->zone->lock, flags); |
| freelist = &area->free_list[MIGRATE_MOVABLE]; |
| list_for_each_entry(freepage, freelist, buddy_list) { |
| unsigned long free_pfn; |
| |
| if (nr_scanned++ >= limit) { |
| move_freelist_tail(freelist, freepage); |
| break; |
| } |
| |
| free_pfn = page_to_pfn(freepage); |
| if (free_pfn < high_pfn) { |
| /* |
| * Avoid if skipped recently. Ideally it would |
| * move to the tail but even safe iteration of |
| * the list assumes an entry is deleted, not |
| * reordered. |
| */ |
| if (get_pageblock_skip(freepage)) |
| continue; |
| |
| /* Reorder to so a future search skips recent pages */ |
| move_freelist_tail(freelist, freepage); |
| |
| update_fast_start_pfn(cc, free_pfn); |
| pfn = pageblock_start_pfn(free_pfn); |
| if (pfn < cc->zone->zone_start_pfn) |
| pfn = cc->zone->zone_start_pfn; |
| cc->fast_search_fail = 0; |
| found_block = true; |
| break; |
| } |
| } |
| spin_unlock_irqrestore(&cc->zone->lock, flags); |
| } |
| |
| cc->total_migrate_scanned += nr_scanned; |
| |
| /* |
| * If fast scanning failed then use a cached entry for a page block |
| * that had free pages as the basis for starting a linear scan. |
| */ |
| if (!found_block) { |
| cc->fast_search_fail++; |
| pfn = reinit_migrate_pfn(cc); |
| } |
| return pfn; |
| } |
| |
| /* |
| * 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 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); |
| bool fast_find_block; |
| |
| /* |
| * Start at where we last stopped, or beginning of the zone as |
| * initialized by compact_zone(). The first failure will use |
| * the lowest PFN as the starting point for linear scanning. |
| */ |
| low_pfn = fast_find_migrateblock(cc); |
| block_start_pfn = pageblock_start_pfn(low_pfn); |
| if (block_start_pfn < cc->zone->zone_start_pfn) |
| block_start_pfn = cc->zone->zone_start_pfn; |
| |
| /* |
| * fast_find_migrateblock() has already ensured the pageblock is not |
| * set with a skipped flag, so to avoid the isolation_suitable check |
| * below again, check whether the fast search was successful. |
| */ |
| fast_find_block = low_pfn != cc->migrate_pfn && !cc->fast_search_fail; |
| |
| /* 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; |
| fast_find_block = false, |
| cc->migrate_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. |
| */ |
| if (!(low_pfn % (COMPACT_CLUSTER_MAX * pageblock_nr_pages))) |
| cond_resched(); |
| |
| page = pageblock_pfn_to_page(block_start_pfn, |
| block_end_pfn, cc->zone); |
| if (!page) { |
| unsigned long next_pfn; |
| |
| next_pfn = skip_offline_sections(block_start_pfn); |
| if (next_pfn) |
| block_end_pfn = min(next_pfn, cc->free_pfn); |
| continue; |
| } |
| |
| /* |
| * If isolation recently failed, do not retry. Only check the |
| * pageblock once. COMPACT_CLUSTER_MAX causes a pageblock |
| * to be visited multiple times. Assume skip was checked |
| * before making it "skip" so other compaction instances do |
| * not scan the same block. |
| */ |
| if ((pageblock_aligned(low_pfn) || |
| low_pfn == cc->zone->zone_start_pfn) && |
| !fast_find_block && !isolation_suitable(cc, page)) |
| continue; |
| |
| /* |
| * For async direct compaction, only scan the pageblocks of the |
| * same migratetype without huge pages. Async direct compaction |
| * is optimistic to see if the minimum amount of work satisfies |
| * the allocation. The cached PFN is updated as it's possible |
| * that all remaining blocks between source and target are |
| * unsuitable and the compaction scanners fail to meet. |
| */ |
| if (!suitable_migration_source(cc, page)) { |
| update_cached_migrate(cc, block_end_pfn); |
