| /* |
| * linux/mm/compaction.c |
| * |
| * Memory compaction for the reduction of external fragmentation. Note that |
| * this heavily depends upon page migration to do all the real heavy |
| * lifting |
| * |
| * Copyright IBM Corp. 2007-2010 Mel Gorman <mel@csn.ul.ie> |
| */ |
| #include <linux/swap.h> |
| #include <linux/migrate.h> |
| #include <linux/compaction.h> |
| #include <linux/mm_inline.h> |
| #include <linux/backing-dev.h> |
| #include <linux/sysctl.h> |
| #include <linux/sysfs.h> |
| #include <linux/balloon_compaction.h> |
| #include <linux/page-isolation.h> |
| #include "internal.h" |
| |
| #ifdef CONFIG_COMPACTION |
| static inline void count_compact_event(enum vm_event_item item) |
| { |
| count_vm_event(item); |
| } |
| |
| static inline void count_compact_events(enum vm_event_item item, long delta) |
| { |
| count_vm_events(item, delta); |
| } |
| #else |
| #define count_compact_event(item) do { } while (0) |
| #define count_compact_events(item, delta) do { } while (0) |
| #endif |
| |
| #if defined CONFIG_COMPACTION || defined CONFIG_CMA |
| |
| #define CREATE_TRACE_POINTS |
| #include <trace/events/compaction.h> |
| |
| static unsigned long release_freepages(struct list_head *freelist) |
| { |
| struct page *page, *next; |
| unsigned long count = 0; |
| |
| list_for_each_entry_safe(page, next, freelist, lru) { |
| list_del(&page->lru); |
| __free_page(page); |
| count++; |
| } |
| |
| return count; |
| } |
| |
| static void map_pages(struct list_head *list) |
| { |
| struct page *page; |
| |
| list_for_each_entry(page, list, lru) { |
| arch_alloc_page(page, 0); |
| kernel_map_pages(page, 1, 1); |
| } |
| } |
| |
| static inline bool migrate_async_suitable(int migratetype) |
| { |
| return is_migrate_cma(migratetype) || migratetype == MIGRATE_MOVABLE; |
| } |
| |
| #ifdef CONFIG_COMPACTION |
| /* 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); |
| } |
| |
| /* |
| * This function is called to clear all cached information on pageblocks that |
| * should be skipped for page isolation when the migrate and free page scanner |
| * meet. |
| */ |
| static void __reset_isolation_suitable(struct zone *zone) |
| { |
| unsigned long start_pfn = zone->zone_start_pfn; |
| unsigned long end_pfn = zone_end_pfn(zone); |
| unsigned long pfn; |
| |
| zone->compact_cached_migrate_pfn = start_pfn; |
| zone->compact_cached_free_pfn = end_pfn; |
| zone->compact_blockskip_flush = false; |
| |
| /* Walk the zone and mark every pageblock as suitable for isolation */ |
| for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) { |
| struct page *page; |
| |
| cond_resched(); |
| |
| if (!pfn_valid(pfn)) |
| continue; |
| |
| page = pfn_to_page(pfn); |
| if (zone != page_zone(page)) |
| continue; |
| |
| clear_pageblock_skip(page); |
| } |
| } |
| |
| void reset_isolation_suitable(pg_data_t *pgdat) |
| { |
| int zoneid; |
| |
| for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { |
| struct zone *zone = &pgdat->node_zones[zoneid]; |
| if (!populated_zone(zone)) |
| continue; |
| |
| /* Only flush if a full compaction finished recently */ |
| if (zone->compact_blockskip_flush) |
| __reset_isolation_suitable(zone); |
| } |
| } |
| |
| /* |
| * If no pages were isolated then mark this pageblock to be skipped in the |
| * future. The information is later cleared by __reset_isolation_suitable(). |
| */ |
| static void update_pageblock_skip(struct compact_control *cc, |
| struct page *page, unsigned long nr_isolated, |
| bool migrate_scanner) |
| { |
| struct zone *zone = cc->zone; |
| |
| if (cc->ignore_skip_hint) |
| return; |
| |
| if (!page) |
| return; |
| |
| if (!nr_isolated) { |
| unsigned long pfn = page_to_pfn(page); |
| set_pageblock_skip(page); |
| |
| /* Update where compaction should restart */ |
| if (migrate_scanner) { |
| if (!cc->finished_update_migrate && |
| pfn > zone->compact_cached_migrate_pfn) |
| zone->compact_cached_migrate_pfn = pfn; |
| } else { |
| if (!cc->finished_update_free && |
| pfn < zone->compact_cached_free_pfn) |
| zone->compact_cached_free_pfn = pfn; |
| } |
| } |
| } |
| #else |
| static inline bool isolation_suitable(struct compact_control *cc, |
| struct page *page) |
| { |
| return true; |
| } |
| |
| static void update_pageblock_skip(struct compact_control *cc, |
| struct page *page, unsigned long nr_isolated, |
| bool migrate_scanner) |
| { |
| } |
| #endif /* CONFIG_COMPACTION */ |
| |
| static inline bool should_release_lock(spinlock_t *lock) |
