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- // 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 <[email protected]>
- */
- #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);
- }
- #else
- #define count_compact_event(item) do { } while (0)
- #define count_compact_events(item, delta) do { } while (0)
- #endif
- #if defined CONFIG_COMPACTION || defined CONFIG_CMA
- #define CREATE_TRACE_POINTS
- #include <trace/events/compaction.h>
- #undef CREATE_TRACE_POINTS
- #include <trace/hooks/compaction.h>
- #include <trace/hooks/mm.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 unsigned long release_freepages(struct list_head *freelist)
- {
- struct page *page, *next;
- unsigned long high_pfn = 0;
- list_for_each_entry_safe(page, next, freelist, lru) {
- unsigned long pfn = page_to_pfn(page);
- list_del(&page->lru);
- __free_page(page);
- if (pfn > high_pfn)
- high_pfn = pfn;
- }
- return high_pfn;
- }
- static void split_map_pages(struct list_head *list)
- {
- unsigned int i, order, nr_pages;
- struct page *page, *next;
- LIST_HEAD(tmp_list);
- list_for_each_entry_safe(page, next, list, lru) {
- list_del(&page->lru);
- order = page_private(page);
- nr_pages = 1 << order;
- post_alloc_hook(page, order, __GFP_MOVABLE);
- if (order)
- split_page(page, order);
- for (i = 0; i < nr_pages; i++) {
- list_add(&page->lru, &tmp_list);
- page++;
- }
- }
- list_splice(&tmp_list, list);
- }
- #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;
- }
- EXPORT_SYMBOL(PageMovable);
- 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);
- }
- /*
- * 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;
- 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;
- /* Only flush if a full compaction finished recently */
- if (zone->compact_blockskip_flush)
- __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,
- unsigned long pfn)
- {
- bool skip;
- /* Do no update if skip hint is being ignored */
- if (cc->ignore_skip_hint)
- return false;
- if (!pageblock_aligned(pfn))
- 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;
- pfn = pageblock_end_pfn(pfn);
- /* Set for isolation rather than compaction */
- if (cc->no_set_skip_hint)
- return;
- 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;
- if (!page)
- return;
- set_pageblock_skip(page);
- /* Update where async and sync compaction should restart */
- 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,
- unsigned long pfn)
- {
- 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 *cursor;
- 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;
- cursor = pfn_to_page(blockpfn);
- /* Isolate free pages. */
- for (; blockpfn < end_pfn; blockpfn += stride, cursor += stride) {
- int isolated;
- struct page *page = cursor;
- /*
- * Periodically drop the lock (if held) regardless of its
- * contention, to give chance to IRQs. Abort if fatal signal
- * pending.
- */
- 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 (likely(order < MAX_ORDER)) {
- blockpfn += (1UL << order) - 1;
- cursor += (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);
- if (!strict && cc->nr_migratepages <= cc->nr_freepages) {
- blockpfn += isolated;
- break;
- }
- /* Advance to the end of split page */
- blockpfn += isolated - 1;
- cursor += isolated - 1;
- continue;
- isolate_fail:
- if (strict)
- break;
- else
- continue;
- }
- if (locked)
- spin_unlock_irqrestore(&cc->zone->lock, flags);
- /*
- * There is a tiny chance that we have read bogus compound_order(),
- * so be careful to not go outside of the pageblock.
- */
- if (unlikely(blockpfn > end_pfn))
- blockpfn = end_pfn;
- trace_mm_compaction_isolate_freepages(*start_pfn, blockpfn,
- nr_scanned, total_isolated);
- /* Record how far we have got within the block */
- *start_pfn = blockpfn;
- /*
- * If strict isolation is requested by CMA then check that all the
- * pages requested were isolated. If there were any failures, 0 is
- * returned and CMA will fail.
- */
- if (strict && blockpfn < end_pfn)
- total_isolated = 0;
- 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;
- LIST_HEAD(freelist);
- pfn = start_pfn;
- block_start_pfn = pageblock_start_pfn(pfn);
- if (block_start_pfn < cc->zone->zone_start_pfn)
- block_start_pfn = cc->zone->zone_start_pfn;
- block_end_pfn = pageblock_end_pfn(pfn);
- for (; pfn < end_pfn; pfn += isolated,
- block_start_pfn = block_end_pfn,
- block_end_pfn += pageblock_nr_pages) {
- /* Protect pfn from changing by isolate_freepages_block */
- unsigned long isolate_start_pfn = pfn;
- block_end_pfn = min(block_end_pfn, end_pfn);
- /*
- * pfn could pass the block_end_pfn if isolated freepage
- * is more than pageblock order. In this case, we adjust
- * scanning range to right one.