| continue; |
| } |
| |
| /* Perform the isolation */ |
| if (isolate_migratepages_block(cc, low_pfn, block_end_pfn, |
| isolate_mode)) |
| 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; |
| } |
| |
| return cc->nr_migratepages ? ISOLATE_SUCCESS : ISOLATE_NONE; |
| } |
| |
| /* |
| * Determine whether kswapd is (or recently was!) running on this node. |
| * |
| * pgdat_kswapd_lock() pins pgdat->kswapd, so a concurrent kswapd_stop() can't |
| * zero it. |
| */ |
| static bool kswapd_is_running(pg_data_t *pgdat) |
| { |
| bool running; |
| |
| pgdat_kswapd_lock(pgdat); |
| running = pgdat->kswapd && task_is_running(pgdat->kswapd); |
| pgdat_kswapd_unlock(pgdat); |
| |
| return running; |
| } |
| |
| /* |
| * A zone's fragmentation score is the external fragmentation wrt to the |
| * COMPACTION_HPAGE_ORDER. It returns a value in the range [0, 100]. |
| */ |
| static unsigned int fragmentation_score_zone(struct zone *zone) |
| { |
| return extfrag_for_order(zone, COMPACTION_HPAGE_ORDER); |
| } |
| |
| /* |
| * A weighted zone's fragmentation score is the external fragmentation |
| * wrt to the COMPACTION_HPAGE_ORDER scaled by the zone's size. It |
| * returns a value in the range [0, 100]. |
| * |
| * The scaling factor ensures that proactive compaction focuses on larger |
| * zones like ZONE_NORMAL, rather than smaller, specialized zones like |
| * ZONE_DMA32. For smaller zones, the score value remains close to zero, |
| * and thus never exceeds the high threshold for proactive compaction. |
| */ |
| static unsigned int fragmentation_score_zone_weighted(struct zone *zone) |
| { |
| unsigned long score; |
| |
| score = zone->present_pages * fragmentation_score_zone(zone); |
| return div64_ul(score, zone->zone_pgdat->node_present_pages + 1); |
| } |
| |
| /* |
| * The per-node proactive (background) compaction process is started by its |
| * corresponding kcompactd thread when the node's fragmentation score |
| * exceeds the high threshold. The compaction process remains active till |
| * the node's score falls below the low threshold, or one of the back-off |
| * conditions is met. |
| */ |
| static unsigned int fragmentation_score_node(pg_data_t *pgdat) |
| { |
| unsigned int score = 0; |
| int zoneid; |
| |
| for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { |
| struct zone *zone; |
| |
| zone = &pgdat->node_zones[zoneid]; |
| if (!populated_zone(zone)) |
| continue; |
| score += fragmentation_score_zone_weighted(zone); |
| } |
| |
| return score; |
| } |
| |
| static unsigned int fragmentation_score_wmark(bool low) |
| { |
| unsigned int wmark_low; |
| |
| /* |
| * Cap the low watermark to avoid excessive compaction |
| * activity in case a user sets the proactiveness tunable |
| * close to 100 (maximum). |
| */ |
| wmark_low = max(100U - sysctl_compaction_proactiveness, 5U); |
| return low ? wmark_low : min(wmark_low + 10, 100U); |
| } |
| |
| static bool should_proactive_compact_node(pg_data_t *pgdat) |
| { |
| int wmark_high; |
| |
| if (!sysctl_compaction_proactiveness || kswapd_is_running(pgdat)) |
| return false; |
| |
| wmark_high = fragmentation_score_wmark(false); |
| return fragmentation_score_node(pgdat) > wmark_high; |
| } |
| |
| static enum compact_result __compact_finished(struct compact_control *cc) |
| { |
| unsigned int order; |
| const int migratetype = cc->migratetype; |
| int ret; |
| |
| /* Compaction run completes if the migrate and free scanner meet */ |
| if (compact_scanners_met(cc)) { |
| /* Let the next compaction start anew. */ |
| reset_cached_positions(cc->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) |