| { |
| return need_resched() || spin_is_contended(lock); |
| } |
| |
| /* |
| * Compaction requires the taking of some coarse locks that are potentially |
| * very heavily contended. Check if the process needs to be scheduled or |
| * if the lock is contended. For async compaction, back out in the event |
| * if contention is severe. For sync compaction, schedule. |
| * |
| * Returns true if the lock is held. |
| * Returns false if the lock is released and compaction should abort |
| */ |
| static bool compact_checklock_irqsave(spinlock_t *lock, unsigned long *flags, |
| bool locked, struct compact_control *cc) |
| { |
| if (should_release_lock(lock)) { |
| if (locked) { |
| spin_unlock_irqrestore(lock, *flags); |
| locked = false; |
| } |
| |
| /* async aborts if taking too long or contended */ |
| if (!cc->sync) { |
| cc->contended = true; |
| return false; |
| } |
| |
| cond_resched(); |
| } |
| |
| if (!locked) |
| spin_lock_irqsave(lock, *flags); |
| return true; |
| } |
| |
| static inline bool compact_trylock_irqsave(spinlock_t *lock, |
| unsigned long *flags, struct compact_control *cc) |
| { |
| return compact_checklock_irqsave(lock, flags, false, cc); |
| } |
| |
| /* Returns true if the page is within a block suitable for migration to */ |
| static bool suitable_migration_target(struct page *page) |
| { |
| int migratetype = get_pageblock_migratetype(page); |
| |
| /* Don't interfere with memory hot-remove or the min_free_kbytes blocks */ |
| if (migratetype == MIGRATE_RESERVE) |
| return false; |
| |
| if (is_migrate_isolate(migratetype)) |
| return false; |
| |
| /* If the page is a large free page, then allow migration */ |
| if (PageBuddy(page) && page_order(page) >= pageblock_order) |
| return true; |
| |
| /* If the block is MIGRATE_MOVABLE or MIGRATE_CMA, allow migration */ |
| if (migrate_async_suitable(migratetype)) |
| return true; |
| |
| /* Otherwise skip the block */ |
| return false; |
| } |
| |
| /* |
| * Isolate free pages onto a private freelist. Caller must hold zone->lock. |
| * 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 blockpfn, |
| unsigned long end_pfn, |
| struct list_head *freelist, |
| bool strict) |
| { |
| int nr_scanned = 0, total_isolated = 0; |
| struct page *cursor, *valid_page = NULL; |
| unsigned long flags; |
| bool locked = false; |
| |
| cursor = pfn_to_page(blockpfn); |
| |
| /* Isolate free pages. */ |
| for (; blockpfn < end_pfn; blockpfn++, cursor++) { |
| int isolated, i; |
| struct page *page = cursor; |
| |
| nr_scanned++; |
| if (!pfn_valid_within(blockpfn)) |
| goto isolate_fail; |
| |
| if (!valid_page) |
| valid_page = page; |
| if (!PageBuddy(page)) |
| goto isolate_fail; |
| |
| /* |
| * The zone lock must be held to isolate freepages. |
| * Unfortunately this is a very coarse lock and can be |
| * heavily contended if there are parallel allocations |
| * or parallel compactions. For async compaction do not |
| * spin on the lock and we acquire the lock as late as |
| * possible. |
| */ |
| locked = compact_checklock_irqsave(&cc->zone->lock, &flags, |
| locked, cc); |
| if (!locked) |
| break; |
| |
| /* Recheck this is a suitable migration target under lock */ |
| if (!strict && !suitable_migration_target(page)) |
| break; |
| |
| /* Recheck this is a buddy page under lock */ |
| if (!PageBuddy(page)) |
| goto isolate_fail; |
| |
| /* Found a free page, break it into order-0 pages */ |
| isolated = split_free_page(page); |
| total_isolated += isolated; |
| for (i = 0; i < isolated; i++) { |
| list_add(&page->lru, freelist); |
| page++; |
| } |
| |
| /* If a page was split, advance to the end of it */ |
| if (isolated) { |
| blockpfn += isolated - 1; |
| cursor += isolated - 1; |
| continue; |
| } |
| |
| isolate_fail: |
| if (strict) |
| break; |
| else |
| continue; |
| |
| } |
| |
| trace_mm_compaction_isolate_freepages(nr_scanned, total_isolated); |
| |
| /* |
| * 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; |
| |
| if (locked) |
| spin_unlock_irqrestore(&cc->zone->lock, flags); |
| |
| /* Update the pageblock-skip if the whole pageblock was scanned */ |
| if (blockpfn == end_pfn) |
| update_pageblock_skip(cc, valid_page, total_isolated, false); |
| |
| count_compact_events(COMPACTFREE_SCANNED, nr_scanned); |
| if (total_isolated) |
| count_compact_events(COMPACTISOLATED, total_isolated); |
| return total_isolated; |
| } |
| |
| /** |
| * isolate_freepages_range() - isolate free pages. |