- */
- if (pfn >= block_end_pfn) {
- block_start_pfn = pageblock_start_pfn(pfn);
- block_end_pfn = pageblock_end_pfn(pfn);
- block_end_pfn = min(block_end_pfn, end_pfn);
- }
- if (!pageblock_pfn_to_page(block_start_pfn,
- block_end_pfn, cc->zone))
- break;
- isolated = isolate_freepages_block(cc, &isolate_start_pfn,
- block_end_pfn, &freelist, 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).
- */
- }
- /* __isolate_free_page() does not map the pages */
- split_map_pages(&freelist);
- if (pfn < end_pfn) {
- /* Loop terminated early, cleanup. */
- release_freepages(&freelist);
- return 0;
- }
- /* We don't use freelists for anything. */
- return pfn;
- }
- #ifdef CONFIG_COMPACTION
- unsigned long isolate_and_split_free_page(struct page *page,
- struct list_head *list)
- {
- unsigned long isolated;
- unsigned int order;
- if (!PageBuddy(page))
- return 0;
- order = buddy_order(page);
- isolated = __isolate_free_page(page, order);
- if (!isolated)
- return 0;
- set_page_private(page, order);
- list_add(&page->lru, list);
- split_map_pages(list);
- return isolated;
- }
- EXPORT_SYMBOL_GPL(isolate_and_split_free_page);
- #endif
- /* Similar to reclaim, but different enough that they don't share logic */
- static bool too_many_isolated(pg_data_t *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);
- too_many = isolated > (inactive + active) / 2;
- if (!too_many)
- wake_throttle_isolated(pgdat);
- return too_many;
- }
- /**
- * 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 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(pgdat))) {
- /* 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++) {
- 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 aligned 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)) {
- if (!isolation_suitable(cc, page)) {
- low_pfn = end_pfn;
- page = NULL;
- goto isolate_abort;
- }
- valid_page = page;
- }
- if (PageHuge(page) && cc->alloc_contig) {
- 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;
- goto isolate_fail;
- }
- if (PageHuge(page)) {
- /*
- * Hugepage was successfully isolated and placed
- * on the cc->migratepages list.
- */
- low_pfn += compound_nr(page) - 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_ORDER)
- low_pfn += (1UL << freepage_order) - 1;
- continue;
- }
- /*
- * Regardless of being on LRU, compound pages such as THP and
- * hugetlbfs are not to be compacted unless we are attempting
- * an allocation much larger than the huge page size (eg CMA).
- * 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);
- if (likely(order < MAX_ORDER))
- low_pfn += (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))
- 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.
- */
- if (unlikely(!get_page_unless_zero(page)))
- 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 = page_mapping(page);
- if (!mapping && (page_count(page) - 1) > total_mapcount(page))
- 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 (!PageLRU(page))
- goto isolate_fail_put;
- /* Compaction might skip unevictable pages but CMA takes them */
- if (!(mode & ISOLATE_UNEVICTABLE) && PageUnevictable(page))
- 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) && PageWriteback(page))
- goto isolate_fail_put;
- if ((mode & ISOLATE_ASYNC_MIGRATE) && PageDirty(page)) {
- bool migrate_dirty;
- /*
- * Only pages without mappings or that have a
- * ->migrate_folio callback are possible to migrate
- * without blocking. However, we can be racing with
- * truncation so it's necessary to lock the page
- * to stabilise the mapping as truncation holds
- * the page lock until after the page is removed
- * from the page cache.
- */
- if (!trylock_page(page))
- goto isolate_fail_put;
- mapping = page_mapping(page);
- migrate_dirty = !mapping ||
- mapping->a_ops->migrate_folio;
- unlock_page(page);
- if (!migrate_dirty)
- goto isolate_fail_put;
- }
- /* Try isolate the page */
- if (!TestClearPageLRU(page))
- goto isolate_fail_put;
- lruvec = folio_lruvec(page_folio(page));
- /* 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, page_folio(page));
- /* Try get exclusive access under lock */
- if (!skip_updated) {
- skip_updated = true;
- if (test_and_set_skip(cc, page, low_pfn))
- goto isolate_abort;
- }
- /*
- * Page become compound since the non-locked check,
- * and it's on LRU. It can only be a THP so the order
- * is safe to read and it's 0 for tail pages.