| cc->zone->compact_blockskip_flush = true; |
| |
| if (cc->whole_zone) |
| return COMPACT_COMPLETE; |
| else |
| return COMPACT_PARTIAL_SKIPPED; |
| } |
| |
| if (cc->proactive_compaction) { |
| int score, wmark_low; |
| pg_data_t *pgdat; |
| |
| pgdat = cc->zone->zone_pgdat; |
| if (kswapd_is_running(pgdat)) |
| return COMPACT_PARTIAL_SKIPPED; |
| |
| score = fragmentation_score_zone(cc->zone); |
| wmark_low = fragmentation_score_wmark(true); |
| |
| if (score > wmark_low) |
| ret = COMPACT_CONTINUE; |
| else |
| ret = COMPACT_SUCCESS; |
| |
| goto out; |
| } |
| |
| if (is_via_compact_memory(cc->order)) |
| return COMPACT_CONTINUE; |
| |
| /* |
| * Always finish scanning a pageblock to reduce the possibility of |
| * fallbacks in the future. This is particularly important when |
| * migration source is unmovable/reclaimable but it's not worth |
| * special casing. |
| */ |
| if (!pageblock_aligned(cc->migrate_pfn)) |
| return COMPACT_CONTINUE; |
| |
| /* Direct compactor: Is a suitable page free? */ |
| ret = COMPACT_NO_SUITABLE_PAGE; |
| for (order = cc->order; order < NR_PAGE_ORDERS; order++) { |
| struct free_area *area = &cc->zone->free_area[order]; |
| bool can_steal; |
| |
| /* Job done if page is free of the right migratetype */ |
| if (!free_area_empty(area, migratetype)) |
| return COMPACT_SUCCESS; |
| |
| #ifdef CONFIG_CMA |
| /* MIGRATE_MOVABLE can fallback on MIGRATE_CMA */ |
| if (migratetype == MIGRATE_MOVABLE && |
| !free_area_empty(area, 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) |
| /* |
| * Movable pages are OK in any pageblock. If we are |
| * stealing for a non-movable allocation, make sure |
| * we finish compacting the current pageblock first |
| * (which is assured by the above migrate_pfn align |
| * check) so it is as free as possible and we won't |
| * have to steal another one soon. |
| */ |
| return COMPACT_SUCCESS; |
| } |
| |
| out: |
| if (cc->contended || fatal_signal_pending(current)) |
| ret = COMPACT_CONTENDED; |
| |
| return ret; |
| } |
| |
| static enum compact_result compact_finished(struct compact_control *cc) |
| { |
| int ret; |
| |
| ret = __compact_finished(cc); |
| trace_mm_compaction_finished(cc->zone, cc->order, ret); |
| if (ret == COMPACT_NO_SUITABLE_PAGE) |
| ret = COMPACT_CONTINUE; |
| |
| return ret; |
| } |
| |
| static bool __compaction_suitable(struct zone *zone, int order, |
| int highest_zoneidx, |
| unsigned long wmark_target) |
| { |
| unsigned long watermark; |
| /* |
| * 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 highest_zoneidx |
| * 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); |
| return __zone_watermark_ok(zone, 0, watermark, highest_zoneidx, |
| ALLOC_CMA, wmark_target); |
| } |
| |
| /* |
| * compaction_suitable: Is this suitable to run compaction on this zone now? |
| */ |
| bool compaction_suitable(struct zone *zone, int order, int highest_zoneidx) |
| { |
| enum compact_result compact_result; |
| bool suitable; |
| |
| suitable = __compaction_suitable(zone, order, highest_zoneidx, |
| 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 (suitable) { |
| compact_result = COMPACT_CONTINUE; |
| if (order > PAGE_ALLOC_COSTLY_ORDER) { |
| int fragindex = fragmentation_index(zone, order); |
| |
| if (fragindex >= 0 && |
| fragindex <= sysctl_extfrag_threshold) { |
| suitable = false; |
| compact_result = COMPACT_NOT_SUITABLE_ZONE; |
| } |
| } |
| } else { |
| compact_result = COMPACT_SKIPPED; |
| } |
| |
| trace_mm_compaction_suitable(zone, order, compact_result); |
| |
| return suitable; |
| } |
| |
| 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->highest_zoneidx, ac->nodemask) { |