| * @start_pfn: The first PFN to start isolating. |
| * @end_pfn: The one-past-last PFN. |
| * |
| * Non-free pages, invalid PFNs, or zone boundaries within the |
| * [start_pfn, end_pfn) range are considered errors, cause function to |
| * undo its actions and return zero. |
| * |
| * Otherwise, function returns one-past-the-last PFN of isolated page |
| * (which may be greater then end_pfn if end fell in a middle of |
| * a free page). |
| */ |
| unsigned long |
| isolate_freepages_range(struct compact_control *cc, |
| unsigned long start_pfn, unsigned long end_pfn) |
| { |
| unsigned long isolated, pfn, block_end_pfn; |
| LIST_HEAD(freelist); |
| |
| for (pfn = start_pfn; pfn < end_pfn; pfn += isolated) { |
| if (!pfn_valid(pfn) || cc->zone != page_zone(pfn_to_page(pfn))) |
| break; |
| |
| /* |
| * On subsequent iterations ALIGN() is actually not needed, |
| * but we keep it that we not to complicate the code. |
| */ |
| block_end_pfn = ALIGN(pfn + 1, pageblock_nr_pages); |
| block_end_pfn = min(block_end_pfn, end_pfn); |
| |
| isolated = isolate_freepages_block(cc, pfn, block_end_pfn, |
| &freelist, true); |
| |
| /* |
| * In strict mode, isolate_freepages_block() returns 0 if |
| * there are any holes in the block (ie. invalid PFNs or |
| * non-free pages). |
| */ |
| if (!isolated) |
| break; |
| |
| /* |
| * If we managed to isolate pages, it is always (1 << n) * |
| * pageblock_nr_pages for some non-negative n. (Max order |
| * page may span two pageblocks). |
| */ |
| } |
| |
| /* split_free_page does not map the pages */ |
| map_pages(&freelist); |
| |
| if (pfn < end_pfn) { |
| /* Loop terminated early, cleanup. */ |
| release_freepages(&freelist); |
| return 0; |
| } |
| |
| /* We don't use freelists for anything. */ |
| return pfn; |
| } |
| |
| /* Update the number of anon and file isolated pages in the zone */ |
| static void acct_isolated(struct zone *zone, bool locked, struct compact_control *cc) |
| { |
| struct page *page; |
| unsigned int count[2] = { 0, }; |
| |
| list_for_each_entry(page, &cc->migratepages, lru) |
| count[!!page_is_file_cache(page)]++; |
| |
| /* If locked we can use the interrupt unsafe versions */ |
| if (locked) { |
| __mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]); |
| __mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]); |
| } else { |
| mod_zone_page_state(zone, NR_ISOLATED_ANON, count[0]); |
| mod_zone_page_state(zone, NR_ISOLATED_FILE, count[1]); |
| } |
| } |
| |
| /* Similar to reclaim, but different enough that they don't share logic */ |
| static bool too_many_isolated(struct zone *zone) |
| { |
| unsigned long active, inactive, isolated; |
| |
| inactive = zone_page_state(zone, NR_INACTIVE_FILE) + |
| zone_page_state(zone, NR_INACTIVE_ANON); |
| active = zone_page_state(zone, NR_ACTIVE_FILE) + |
| zone_page_state(zone, NR_ACTIVE_ANON); |
| isolated = zone_page_state(zone, NR_ISOLATED_FILE) + |
| zone_page_state(zone, NR_ISOLATED_ANON); |
| |
| return isolated > (inactive + active) / 2; |
| } |
| |
| /** |
| * isolate_migratepages_range() - isolate all migrate-able pages in range. |
| * @zone: Zone pages are in. |
| * @cc: Compaction control structure. |
| * @low_pfn: The first PFN of the range. |
| * @end_pfn: The one-past-the-last PFN of the range. |
| * @unevictable: true if it allows to isolate unevictable pages |
| * |
| * Isolate all pages that can be migrated from the range specified by |
| * [low_pfn, end_pfn). Returns zero if there is a fatal signal |
| * pending), otherwise PFN of the first page that was not scanned |
| * (which may be both less, equal to or more then end_pfn). |
| * |
| * Assumes that cc->migratepages is empty and cc->nr_migratepages is |
| * zero. |
| * |
| * Apart from cc->migratepages and cc->nr_migratetypes this function |
| * does not modify any cc's fields, in particular it does not modify |
| * (or read for that matter) cc->migrate_pfn. |
| */ |
| unsigned long |
| isolate_migratepages_range(struct zone *zone, struct compact_control *cc, |
| unsigned long low_pfn, unsigned long end_pfn, bool unevictable) |
| { |
| unsigned long last_pageblock_nr = 0, pageblock_nr; |
| unsigned long nr_scanned = 0, nr_isolated = 0; |
| struct list_head *migratelist = &cc->migratepages; |
| isolate_mode_t mode = 0; |
| struct lruvec *lruvec; |
| unsigned long flags; |
| bool locked = false; |
| struct page *page = NULL, *valid_page = NULL; |
| |
| /* |
| * Ensure that there are not too many pages isolated from the LRU |