- */
- if (unlikely(PageCompound(page) && !cc->alloc_contig)) {
- low_pfn += compound_nr(page) - 1;
- SetPageLRU(page);
- goto isolate_fail_put;
- }
- }
- /* The whole page is taken off the LRU; skip the tail pages. */
- if (PageCompound(page))
- low_pfn += compound_nr(page) - 1;
- /* Successfully isolated */
- del_page_from_lru_list(page, lruvec);
- mod_node_page_state(page_pgdat(page),
- NR_ISOLATED_ANON + page_is_file_lru(page),
- thp_nr_pages(page));
- isolate_success:
- list_add(&page->lru, &cc->migratepages);
- isolate_success_no_list:
- cc->nr_migratepages += compound_nr(page);
- nr_isolated += compound_nr(page);
- nr_scanned += compound_nr(page) - 1;
- /*
- * Avoid isolating too much unless this block is being
- * rescanned (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->rescan && !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;
- }
- put_page(page);
- 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;
- page = NULL;
- isolate_abort:
- if (locked)
- unlock_page_lruvec_irqrestore(locked, flags);
- if (page) {
- SetPageLRU(page);
- put_page(page);
- }
- /*
- * Updated 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->rescan)) {
- if (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)) {
- /*
- * 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) >= pageblock_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_last(freelist, &freepage->lru)) {
- list_cut_before(&sublist, freelist, &freepage->lru);
- 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_first(freelist, &freepage->lru)) {
- list_cut_position(&sublist, freelist, &freepage->lru);
- 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 (cc->nr_freepages < cc->nr_migratepages)
- set_pageblock_skip(page);
- return;
- }
- /* 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 unsigned long
- fast_isolate_freepages(struct compact_control *cc)
- {
- unsigned int limit = max(1U, freelist_scan_limit(cc) >> 1);
- unsigned int nr_scanned = 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 cc->free_pfn;
- /*
- * 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, lru) {
- 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 minimum 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;
- cc->nr_freepages += nr_isolated;
- list_add_tail(&page->lru, &cc->freepages);
- 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);
- /*
- * Smaller scan on next order so the total scan is related
- * to freelist_scan_limit.
- */
- if (order_scanned >= limit)
- limit = max(1U, limit >> 1);
- }
- 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);
- 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 cc->free_pfn;
- low_pfn = page_to_pfn(page);
- fast_isolate_around(cc, low_pfn);
- return 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 */
- struct list_head *freelist = &cc->freepages;
- unsigned int stride;
- /* Try a small search of the free lists for a candidate */
- fast_isolate_freepages(cc);
- if (cc->nr_freepages)
- goto splitmap;
- /*
- * 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)
- 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, freelist, 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);
- /* 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;
- splitmap:
- /* __isolate_free_page() does not map the pages */
- split_map_pages(freelist);
- }
- /*
- * This is a migrate-callback that "allocates" freepages by taking pages
- * from the isolated freelists in the block we are migrating to.
- */
- static struct page *compaction_alloc(struct page *migratepage,
- unsigned long data)
- {
- struct compact_control *cc = (struct compact_control *)data;
- struct page *freepage;
- if (list_empty(&cc->freepages)) {
- isolate_freepages(cc);
- if (list_empty(&cc->freepages))
- return NULL;
- }
- freepage = list_entry(cc->freepages.next, struct page, lru);
- list_del(&freepage->lru);
- cc->nr_freepages--;
- return freepage;
- }
- /*
- * This is a migrate-callback that "frees" freepages back to the isolated
- * freelist. All pages on the freelist are from the same zone, so there is no
- * special handling needed for NUMA.
- */
- static void compaction_free(struct page *page, unsigned long data)
- {
- struct compact_control *cc = (struct compact_control *)data;
- list_add(&page->lru, &cc->freepages);
- cc->nr_freepages++;
- }
- /* possible outcome of isolate_migratepages */
- typedef enum {
- ISOLATE_ABORT, /* Abort compaction now */
- ISOLATE_NONE, /* No pages isolated, continue scanning */
- ISOLATE_SUCCESS, /* Pages isolated, migrate */
- } isolate_migrate_t;
- /*
- * Allow userspace to control policy on scanning the unevictable LRU for
- * compactable pages.