| unsigned long available; |
| |
| /* |
| * 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); |
| if (__compaction_suitable(zone, order, ac->highest_zoneidx, |
| available)) |
| return true; |
| } |
| |
| return false; |
| } |
| |
| /* |
| * Should we do compaction for target allocation order. |
| * Return COMPACT_SUCCESS if allocation for target order can be already |
| * satisfied |
| * Return COMPACT_SKIPPED if compaction for target order is likely to fail |
| * Return COMPACT_CONTINUE if compaction for target order should be ran |
| */ |
| static enum compact_result |
| compaction_suit_allocation_order(struct zone *zone, unsigned int order, |
| int highest_zoneidx, unsigned int alloc_flags) |
| { |
| unsigned long watermark; |
| |
| watermark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK); |
| if (zone_watermark_ok(zone, order, watermark, highest_zoneidx, |
| alloc_flags)) |
| return COMPACT_SUCCESS; |
| |
| if (!compaction_suitable(zone, order, highest_zoneidx)) |
| return COMPACT_SKIPPED; |
| |
| return COMPACT_CONTINUE; |
| } |
| |
| static enum compact_result |
| compact_zone(struct compact_control *cc, struct capture_control *capc) |
| { |
| enum compact_result ret; |
| unsigned long start_pfn = cc->zone->zone_start_pfn; |
| unsigned long end_pfn = zone_end_pfn(cc->zone); |
| unsigned long last_migrated_pfn; |
| const bool sync = cc->mode != MIGRATE_ASYNC; |
| bool update_cached; |
| unsigned int nr_succeeded = 0, nr_migratepages; |
| int order; |
| |
| /* |
| * These counters track activities during zone compaction. Initialize |
| * them before compacting a new zone. |
| */ |
| cc->total_migrate_scanned = 0; |
| cc->total_free_scanned = 0; |
| cc->nr_migratepages = 0; |
| cc->nr_freepages = 0; |
| for (order = 0; order < NR_PAGE_ORDERS; order++) |
| INIT_LIST_HEAD(&cc->freepages[order]); |
| INIT_LIST_HEAD(&cc->migratepages); |
| |
| cc->migratetype = gfp_migratetype(cc->gfp_mask); |
| |
| if (!is_via_compact_memory(cc->order)) { |
| ret = compaction_suit_allocation_order(cc->zone, cc->order, |
| cc->highest_zoneidx, |
| cc->alloc_flags); |
| if (ret != COMPACT_CONTINUE) |
| return ret; |
| } |
| |
| /* |
| * Clear pageblock skip if there were failures recently and compaction |
| * is about to be retried after being deferred. |
| */ |
| if (compaction_restarting(cc->zone, cc->order)) |
| __reset_isolation_suitable(cc->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. |
| */ |
| cc->fast_start_pfn = 0; |
| if (cc->whole_zone) { |
| cc->migrate_pfn = start_pfn; |
| cc->free_pfn = pageblock_start_pfn(end_pfn - 1); |
| } else { |
| cc->migrate_pfn = cc->zone->compact_cached_migrate_pfn[sync]; |
| cc->free_pfn = cc->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); |
| cc->zone->compact_cached_free_pfn = cc->free_pfn; |
| } |
| if (cc->migrate_pfn < start_pfn || cc->migrate_pfn >= end_pfn) { |
| cc->migrate_pfn = start_pfn; |
| cc->zone->compact_cached_migrate_pfn[0] = cc->migrate_pfn; |
| cc->zone->compact_cached_migrate_pfn[1] = cc->migrate_pfn; |
| } |
| |
| if (cc->migrate_pfn <= cc->zone->compact_init_migrate_pfn) |
| cc->whole_zone = true; |
| } |
| |
| last_migrated_pfn = 0; |
| |
| /* |
| * Migrate has separate cached PFNs for ASYNC and SYNC* migration on |
| * the basis that some migrations will fail in ASYNC mode. However, |
| * if the cached PFNs match and pageblocks are skipped due to having |
| * no isolation candidates, then the sync state does not matter. |
| * Until a pageblock with isolation candidates is found, keep the |
| * cached PFNs in sync to avoid revisiting the same blocks. |
| */ |
| update_cached = !sync && |