| * list by either parallel reclaimers or compaction. If there are, |
| * delay for some time until fewer pages are isolated |
| */ |
| while (unlikely(too_many_isolated(zone))) { |
| /* async migration should just abort */ |
| if (!cc->sync) |
| return 0; |
| |
| congestion_wait(BLK_RW_ASYNC, HZ/10); |
| |
| if (fatal_signal_pending(current)) |
| return 0; |
| } |
| |
| /* Time to isolate some pages for migration */ |
| cond_resched(); |
| for (; low_pfn < end_pfn; low_pfn++) { |
| /* give a chance to irqs before checking need_resched() */ |
| if (locked && !((low_pfn+1) % SWAP_CLUSTER_MAX)) { |
| if (should_release_lock(&zone->lru_lock)) { |
| spin_unlock_irqrestore(&zone->lru_lock, flags); |
| locked = false; |
| } |
| } |
| |
| /* |
| * migrate_pfn does not necessarily start aligned to a |
| * pageblock. Ensure that pfn_valid is called when moving |
| * into a new MAX_ORDER_NR_PAGES range in case of large |
| * memory holes within the zone |
| */ |
| if ((low_pfn & (MAX_ORDER_NR_PAGES - 1)) == 0) { |
| if (!pfn_valid(low_pfn)) { |
| low_pfn += MAX_ORDER_NR_PAGES - 1; |
| continue; |
| } |
| } |
| |
| if (!pfn_valid_within(low_pfn)) |
| continue; |
| nr_scanned++; |
| |
| /* |
| * Get the page and ensure the page is within the same zone. |
| * See the comment in isolate_freepages about overlapping |
| * nodes. It is deliberate that the new zone lock is not taken |
| * as memory compaction should not move pages between nodes. |
| */ |
| page = pfn_to_page(low_pfn); |
| if (page_zone(page) != zone) |
| continue; |
| |
| if (!valid_page) |
| valid_page = page; |
| |
| /* If isolation recently failed, do not retry */ |
| pageblock_nr = low_pfn >> pageblock_order; |
| if (!isolation_suitable(cc, page)) |
| goto next_pageblock; |
| |
| /* Skip if free */ |
| if (PageBuddy(page)) |
| continue; |
| |
| /* |
| * For async migration, also only scan in MOVABLE blocks. Async |
| * migration is optimistic to see if the minimum amount of work |
| * satisfies the allocation |
| */ |
| if (!cc->sync && last_pageblock_nr != pageblock_nr && |
| !migrate_async_suitable(get_pageblock_migratetype(page))) { |
| cc->finished_update_migrate = true; |
| goto next_pageblock; |
| } |
| |
| /* |
| * Check may be lockless but that's ok as we recheck later. |
| * It's possible to migrate LRU pages and balloon pages |
| * Skip any other type of page |
| */ |
| if (!PageLRU(page)) { |
| if (unlikely(balloon_page_movable(page))) { |
| if (locked && balloon_page_isolate(page)) { |
| /* Successfully isolated */ |
| cc->finished_update_migrate = true; |
| list_add(&page->lru, migratelist); |
| cc->nr_migratepages++; |
| nr_isolated++; |
| goto check_compact_cluster; |
| } |
| } |
| continue; |
| } |
| |
| /* |
| * PageLRU is set. lru_lock normally excludes isolation |
| * splitting and collapsing (collapsing has already happened |
| * if PageLRU is set) but the lock is not necessarily taken |
| * here and it is wasteful to take it just to check transhuge. |
| * Check TransHuge without lock and skip the whole pageblock if |
| * it's either a transhuge or hugetlbfs page, as calling |
| * compound_order() without preventing THP from splitting the |
| * page underneath us may return surprising results. |
| */ |
| if (PageTransHuge(page)) { |
| if (!locked) |
| goto next_pageblock; |
| low_pfn += (1 << compound_order(page)) - 1; |
| continue; |
| } |
| |
| /* Check if it is ok to still hold the lock */ |
| locked = compact_checklock_irqsave(&zone->lru_lock, &flags, |
| locked, cc); |
| if (!locked || fatal_signal_pending(current)) |
| break; |
| |
| /* Recheck PageLRU and PageTransHuge under lock */ |
| if (!PageLRU(page)) |
| continue; |
| if (PageTransHuge(page)) { |
| low_pfn += (1 << compound_order(page)) - 1; |
| continue; |
| } |
| |
| if (!cc->sync) |
| mode |= ISOLATE_ASYNC_MIGRATE; |
| |
| if (unevictable) |
| mode |= ISOLATE_UNEVICTABLE; |
| |
| lruvec = mem_cgroup_page_lruvec(page, zone); |
| |
| /* Try isolate the page */ |
| if (__isolate_lru_page(page, mode) != 0) |
| continue; |
| |
| VM_BUG_ON(PageTransCompound(page)); |
| |
| /* Successfully isolated */ |
| cc->finished_update_migrate = true; |
| del_page_from_lru_list(page, lruvec, page_lru(page)); |
| list_add(&page->lru, migratelist); |
| cc->nr_migratepages++; |
| nr_isolated++; |
| |
| check_compact_cluster: |
| /* Avoid isolating too much */ |
| if (cc->nr_migratepages == COMPACT_CLUSTER_MAX) { |
| ++low_pfn; |
| break; |
| } |
| |
| continue; |
| |