- */
- int sysctl_compact_unevictable_allowed __read_mostly = CONFIG_COMPACT_UNEVICTABLE_DEFAULT;
- 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 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, lru) {
- 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;
- set_pageblock_skip(freepage);
- 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 marks a pageblock skipped so to avoid
- * the isolation_suitable check below, 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)
- 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) &&
- !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;
- }
- /*
- * order == -1 is expected when compacting via
- * /proc/sys/vm/compact_memory
- */
- static inline bool is_via_compact_memory(int order)
- {
- return order == -1;
- }
- /*
- * 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];
- score += fragmentation_score_zone_weighted(zone);
- }
- return score;
- }
- static unsigned int fragmentation_score_wmark(pg_data_t *pgdat, 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(pgdat, 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(pgdat, 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 < MAX_ORDER; 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 enum compact_result __compaction_suitable(struct zone *zone, int order,
- unsigned int alloc_flags,
- int highest_zoneidx,
- unsigned long wmark_target)
- {
- unsigned long watermark;
- if (is_via_compact_memory(order))
- return COMPACT_CONTINUE;
- watermark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK);
- /*
- * If watermarks for high-order allocation are already met, there
- * should be no need for compaction at all.
- */
- if (zone_watermark_ok(zone, order, watermark, highest_zoneidx,
- alloc_flags))
- return COMPACT_SUCCESS;
- /*
- * Watermarks for order-0 must be met for compaction to be able to
- * isolate free pages for migration targets. This means that the
- * watermark and alloc_flags have to match, or be more pessimistic than
- * the check in __isolate_free_page(). We don't use the direct
- * compactor's alloc_flags, as they are not relevant for freepage
- * isolation. We however do use the direct compactor's 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);
- if (!__zone_watermark_ok(zone, 0, watermark, highest_zoneidx,
- ALLOC_CMA, wmark_target))
- return COMPACT_SKIPPED;
- return COMPACT_CONTINUE;
- }
- /*
- * compaction_suitable: Is this suitable to run compaction on this zone now?
- * Returns
- * COMPACT_SKIPPED - If there are too few free pages for compaction
- * COMPACT_SUCCESS - If the allocation would succeed without compaction
- * COMPACT_CONTINUE - If compaction should run now
- */
- enum compact_result compaction_suitable(struct zone *zone, int order,
- unsigned int alloc_flags,
- int highest_zoneidx)
- {
- enum compact_result ret;
- int fragindex;
- ret = __compaction_suitable(zone, order, alloc_flags, 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 (ret == COMPACT_CONTINUE && (order > PAGE_ALLOC_COSTLY_ORDER)) {
- fragindex = fragmentation_index(zone, order);
- if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold)
- ret = COMPACT_NOT_SUITABLE_ZONE;
- }
- trace_mm_compaction_suitable(zone, order, ret);
- if (ret == COMPACT_NOT_SUITABLE_ZONE)
- ret = COMPACT_SKIPPED;
- return ret;
- }
- bool compaction_zonelist_suitable(struct alloc_context *ac, int order,
- int alloc_flags)
- {
- struct zone *zone;
- struct zoneref *z;
- /*
- * Make sure at least one zone would pass __compaction_suitable if we continue
- * retrying the reclaim.
- */
- for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
- ac->highest_zoneidx, ac->nodemask) {
- unsigned long available;
- enum compact_result compact_result;
- /*
- * Do not consider all the reclaimable memory because we do not
- * want to trash just for a single high order allocation which
- * is even not guaranteed to appear even if __compaction_suitable
- * is happy about the watermark check.
- */
- available = zone_reclaimable_pages(zone) / order;
- available += zone_page_state_snapshot(zone, NR_FREE_PAGES);
- compact_result = __compaction_suitable(zone, order, alloc_flags,
- ac->highest_zoneidx, available);
- if (compact_result == COMPACT_CONTINUE)
- return true;
- }
- return false;
- }
- 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;
- long vendor_ret;
- /*
- * 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;
- INIT_LIST_HEAD(&cc->freepages);
- INIT_LIST_HEAD(&cc->migratepages);
- cc->migratetype = gfp_migratetype(cc->gfp_mask);
- ret = compaction_suitable(cc->zone, cc->order, cc->alloc_flags,
- cc->highest_zoneidx);
- /* Compaction is likely to fail */
- if (ret == COMPACT_SUCCESS || ret == COMPACT_SKIPPED)
- return ret;
- /* huh, compaction_suitable is returning something unexpected */
- VM_BUG_ON(ret != COMPACT_CONTINUE);
- /*
- * Clear pageblock skip if there were failures recently and compaction
- * is about to be retried after being deferred.