| cc->zone->compact_cached_migrate_pfn[0] == cc->zone->compact_cached_migrate_pfn[1]; |
| |
| trace_mm_compaction_begin(cc, start_pfn, end_pfn, sync); |
| |
| /* lru_add_drain_all could be expensive with involving other CPUs */ |
| lru_add_drain(); |
| |
| while ((ret = compact_finished(cc)) == COMPACT_CONTINUE) { |
| int err; |
| unsigned long iteration_start_pfn = cc->migrate_pfn; |
| |
| /* |
| * Avoid multiple rescans of the same pageblock which can |
| * happen if a page cannot be isolated (dirty/writeback in |
| * async mode) or if the migrated pages are being allocated |
| * before the pageblock is cleared. The first rescan will |
| * capture the entire pageblock for migration. If it fails, |
| * it'll be marked skip and scanning will proceed as normal. |
| */ |
| cc->finish_pageblock = false; |
| if (pageblock_start_pfn(last_migrated_pfn) == |
| pageblock_start_pfn(iteration_start_pfn)) { |
| cc->finish_pageblock = true; |
| } |
| |
| rescan: |
| switch (isolate_migratepages(cc)) { |
| case ISOLATE_ABORT: |
| ret = COMPACT_CONTENDED; |
| putback_movable_pages(&cc->migratepages); |
| cc->nr_migratepages = 0; |
| goto out; |
| case ISOLATE_NONE: |
| if (update_cached) { |
| cc->zone->compact_cached_migrate_pfn[1] = |
| cc->zone->compact_cached_migrate_pfn[0]; |
| } |
| |
| /* |
| * 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: |
| update_cached = false; |
| last_migrated_pfn = max(cc->zone->zone_start_pfn, |
| pageblock_start_pfn(cc->migrate_pfn - 1)); |
| } |
| |
| /* |
| * Record the number of pages to migrate since the |
| * compaction_alloc/free() will update cc->nr_migratepages |
| * properly. |
| */ |
| nr_migratepages = cc->nr_migratepages; |
| err = migrate_pages(&cc->migratepages, compaction_alloc, |
| compaction_free, (unsigned long)cc, cc->mode, |
| MR_COMPACTION, &nr_succeeded); |
| |
| trace_mm_compaction_migratepages(nr_migratepages, nr_succeeded); |
| |
| /* 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; |
| } |
| /* |
| * If an ASYNC or SYNC_LIGHT fails to migrate a page |
| * within the pageblock_order-aligned block and |
| * fast_find_migrateblock may be used then scan the |
| * remainder of the pageblock. This will mark the |
| * pageblock "skip" to avoid rescanning in the near |
| * future. This will isolate more pages than necessary |
| * for the request but avoid loops due to |
| * fast_find_migrateblock revisiting blocks that were |
| * recently partially scanned. |
| */ |
| if (!pageblock_aligned(cc->migrate_pfn) && |
| !cc->ignore_skip_hint && !cc->finish_pageblock && |
| (cc->mode < MIGRATE_SYNC)) { |
| cc->finish_pageblock = true; |
| |
| /* |
| * Draining pcplists does not help THP if |
| * any page failed to migrate. Even after |
| * drain, the pageblock will not be free. |
| */ |
| if (cc->order == COMPACTION_HPAGE_ORDER) |
| last_migrated_pfn = 0; |
| |
| goto rescan; |
| } |
| } |
| |
| /* Stop if a page has been captured */ |
| if (capc && capc->page) { |
| ret = COMPACT_SUCCESS; |
| break; |
| } |
| |
| 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 && last_migrated_pfn) { |
| unsigned long current_block_start = |
| block_start_pfn(cc->migrate_pfn, cc->order); |
| |
| if (last_migrated_pfn < current_block_start) { |
| lru_add_drain_cpu_zone(cc->zone); |
| /* No more flushing until we migrate again */ |
| 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_free_list(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 > cc->zone->compact_cached_free_pfn) |
| cc->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(cc, start_pfn, end_pfn, sync, ret); |
| |
| VM_BUG_ON(!list_empty(&cc->migratepages)); |