| next_pageblock: |
| low_pfn = ALIGN(low_pfn + 1, pageblock_nr_pages) - 1; |
| last_pageblock_nr = pageblock_nr; |
| } |
| |
| acct_isolated(zone, locked, cc); |
| |
| if (locked) |
| spin_unlock_irqrestore(&zone->lru_lock, flags); |
| |
| /* Update the pageblock-skip if the whole pageblock was scanned */ |
| if (low_pfn == end_pfn) |
| update_pageblock_skip(cc, valid_page, nr_isolated, true); |
| |
| trace_mm_compaction_isolate_migratepages(nr_scanned, nr_isolated); |
| |
| count_compact_events(COMPACTMIGRATE_SCANNED, nr_scanned); |
| if (nr_isolated) |
| count_compact_events(COMPACTISOLATED, nr_isolated); |
| |
| return low_pfn; |
| } |
| |
| #endif /* CONFIG_COMPACTION || CONFIG_CMA */ |
| #ifdef CONFIG_COMPACTION |
| /* |
| * Based on information in the current compact_control, find blocks |
| * suitable for isolating free pages from and then isolate them. |
| */ |
| static void isolate_freepages(struct zone *zone, |
| struct compact_control *cc) |
| { |
| struct page *page; |
| unsigned long high_pfn, low_pfn, pfn, z_end_pfn; |
| int nr_freepages = cc->nr_freepages; |
| struct list_head *freelist = &cc->freepages; |
| |
| /* |
| * Initialise the free scanner. The starting point is where we last |
| * successfully isolated from, zone-cached value, or the end of the |
| * zone when isolating for the first time. We need this aligned to |
| * the pageblock boundary, because we do pfn -= pageblock_nr_pages |
| * in the for loop. |
| * The low boundary is the end of the pageblock the migration scanner |
| * is using. |
| */ |
| pfn = cc->free_pfn & ~(pageblock_nr_pages-1); |
| low_pfn = ALIGN(cc->migrate_pfn + 1, pageblock_nr_pages); |
| |
| /* |
| * Take care that if the migration scanner is at the end of the zone |
| * that the free scanner does not accidentally move to the next zone |
| * in the next isolation cycle. |
| */ |
| high_pfn = min(low_pfn, pfn); |
| |
| z_end_pfn = zone_end_pfn(zone); |
| |
| /* |
| * Isolate free pages until enough are available to migrate the |
| * pages on cc->migratepages. We stop searching if the migrate |
| * and free page scanners meet or enough free pages are isolated. |
| */ |
| for (; pfn >= low_pfn && cc->nr_migratepages > nr_freepages; |
| pfn -= pageblock_nr_pages) { |
| unsigned long isolated; |
| unsigned long end_pfn; |
| |
| if (!pfn_valid(pfn)) |
| continue; |
| |
| /* |
| * Check for overlapping nodes/zones. It's possible on some |
| * configurations to have a setup like |
| * node0 node1 node0 |
| * i.e. it's possible that all pages within a zones range of |
| * pages do not belong to a single zone. |
| */ |
| page = pfn_to_page(pfn); |
| if (page_zone(page) != zone) |
| continue; |
| |
| /* Check the block is suitable for migration */ |
| if (!suitable_migration_target(page)) |
| continue; |
| |
| /* If isolation recently failed, do not retry */ |
| if (!isolation_suitable(cc, page)) |
| continue; |
| |
| /* Found a block suitable for isolating free pages from */ |
| isolated = 0; |
| |
| /* |
| * Take care when isolating in last pageblock of a zone which |
| * ends in the middle of a pageblock. |
| */ |
| end_pfn = min(pfn + pageblock_nr_pages, z_end_pfn); |
| isolated = isolate_freepages_block(cc, pfn, end_pfn, |
| freelist, false); |
| nr_freepages += isolated; |
| |
| /* |
| * Record the highest PFN we isolated pages from. When next |
| * looking for free pages, the search will restart here as |
| * page migration may have returned some pages to the allocator |
| */ |
| if (isolated) { |
| cc->finished_update_free = true; |
| high_pfn = max(high_pfn, pfn); |
| } |
| } |
| |
| /* split_free_page does not map the pages */ |
| map_pages(freelist); |
| |
| /* |
| * If we crossed the migrate scanner, we want to keep it that way |
| * so that compact_finished() may detect this |
| */ |
| if (pfn < low_pfn) |
| cc->free_pfn = max(pfn, zone->zone_start_pfn); |
| else |
| cc->free_pfn = high_pfn; |
| cc->nr_freepages = nr_freepages; |
| } |
| |
| /* |
| * This is a migrate-callback that "allocates" freepages by taking pages |
| * from the isolated freelists in the block we are migrating to. |
| */ |
| static struct page *compaction_alloc(struct page *migratepage, |
| unsigned long data, |
| int **result) |
| { |
| struct compact_control *cc = (struct compact_control *)data; |
| struct page *freepage; |
| |
| /* Isolate free pages if necessary */ |
| if (list_empty(&cc->freepages)) { |
| isolate_freepages(cc->zone, cc); |
| |
| if (list_empty(&cc->freepages)) |