- */
- if (compaction_restarting(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);
- trace_android_vh_mm_compaction_begin(cc, &vendor_ret);
- /* 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 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->rescan = false;
- if (pageblock_start_pfn(last_migrated_pfn) ==
- pageblock_start_pfn(iteration_start_pfn)) {
- cc->rescan = true;
- }
- 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 = iteration_start_pfn;
- }
- err = migrate_pages(&cc->migratepages, compaction_alloc,
- compaction_free, (unsigned long)cc, cc->mode,
- MR_COMPACTION, &nr_succeeded);
- trace_mm_compaction_migratepages(cc, 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;
- }
- /*
- * We failed to migrate at least one page in the current
- * order-aligned block, so skip the rest of it.
- */
- if (cc->direct_compaction &&
- (cc->mode == MIGRATE_ASYNC)) {
- cc->migrate_pfn = block_end_pfn(
- cc->migrate_pfn - 1, cc->order);
- /* Draining pcplists is useless in this case */
- last_migrated_pfn = 0;
- }
- }
- check_drain:
- /*
- * Has the migration scanner moved away from the previous
- * cc->order aligned block where we migrated from? If yes,
- * flush the pages that were freed, so that they can merge and
- * compact_finished() can detect immediately if allocation
- * would succeed.
- */
- if (cc->order > 0 && 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;
- }
- }
- /* Stop if a page has been captured */
- if (capc && capc->page) {
- ret = COMPACT_SUCCESS;
- break;
- }
- }
- out:
- /*
- * Release free pages and update where the free scanner should restart,
- * so we don't leave any returned pages behind in the next attempt.
- */
- if (cc->nr_freepages > 0) {
- unsigned long free_pfn = release_freepages(&cc->freepages);
- cc->nr_freepages = 0;
- VM_BUG_ON(free_pfn == 0);
- /* The cached pfn is always the first in a pageblock */
- free_pfn = pageblock_start_pfn(free_pfn);
- /*
- * Only go back, not forward. The cached pfn might have been
- * already reset to zone end in compact_finished()
- */
- if (free_pfn > 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_android_vh_mm_compaction_end(cc, vendor_ret);
- trace_mm_compaction_end(cc, start_pfn, end_pfn, sync, ret);
- return ret;
- }
- static enum compact_result compact_zone_order(struct zone *zone, int order,
- gfp_t gfp_mask, enum compact_priority prio,
- unsigned int alloc_flags, int 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);
- VM_BUG_ON(!list_empty(&cc.freepages));
- VM_BUG_ON(!list_empty(&cc.migratepages));
- /*
- * 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;
- }
- int sysctl_extfrag_threshold = 500;
- /**
- * try_to_compact_pages - Direct compact to satisfy a high-order allocation
- * @gfp_mask: The GFP mask of the current allocation
- * @order: The order of the current allocation
- * @alloc_flags: The allocation flags of the current allocation
- * @ac: The context of current allocation
- * @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)
- {
- int may_perform_io = (__force int)(gfp_mask & __GFP_IO);
- struct zoneref *z;
- struct zone *zone;
- enum compact_result rc = COMPACT_SKIPPED;
- /*
- * Check if the GFP flags allow compaction - GFP_NOIO is really
- * tricky context because the migration might require IO
- */
- if (!may_perform_io)
- return COMPACT_SKIPPED;
- trace_mm_compaction_try_to_compact_pages(order, gfp_mask, prio);
- /* Compact each zone in the list */
- for_each_zone_zonelist_nodemask(zone, z, ac->zonelist,
- ac->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;
- }
- trace_android_vh_compaction_try_to_compact_pages_exit(&rc);
- return rc;
- }
- /*
- * Compact all zones within a node 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 void proactive_compact_node(pg_data_t *pgdat)
- {
- int zoneid;
- struct zone *zone;
- struct compact_control cc = {
- .order = -1,
- .mode = MIGRATE_SYNC_LIGHT,
- .ignore_skip_hint = true,
- .whole_zone = true,
- .gfp_mask = GFP_KERNEL,
- .proactive_compaction = true,
- };
- for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
- zone = &pgdat->node_zones[zoneid];
- if (!populated_zone(zone))
- continue;
- cc.zone = zone;
- compact_zone(&cc, NULL);
- VM_BUG_ON(!list_empty(&cc.freepages));
- VM_BUG_ON(!list_empty(&cc.migratepages));
- }
- }
- /* Compact all zones within a node */
- static void compact_node(int nid)
- {
- pg_data_t *pgdat = NODE_DATA(nid);
- int zoneid;
- struct zone *zone;
- struct compact_control cc = {
- .order = -1,
- .mode = MIGRATE_SYNC,
- .ignore_skip_hint = true,
- .whole_zone = true,
- .gfp_mask = GFP_KERNEL,
- };
- for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) {
- zone = &pgdat->node_zones[zoneid];
- if (!populated_zone(zone))
- continue;
- cc.zone = zone;
- compact_zone(&cc, NULL);
- VM_BUG_ON(!list_empty(&cc.freepages));
- VM_BUG_ON(!list_empty(&cc.migratepages));
- }
- }
- /* Compact all nodes in the system */
- static void compact_nodes(void)
- {
- int nid;
- /* Flush pending updates to the LRU lists */
- lru_add_drain_all();
- for_each_online_node(nid)
- compact_node(nid);
- }
- /*
- * Tunable for proactive compaction. It determines how
- * aggressively the kernel should compact memory in the
- * background. It takes values in the range [0, 100].