| |
| 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 highest_zoneidx, |
| struct page **capture) |
| { |
| enum compact_result ret; |
| struct compact_control cc = { |
| .order = order, |
| .search_order = order, |
| .gfp_mask = gfp_mask, |
| .zone = zone, |
| .mode = (prio == COMPACT_PRIO_ASYNC) ? |
| MIGRATE_ASYNC : MIGRATE_SYNC_LIGHT, |
| .alloc_flags = alloc_flags, |
| .highest_zoneidx = highest_zoneidx, |
| .direct_compaction = true, |
| .whole_zone = (prio == MIN_COMPACT_PRIORITY), |
| .ignore_skip_hint = (prio == MIN_COMPACT_PRIORITY), |
| .ignore_block_suitable = (prio == MIN_COMPACT_PRIORITY) |
| }; |
| struct capture_control capc = { |
| .cc = &cc, |
| .page = NULL, |
| }; |
| |
| /* |
| * Make sure the structs are really initialized before we expose the |
| * capture control, in case we are interrupted and the interrupt handler |
| * frees a page. |
| */ |
| barrier(); |
| WRITE_ONCE(current->capture_control, &capc); |
| |
| ret = compact_zone(&cc, &capc); |
| |
| /* |
| * Make sure we hide capture control first before we read the captured |
| * page pointer, otherwise an interrupt could free and capture a page |
| * and we would leak it. |
| */ |
| WRITE_ONCE(current->capture_control, NULL); |
| *capture = READ_ONCE(capc.page); |
| /* |
| * Technically, it is also possible that compaction is skipped but |
| * the page is still captured out of luck(IRQ came and freed the page). |
| * Returning COMPACT_SUCCESS in such cases helps in properly accounting |
| * the COMPACT[STALL|FAIL] when compaction is skipped. |
| */ |
| if (*capture) |
| ret = COMPACT_SUCCESS; |
| |
| return ret; |
| } |
| |
| /** |
| * 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 |
| * @prio: Determines how hard direct compaction should try to succeed |
| * @capture: Pointer to free page created by compaction will be stored here |
| * |
| * 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, struct page **capture) |
| { |
| struct zoneref *z; |
| struct zone *zone; |
| enum compact_result rc = COMPACT_SKIPPED; |
| |
| if (!gfp_compaction_allowed(gfp_mask)) |
| 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->highest_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->highest_zoneidx, capture); |
| 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_node() - compact all zones within a node |
| * @pgdat: The node page data |
| * @proactive: Whether the compaction is proactive |
| * |
| * For proactive compaction, compact till each zone's fragmentation score |
| * reaches within proactive compaction thresholds (as determined by the |
| * proactiveness tunable), it is possible that the function returns before |
| * reaching score targets due to various back-off conditions, such as, |
| * contention on per-node or per-zone locks. |
| */ |
| static int compact_node(pg_data_t *pgdat, bool proactive) |
| { |
| int zoneid; |
| struct zone *zone; |
| struct compact_control cc = { |
| .order = -1, |
| .mode = proactive ? MIGRATE_SYNC_LIGHT : MIGRATE_SYNC, |
| .ignore_skip_hint = true, |
| .whole_zone = true, |
| .gfp_mask = GFP_KERNEL, |
| .proactive_compaction = proactive, |
| }; |
| |
| for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { |
| zone = &pgdat->node_zones[zoneid]; |
| if (!populated_zone(zone)) |
| continue; |
| |
| if (fatal_signal_pending(current)) |
| return -EINTR; |
| |
| cc.zone = zone; |
| |
| compact_zone(&cc, NULL); |
| |
| if (proactive) { |
| count_compact_events(KCOMPACTD_MIGRATE_SCANNED, |
| cc.total_migrate_scanned); |
| count_compact_events(KCOMPACTD_FREE_SCANNED, |
| cc.total_free_scanned); |
| } |
| } |
| |
| return 0; |