| return NULL; |
| } |
| |
| freepage = list_entry(cc->freepages.next, struct page, lru); |
| list_del(&freepage->lru); |
| cc->nr_freepages--; |
| |
| return freepage; |
| } |
| |
| /* |
| * We cannot control nr_migratepages and nr_freepages fully when migration is |
| * running as migrate_pages() has no knowledge of compact_control. When |
| * migration is complete, we count the number of pages on the lists by hand. |
| */ |
| static void update_nr_listpages(struct compact_control *cc) |
| { |
| int nr_migratepages = 0; |
| int nr_freepages = 0; |
| struct page *page; |
| |
| list_for_each_entry(page, &cc->migratepages, lru) |
| nr_migratepages++; |
| list_for_each_entry(page, &cc->freepages, lru) |
| nr_freepages++; |
| |
| cc->nr_migratepages = nr_migratepages; |
| cc->nr_freepages = nr_freepages; |
| } |
| |
| /* possible outcome of isolate_migratepages */ |
| typedef enum { |
| ISOLATE_ABORT, /* Abort compaction now */ |
| ISOLATE_NONE, /* No pages isolated, continue scanning */ |
| ISOLATE_SUCCESS, /* Pages isolated, migrate */ |
| } isolate_migrate_t; |
| |
| /* |
| * Isolate all pages that can be migrated from the block pointed to by |
| * the migrate scanner within compact_control. |
| */ |
| static isolate_migrate_t isolate_migratepages(struct zone *zone, |
| struct compact_control *cc) |
| { |
| unsigned long low_pfn, end_pfn; |
| |
| /* Do not scan outside zone boundaries */ |
| low_pfn = max(cc->migrate_pfn, zone->zone_start_pfn); |
| |
| /* Only scan within a pageblock boundary */ |
| end_pfn = ALIGN(low_pfn + 1, pageblock_nr_pages); |
| |
| /* Do not cross the free scanner or scan within a memory hole */ |
| if (end_pfn > cc->free_pfn || !pfn_valid(low_pfn)) { |
| cc->migrate_pfn = end_pfn; |
| return ISOLATE_NONE; |
| } |
| |
| /* Perform the isolation */ |
| low_pfn = isolate_migratepages_range(zone, cc, low_pfn, end_pfn, false); |
| if (!low_pfn || cc->contended) |
| return ISOLATE_ABORT; |
| |
| cc->migrate_pfn = low_pfn; |
| |
| return ISOLATE_SUCCESS; |
| } |
| |
| static int compact_finished(struct zone *zone, |
| struct compact_control *cc) |
| { |
| unsigned int order; |
| unsigned long watermark; |
| |
| if (fatal_signal_pending(current)) |
| return COMPACT_PARTIAL; |
| |
| /* Compaction run completes if the migrate and free scanner meet */ |
| if (cc->free_pfn <= cc->migrate_pfn) { |
| /* |
| * Mark that the PG_migrate_skip information should be cleared |
| * by kswapd when it goes to sleep. kswapd does not set the |
| * flag itself as the decision to be clear should be directly |
| * based on an allocation request. |
| */ |
| if (!current_is_kswapd()) |
| zone->compact_blockskip_flush = true; |
| |
| return COMPACT_COMPLETE; |
| } |
| |
| /* |
| * order == -1 is expected when compacting via |
| * /proc/sys/vm/compact_memory |
| */ |
| if (cc->order == -1) |
| return COMPACT_CONTINUE; |
| |
| /* Compaction run is not finished if the watermark is not met */ |
| watermark = low_wmark_pages(zone); |
| watermark += (1 << cc->order); |
| |
| if (!zone_watermark_ok(zone, cc->order, watermark, 0, 0)) |
| return COMPACT_CONTINUE; |
| |
| /* Direct compactor: Is a suitable page free? */ |
| for (order = cc->order; order < MAX_ORDER; order++) { |
| struct free_area *area = &zone->free_area[order]; |
| |
| /* Job done if page is free of the right migratetype */ |
| if (!list_empty(&area->free_list[cc->migratetype])) |
| return COMPACT_PARTIAL; |
| |
| /* Job done if allocation would set block type */ |
| if (cc->order >= pageblock_order && area->nr_free) |
| return COMPACT_PARTIAL; |
| } |
| |
| return COMPACT_CONTINUE; |
| } |
| |
| /* |
| * compaction_suitable: Is this suitable to run compaction on this zone now? |
| * Returns |
| * COMPACT_SKIPPED - If there are too few free pages for compaction |
| * COMPACT_PARTIAL - If the allocation would succeed without compaction |
| * COMPACT_CONTINUE - If compaction should run now |
| */ |
| unsigned long compaction_suitable(struct zone *zone, int order) |
| { |
| int fragindex; |
| unsigned long watermark; |
| |
| /* |
| * order == -1 is expected when compacting via |
| * /proc/sys/vm/compact_memory |
| */ |
| if (order == -1) |
| return COMPACT_CONTINUE; |
| |
| /* |
| * Watermarks for order-0 must be met for compaction. Note the 2UL. |
| * This is because during migration, copies of pages need to be |
| * allocated and for a short time, the footprint is higher |
| */ |
| watermark = low_wmark_pages(zone) + (2UL << order); |