- */
- unsigned int __read_mostly sysctl_compaction_proactiveness = 20;
- int compaction_proactiveness_sysctl_handler(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;
- wake_up_interruptible(&pgdat->kcompactd_wait);
- }
- }
- return 0;
- }
- /*
- * This is the entry point for compacting all nodes via
- * /proc/sys/vm/compact_memory
- */
- int sysctl_compaction_handler(struct ctl_table *table, int write,
- void *buffer, size_t *length, loff_t *ppos)
- {
- if (write)
- compact_nodes();
- return 0;
- }
- #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(nid);
- }
- 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)
- {
- return device_remove_file(&node->dev, &dev_attr_compact);
- }
- #endif /* CONFIG_SYSFS && CONFIG_NUMA */
- static inline bool kcompactd_work_requested(pg_data_t *pgdat)
- {
- return pgdat->kcompactd_max_order > 0 || kthread_should_stop() ||
- 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;
- for (zoneid = 0; zoneid <= highest_zoneidx; zoneid++) {
- zone = &pgdat->node_zones[zoneid];
- if (!populated_zone(zone))
- continue;
- if (compaction_suitable(zone, pgdat->kcompactd_max_order, 0,
- highest_zoneidx) == 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,
- };
- 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;
- if (compaction_suitable(zone, cc.order, 0, zoneid) !=
- 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);
- VM_BUG_ON(!list_empty(&cc.freepages));
- VM_BUG_ON(!list_empty(&cc.migratepages));
- }
- trace_android_vh_compaction_exit(pgdat->node_id, cc.order, cc.highest_zoneidx);
- /*
- * 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);
- proactive_compact_node(pgdat);
- 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 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 kcompactd_stop(int nid)
- {
- struct task_struct *kcompactd = NODE_DATA(nid)->kcompactd;
- if (kcompactd) {
- kthread_stop(kcompactd);
- NODE_DATA(nid)->kcompactd = NULL;
- }
- }
- /*
- * It's optimal to keep kcompactd on the same CPUs as their memory, but
- * not required for correctness. So if the last cpu in a node goes
- * away, we get changed to run anywhere: as the first one comes back,
- * restore their cpu bindings.
- */
- static int kcompactd_cpu_online(unsigned int cpu)
- {
- int nid;
- for_each_node_state(nid, N_MEMORY) {
- pg_data_t *pgdat = NODE_DATA(nid);
- const struct cpumask *mask;
- mask = cpumask_of_node(pgdat->node_id);
- if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids)
- /* One of our CPUs online: restore mask */
- if (pgdat->kcompactd)
- set_cpus_allowed_ptr(pgdat->kcompactd, mask);
- }
- return 0;
- }
- static int __init kcompactd_init(void)
- {
- int nid;
- int ret;
- ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
- "mm/compaction:online",
- kcompactd_cpu_online, NULL);
- if (ret < 0) {
- pr_err("kcompactd: failed to register hotplug callbacks.\n");
- return ret;
- }
- for_each_node_state(nid, N_MEMORY)
- kcompactd_run(nid);
- return 0;
- }
- subsys_initcall(kcompactd_init)
- #endif /* CONFIG_COMPACTION */
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