| } |
| |
| /* Compact all zones of all nodes in the system */ |
| static int compact_nodes(void) |
| { |
| int ret, nid; |
| |
| /* Flush pending updates to the LRU lists */ |
| lru_add_drain_all(); |
| |
| for_each_online_node(nid) { |
| ret = compact_node(NODE_DATA(nid), false); |
| if (ret) |
| return ret; |
| } |
| |
| return 0; |
| } |
| |
| static int compaction_proactiveness_sysctl_handler(const struct ctl_table *table, int write, |
| void *buffer, size_t *length, loff_t *ppos) |
| { |
| int rc, nid; |
| |
| rc = proc_dointvec_minmax(table, write, buffer, length, ppos); |
| if (rc) |
| return rc; |
| |
| if (write && sysctl_compaction_proactiveness) { |
| for_each_online_node(nid) { |
| pg_data_t *pgdat = NODE_DATA(nid); |
| |
| if (pgdat->proactive_compact_trigger) |
| continue; |
| |
| pgdat->proactive_compact_trigger = true; |
| trace_mm_compaction_wakeup_kcompactd(pgdat->node_id, -1, |
| pgdat->nr_zones - 1); |
| wake_up_interruptible(&pgdat->kcompactd_wait); |
| } |
| } |
| |
| return 0; |
| } |
| |
| /* |
| * This is the entry point for compacting all nodes via |
| * /proc/sys/vm/compact_memory |
| */ |
| static int sysctl_compaction_handler(const struct ctl_table *table, int write, |
| void *buffer, size_t *length, loff_t *ppos) |
| { |
| int ret; |
| |
| ret = proc_dointvec(table, write, buffer, length, ppos); |
| if (ret) |
| return ret; |
| |
| if (sysctl_compact_memory != 1) |
| return -EINVAL; |
| |
| if (write) |
| ret = compact_nodes(); |
| |
| return ret; |
| } |
| |
| #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA) |
| static ssize_t compact_store(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(NODE_DATA(nid), false); |
| } |
| |
| return count; |
| } |
| static DEVICE_ATTR_WO(compact); |
| |
| int compaction_register_node(struct node *node) |
| { |
| return device_create_file(&node->dev, &dev_attr_compact); |
| } |
| |
| void compaction_unregister_node(struct node *node) |
| { |
| 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() || |
| pgdat->proactive_compact_trigger; |
| } |
| |
| static bool kcompactd_node_suitable(pg_data_t *pgdat) |
| { |
| int zoneid; |
| struct zone *zone; |
| enum zone_type highest_zoneidx = pgdat->kcompactd_highest_zoneidx; |
| enum compact_result ret; |
| |
| for (zoneid = 0; zoneid <= highest_zoneidx; zoneid++) { |
| zone = &pgdat->node_zones[zoneid]; |
| |
| if (!populated_zone(zone)) |
| continue; |
| |
| ret = compaction_suit_allocation_order(zone, |
| pgdat->kcompactd_max_order, |
| highest_zoneidx, ALLOC_WMARK_MIN); |
| if (ret == 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, |
| .search_order = pgdat->kcompactd_max_order, |
| .highest_zoneidx = pgdat->kcompactd_highest_zoneidx, |
| .mode = MIGRATE_SYNC_LIGHT, |
| .ignore_skip_hint = false, |
| .gfp_mask = GFP_KERNEL, |
| }; |
| enum compact_result ret; |
| |
| trace_mm_compaction_kcompactd_wake(pgdat->node_id, cc.order, |
| cc.highest_zoneidx); |
| count_compact_event(KCOMPACTD_WAKE); |
| |
| for (zoneid = 0; zoneid <= cc.highest_zoneidx; zoneid++) { |
| int status; |
| |
| zone = &pgdat->node_zones[zoneid]; |
| if (!populated_zone(zone)) |
| continue; |
| |
| if (compaction_deferred(zone, cc.order)) |
| continue; |
| |
| ret = compaction_suit_allocation_order(zone, |
| cc.order, zoneid, ALLOC_WMARK_MIN); |
| if (ret != COMPACT_CONTINUE) |
| continue; |
| |
| if (kthread_should_stop()) |
| return; |
| |
| cc.zone = zone; |
| status = compact_zone(&cc, NULL); |
| |
| if (status == COMPACT_SUCCESS) { |
| compaction_defer_reset(zone, cc.order, false); |
| } else if (status == COMPACT_PARTIAL_SKIPPED || status == COMPACT_COMPLETE) { |