| if (!zone_watermark_ok(zone, 0, watermark, 0, 0)) |
| return COMPACT_SKIPPED; |
| |
| /* |
| * fragmentation index determines if allocation failures are due to |
| * low memory or external fragmentation |
| * |
| * index of -1000 implies allocations might succeed depending on |
| * watermarks |
| * 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. |
| */ |
| fragindex = fragmentation_index(zone, order); |
| if (fragindex >= 0 && fragindex <= sysctl_extfrag_threshold) |
| return COMPACT_SKIPPED; |
| |
| if (fragindex == -1000 && zone_watermark_ok(zone, order, watermark, |
| 0, 0)) |
| return COMPACT_PARTIAL; |
| |
| return COMPACT_CONTINUE; |
| } |
| |
| static int compact_zone(struct zone *zone, struct compact_control *cc) |
| { |
| int ret; |
| unsigned long start_pfn = zone->zone_start_pfn; |
| unsigned long end_pfn = zone_end_pfn(zone); |
| |
| ret = compaction_suitable(zone, cc->order); |
| switch (ret) { |
| case COMPACT_PARTIAL: |
| case COMPACT_SKIPPED: |
| /* Compaction is likely to fail */ |
| return ret; |
| case COMPACT_CONTINUE: |
| /* Fall through to compaction */ |
| ; |
| } |
| |
| /* |
| * Clear pageblock skip if there were failures recently and compaction |
| * is about to be retried after being deferred. kswapd does not do |
| * this reset as it'll reset the cached information when going to sleep. |
| */ |
| if (compaction_restarting(zone, cc->order) && !current_is_kswapd()) |
| __reset_isolation_suitable(zone); |
| |
| /* |
| * Setup to move all movable pages to the end of the zone. Used cached |
| * information on where the scanners should start but check that it |
| * is initialised by ensuring the values are within zone boundaries. |
| */ |
| cc->migrate_pfn = zone->compact_cached_migrate_pfn; |
| cc->free_pfn = zone->compact_cached_free_pfn; |
| if (cc->free_pfn < start_pfn || cc->free_pfn > end_pfn) { |
| cc->free_pfn = end_pfn & ~(pageblock_nr_pages-1); |
| zone->compact_cached_free_pfn = cc->free_pfn; |
| } |
| if (cc->migrate_pfn < start_pfn || cc->migrate_pfn > end_pfn) { |
| cc->migrate_pfn = start_pfn; |
| zone->compact_cached_migrate_pfn = cc->migrate_pfn; |
| } |
| |
| migrate_prep_local(); |
| |
| while ((ret = compact_finished(zone, cc)) == COMPACT_CONTINUE) { |
| unsigned long nr_migrate, nr_remaining; |
| int err; |
| |
| switch (isolate_migratepages(zone, cc)) { |
| case ISOLATE_ABORT: |
| ret = COMPACT_PARTIAL; |
| putback_movable_pages(&cc->migratepages); |
| cc->nr_migratepages = 0; |
| goto out; |
| case ISOLATE_NONE: |
| continue; |
| case ISOLATE_SUCCESS: |
| ; |
| } |
| |
| nr_migrate = cc->nr_migratepages; |
| err = migrate_pages(&cc->migratepages, compaction_alloc, |
| (unsigned long)cc, |
| cc->sync ? MIGRATE_SYNC_LIGHT : MIGRATE_ASYNC, |
| MR_COMPACTION); |
| update_nr_listpages(cc); |
| nr_remaining = cc->nr_migratepages; |
| |
| trace_mm_compaction_migratepages(nr_migrate - nr_remaining, |
| nr_remaining); |
| |
| /* Release isolated pages not migrated */ |
| if (err) { |
| putback_movable_pages(&cc->migratepages); |
| cc->nr_migratepages = 0; |
| /* |
| * migrate_pages() may return -ENOMEM when scanners meet |
| * and we want compact_finished() to detect it |
| */ |
| if (err == -ENOMEM && cc->free_pfn > cc->migrate_pfn) { |
| ret = COMPACT_PARTIAL; |
| goto out; |
| } |
| } |
| } |
| |
| out: |
| /* Release free pages and check accounting */ |
| cc->nr_freepages -= release_freepages(&cc->freepages); |
| VM_BUG_ON(cc->nr_freepages != 0); |
| |
| return ret; |
| } |
| |
| static unsigned long compact_zone_order(struct zone *zone, |
| int order, gfp_t gfp_mask, |
| bool sync, bool *contended) |
| { |
| unsigned long ret; |
| struct compact_control cc = { |
| .nr_freepages = 0, |
| .nr_migratepages = 0, |
| .order = order, |
| .migratetype = allocflags_to_migratetype(gfp_mask), |
| .zone = zone, |
| .sync = sync, |
| }; |
| INIT_LIST_HEAD(&cc.freepages); |
| INIT_LIST_HEAD(&cc.migratepages); |
| |
| ret = compact_zone(zone, &cc); |
| |
| VM_BUG_ON(!list_empty(&cc.freepages)); |
| VM_BUG_ON(!list_empty(&cc.migratepages)); |
| |
| *contended = cc.contended; |
| return ret; |
| } |
| |
| int sysctl_extfrag_threshold = 500; |
| |
| /** |
| * try_to_compact_pages - Direct compact to satisfy a high-order allocation |
| * @zonelist: The zonelist used for the current allocation |
| * @order: The order of the current allocation |
| * @gfp_mask: The GFP mask of the current allocation |
| * @nodemask: The allowed nodes to allocate from |