| /* |
| * Buddy pages may become stranded on pcps that could |
| * otherwise coalesce on the zone's free area for |
| * order >= cc.order. This is ratelimited by the |
| * upcoming deferral. |
| */ |
| drain_all_pages(zone); |
| |
| /* |
| * 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); |
| } |
| |
| /* |
| * Regardless of success, we are done until woken up next. But remember |
| * the requested order/highest_zoneidx 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_highest_zoneidx >= cc.highest_zoneidx) |
| pgdat->kcompactd_highest_zoneidx = pgdat->nr_zones - 1; |
| } |
| |
| void wakeup_kcompactd(pg_data_t *pgdat, int order, int highest_zoneidx) |
| { |
| if (!order) |
| return; |
| |
| if (pgdat->kcompactd_max_order < order) |
| pgdat->kcompactd_max_order = order; |
| |
| if (pgdat->kcompactd_highest_zoneidx > highest_zoneidx) |
| pgdat->kcompactd_highest_zoneidx = highest_zoneidx; |
| |
| /* |
| * Pairs with implicit barrier in wait_event_freezable() |
| * such that wakeups are not missed. |
| */ |
| if (!wq_has_sleeper(&pgdat->kcompactd_wait)) |
| return; |
| |
| if (!kcompactd_node_suitable(pgdat)) |
| return; |
| |
| trace_mm_compaction_wakeup_kcompactd(pgdat->node_id, order, |
| highest_zoneidx); |
| 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; |
| long default_timeout = msecs_to_jiffies(HPAGE_FRAG_CHECK_INTERVAL_MSEC); |
| long timeout = default_timeout; |
| |
| 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_highest_zoneidx = pgdat->nr_zones - 1; |
| |
| while (!kthread_should_stop()) { |
| unsigned long pflags; |
| |
| /* |
| * Avoid the unnecessary wakeup for proactive compaction |
| * when it is disabled. |
| */ |
| if (!sysctl_compaction_proactiveness) |
| timeout = MAX_SCHEDULE_TIMEOUT; |
| trace_mm_compaction_kcompactd_sleep(pgdat->node_id); |
| if (wait_event_freezable_timeout(pgdat->kcompactd_wait, |
| kcompactd_work_requested(pgdat), timeout) && |
| !pgdat->proactive_compact_trigger) { |
| |
| psi_memstall_enter(&pflags); |
| kcompactd_do_work(pgdat); |
| psi_memstall_leave(&pflags); |
| /* |
| * Reset the timeout value. The defer timeout from |
| * proactive compaction is lost here but that is fine |
| * as the condition of the zone changing substantionally |
| * then carrying on with the previous defer interval is |
| * not useful. |
| */ |
| timeout = default_timeout; |
| continue; |
| } |
| |
| /* |
| * Start the proactive work with default timeout. Based |
| * on the fragmentation score, this timeout is updated. |
| */ |
| timeout = default_timeout; |
| if (should_proactive_compact_node(pgdat)) { |
| unsigned int prev_score, score; |
| |
| prev_score = fragmentation_score_node(pgdat); |
| compact_node(pgdat, true); |
| score = fragmentation_score_node(pgdat); |
| /* |
| * Defer proactive compaction if the fragmentation |
| * score did not go down i.e. no progress made. |
| */ |
| if (unlikely(score >= prev_score)) |
| timeout = |
| default_timeout << COMPACT_MAX_DEFER_SHIFT; |
| } |
| if (unlikely(pgdat->proactive_compact_trigger)) |
| pgdat->proactive_compact_trigger = false; |
| } |
| |
| 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. |
| */ |
| void __meminit kcompactd_run(int nid) |
| { |
| pg_data_t *pgdat = NODE_DATA(nid); |
| |
| if (pgdat->kcompactd) |
| return; |
| |
| 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); |
| pgdat->kcompactd = NULL; |
| } |
| } |
| |
| /* |
| * Called by memory hotplug when all memory in a node is offlined. Caller must |
| * be holding mem_hotplug_begin/done(). |
| */ |
| void __meminit 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) |
| { |
|