| * @sync: Whether migration is synchronous or not |
| * @contended: Return value that is true if compaction was aborted due to lock contention |
| * @page: Optionally capture a free page of the requested order during compaction |
| * |
| * This is the main entry point for direct page compaction. |
| */ |
| unsigned long try_to_compact_pages(struct zonelist *zonelist, |
| int order, gfp_t gfp_mask, nodemask_t *nodemask, |
| bool sync, bool *contended) |
| { |
| enum zone_type high_zoneidx = gfp_zone(gfp_mask); |
| int may_enter_fs = gfp_mask & __GFP_FS; |
| int may_perform_io = gfp_mask & __GFP_IO; |
| struct zoneref *z; |
| struct zone *zone; |
| int rc = COMPACT_SKIPPED; |
| int alloc_flags = 0; |
| |
| /* Check if the GFP flags allow compaction */ |
| if (!order || !may_enter_fs || !may_perform_io) |
| return rc; |
| |
| count_compact_event(COMPACTSTALL); |
| |
| #ifdef CONFIG_CMA |
| if (allocflags_to_migratetype(gfp_mask) == MIGRATE_MOVABLE) |
| alloc_flags |= ALLOC_CMA; |
| #endif |
| /* Compact each zone in the list */ |
| for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx, |
| nodemask) { |
| int status; |
| |
| status = compact_zone_order(zone, order, gfp_mask, sync, |
| contended); |
| rc = max(status, rc); |
| |
| /* If a normal allocation would succeed, stop compacting */ |
| if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, |
| alloc_flags)) |
| break; |
| } |
| |
| return rc; |
| } |
| |
| |
| /* Compact all zones within a node */ |
| static void __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc) |
| { |
| int zoneid; |
| struct zone *zone; |
| |
| for (zoneid = 0; zoneid < MAX_NR_ZONES; zoneid++) { |
| |
| zone = &pgdat->node_zones[zoneid]; |
| if (!populated_zone(zone)) |
| continue; |
| |
| cc->nr_freepages = 0; |
| cc->nr_migratepages = 0; |
| cc->zone = zone; |
| INIT_LIST_HEAD(&cc->freepages); |
| INIT_LIST_HEAD(&cc->migratepages); |
| |
| if (cc->order == -1 || !compaction_deferred(zone, cc->order)) |
| compact_zone(zone, cc); |
| |
| if (cc->order > 0) { |
| int ok = zone_watermark_ok(zone, cc->order, |
| low_wmark_pages(zone), 0, 0); |
| if (ok && cc->order >= zone->compact_order_failed) |
| zone->compact_order_failed = cc->order + 1; |
| /* Currently async compaction is never deferred. */ |
| else if (!ok && cc->sync) |
| defer_compaction(zone, cc->order); |
| } |
| |
| VM_BUG_ON(!list_empty(&cc->freepages)); |
| VM_BUG_ON(!list_empty(&cc->migratepages)); |
| } |
| } |
| |
| void compact_pgdat(pg_data_t *pgdat, int order) |
| { |
| struct compact_control cc = { |
| .order = order, |
| .sync = false, |
| }; |
| |
| __compact_pgdat(pgdat, &cc); |
| } |
| |
| static void compact_node(int nid) |
| { |
| struct compact_control cc = { |
| .order = -1, |
| .sync = true, |
| }; |
| |
| __compact_pgdat(NODE_DATA(nid), &cc); |
| } |
| |
| /* Compact all nodes in the system */ |
| static void compact_nodes(void) |
| { |
| int nid; |
| |
| /* Flush pending updates to the LRU lists */ |
| lru_add_drain_all(); |
| |
| for_each_online_node(nid) |
| compact_node(nid); |
| } |
| |
| /* The written value is actually unused, all memory is compacted */ |
| int sysctl_compact_memory; |
| |
| /* This is the entry point for compacting all nodes via /proc/sys/vm */ |
| int sysctl_compaction_handler(struct ctl_table *table, int write, |
| void __user *buffer, size_t *length, loff_t *ppos) |
| { |
| if (write) |
| compact_nodes(); |
| |
| return 0; |
| } |
| |
| int sysctl_extfrag_handler(struct ctl_table *table, int write, |
| void __user *buffer, size_t *length, loff_t *ppos) |
| { |
| proc_dointvec_minmax(table, write, buffer, length, ppos); |
| |
| return 0; |
| } |
| |
| #if defined(CONFIG_SYSFS) && defined(CONFIG_NUMA) |
| ssize_t sysfs_compact_node(struct device *dev, |
| struct device_attribute *attr, |
| const char *buf, size_t count) |
| { |
| int nid = dev->id; |
| |
| if (nid >= 0 && nid < nr_node_ids && node_online(nid)) { |
| /* Flush pending updates to the LRU lists */ |
| lru_add_drain_all(); |
| |
| compact_node(nid); |
| } |
| |
| return count; |
| } |
| static DEVICE_ATTR(compact, S_IWUSR, NULL, sysfs_compact_node); |
| |
| int compaction_register_node(struct node *node) |
| { |
| return device_create_file(&node->dev, &dev_attr_compact); |
| } |
| |
| void compaction_unregister_node(struct node *node) |
| { |
| return device_remove_file(&node->dev, &dev_attr_compact); |
| } |
| #endif /* CONFIG_SYSFS && CONFIG_NUMA */ |
| |
| #endif /* CONFIG_COMPACTION */ |