/* * linux/mm/swap.c * * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds */ /* * This file contains the default values for the operation of the * Linux VM subsystem. Fine-tuning documentation can be found in * Documentation/sysctl/vm.txt. * Started 18.12.91 * Swap aging added 23.2.95, Stephen Tweedie. * Buffermem limits added 12.3.98, Rik van Riel. */ #include <linux/mm.h> #include <linux/sched.h> #include <linux/kernel_stat.h> #include <linux/swap.h> #include <linux/mman.h> #include <linux/pagemap.h> #include <linux/pagevec.h> #include <linux/init.h> #include <linux/module.h> #include <linux/mm_inline.h> #include <linux/buffer_head.h> /* for try_to_release_page() */ #include <linux/percpu_counter.h> #include <linux/percpu.h> #include <linux/cpu.h> #include <linux/notifier.h> #include <linux/backing-dev.h> #include <linux/memcontrol.h> #include "internal.h" /* How many pages do we try to swap or page in/out together? */ int page_cluster; static DEFINE_PER_CPU(struct pagevec[NR_LRU_LISTS], lru_add_pvecs); static DEFINE_PER_CPU(struct pagevec, lru_rotate_pvecs); /* * This path almost never happens for VM activity - pages are normally * freed via pagevecs. But it gets used by networking. */ static void __page_cache_release(struct page *page) { if (PageLRU(page)) { unsigned long flags; struct zone *zone = page_zone(page); spin_lock_irqsave(&zone->lru_lock, flags); VM_BUG_ON(!PageLRU(page)); __ClearPageLRU(page); del_page_from_lru(zone, page); spin_unlock_irqrestore(&zone->lru_lock, flags); } free_hot_page(page); } static void put_compound_page(struct page *page) { page = compound_head(page); if (put_page_testzero(page)) { compound_page_dtor *dtor; dtor = get_compound_page_dtor(page); (*dtor)(page); } } void put_page(struct page *page) { if (unlikely(PageCompound(page))) put_compound_page(page); else if (put_page_testzero(page)) __page_cache_release(page); } EXPORT_SYMBOL(put_page); /** * put_pages_list() - release a list of pages * @pages: list of pages threaded on page->lru * * Release a list of pages which are strung together on page.lru. Currently * used by read_cache_pages() and related error recovery code. */ void put_pages_list(struct list_head *pages) { while (!list_empty(pages)) { struct page *victim; victim = list_entry(pages->prev, struct page, lru); list_del(&victim->lru); page_cache_release(victim); } } EXPORT_SYMBOL(put_pages_list); /* * pagevec_move_tail() must be called with IRQ disabled. * Otherwise this may cause nasty races. */ static void pagevec_move_tail(struct pagevec *pvec) { int i; int pgmoved = 0; struct zone *zone = NULL; for (i = 0; i < pagevec_count(pvec); i++) { struct page *page = pvec->pages[i]; struct zone *pagezone = page_zone(page); if (pagezone != zone) { if (zone) spin_unlock(&zone->lru_lock); zone = pagezone; spin_lock(&zone->lru_lock); } if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) { int lru = page_is_file_cache(page); list_move_tail(&page->lru, &zone->lru[lru].list); pgmoved++; } } if (zone) spin_unlock(&zone->lru_lock); __count_vm_events(PGROTATED, pgmoved); release_pages(pvec->pages, pvec->nr, pvec->cold); pagevec_reinit(pvec); } /* * Writeback is about to end against a page which has been marked for immediate * reclaim. If it still appears to be reclaimable, move it to the tail of the * inactive list. */ void rotate_reclaimable_page(struct page *page) { if (!PageLocked(page) && !PageDirty(page) && !PageActive(page) && !PageUnevictable(page) && PageLRU(page)) { struct pagevec *pvec; unsigned long flags; page_cache_get(page); local_irq_save(flags); pvec = &__get_cpu_var(lru_rotate_pvecs); if (!pagevec_add(pvec, page)) pagevec_move_tail(pvec); local_irq_restore(flags); } } static void update_page_reclaim_stat(struct zone *zone, struct page *page, int file, int rotated) { struct zone_reclaim_stat *reclaim_stat = &zone->reclaim_stat; struct zone_reclaim_stat *memcg_reclaim_stat; memcg_reclaim_stat = mem_cgroup_get_reclaim_stat_from_page(page); reclaim_stat->recent_scanned[file]++; if (rotated) reclaim_stat->recent_rotated[file]++; if (!memcg_reclaim_stat) return; memcg_reclaim_stat->recent_scanned[file]++; if (rotated) memcg_reclaim_stat->recent_rotated[file]++; } /* * FIXME: speed this up? */ void activate_page(struct page *page) { struct zone *zone = page_zone(page); spin_lock_irq(&zone->lru_lock); if (PageLRU(page) && !PageActive(page) && !PageUnevictable(page)) { int file = page_is_file_cache(page); int lru = LRU_BASE + file; del_page_from_lru_list(zone, page, lru); SetPageActive(page); lru += LRU_ACTIVE; add_page_to_lru_list(zone, page, lru); __count_vm_event(PGACTIVATE); update_page_reclaim_stat(zone, page, !!file, 1); } spin_unlock_irq(&zone->lru_lock); } /* * Mark a page as having seen activity. * * inactive,unreferenced -> inactive,referenced * inactive,referenced -> active,unreferenced * active,unreferenced -> active,referenced */ void mark_page_accessed(struct page *page) { if (!PageActive(page) && !PageUnevictable(page) && PageReferenced(page) && PageLRU(page)) { activate_page(page); ClearPageReferenced(page); } else if (!PageReferenced(page)) { SetPageReferenced(page); } } EXPORT_SYMBOL(mark_page_accessed); void __lru_cache_add(struct page *page, enum lru_list lru) { struct pagevec *pvec = &get_cpu_var(lru_add_pvecs)[lru]; page_cache_get(page); if (!pagevec_add(pvec, page)) ____pagevec_lru_add(pvec, lru); put_cpu_var(lru_add_pvecs); } /** * lru_cache_add_lru - add a page to a page list * @page: the page to be added to the LRU. * @lru: the LRU list to which the page is added. */ void lru_cache_add_lru(struct page *page, enum lru_list lru) { if (PageActive(page)) { VM_BUG_ON(PageUnevictable(page)); ClearPageActive(page); } else if (PageUnevictable(page)) { VM_BUG_ON(PageActive(page)); ClearPageUnevictable(page); } VM_BUG_ON(PageLRU(page) || PageActive(page) || PageUnevictable(page)); __lru_cache_add(page, lru); } /** * add_page_to_unevictable_list - add a page to the unevictable list * @page: the page to be added to the unevictable list * * Add page directly to its zone's unevictable list. To avoid races with * tasks that might be making the page evictable, through eg. munlock, * munmap or exit, while it's not on the lru, we want to add the page * while it's locked or otherwise "invisible" to other tasks. This is * difficult to do when using the pagevec cache, so bypass that. */ void add_page_to_unevictable_list(struct page *page) { struct zone *zone = page_zone(page); spin_lock_irq(&zone->lru_lock); SetPageUnevictable(page); SetPageLRU(page); add_page_to_lru_list(zone, page, LRU_UNEVICTABLE); spin_unlock_irq(&zone->lru_lock); } /* * Drain pages out of the cpu's pagevecs. * Either "cpu" is the current CPU, and preemption has already been * disabled; or "cpu" is being hot-unplugged, and is already dead. */ static void drain_cpu_pagevecs(int cpu) { struct pagevec *pvecs = per_cpu(lru_add_pvecs, cpu); struct pagevec *pvec; int lru; for_each_lru(lru) { pvec = &pvecs[lru - LRU_BASE]; if (pagevec_count(pvec)) ____pagevec_lru_add(pvec, lru); } pvec = &per_cpu(lru_rotate_pvecs, cpu); if (pagevec_count(pvec)) { unsigned long flags; /* No harm done if a racing interrupt already did this */ local_irq_save(flags); pagevec_move_tail(pvec); local_irq_restore(flags); } } void lru_add_drain(void) { drain_cpu_pagevecs(get_cpu()); put_cpu(); } static void lru_add_drain_per_cpu(struct work_struct *dummy) { lru_add_drain(); } /* * Returns 0 for success */ int lru_add_drain_all(void) { return schedule_on_each_cpu(lru_add_drain_per_cpu); } /* * Batched page_cache_release(). Decrement the reference count on all the * passed pages. If it fell to zero then remove the page from the LRU and * free it. * * Avoid taking zone->lru_lock if possible, but if it is taken, retain it * for the remainder of the operation. * * The locking in this function is against shrink_inactive_list(): we recheck * the page count inside the lock to see whether shrink_inactive_list() * grabbed the page via the LRU. If it did, give up: shrink_inactive_list() * will free it. */ void release_pages(struct page **pages, int nr, int cold) { int i; struct pagevec pages_to_free; struct zone *zone = NULL; unsigned long uninitialized_var(flags); pagevec_init(&pages_to_free, cold); for (i = 0; i < nr; i++) { struct page *page = pages[i]; if (unlikely(PageCompound(page))) { if (zone) { spin_unlock_irqrestore(&zone->lru_lock, flags); zone = NULL; } put_compound_page(page); continue; } if (!put_page_testzero(page)) continue; if (PageLRU(page)) { struct zone *pagezone = page_zone(page); if (pagezone != zone) { if (zone) spin_unlock_irqrestore(&zone->lru_lock, flags); zone = pagezone; spin_lock_irqsave(&zone->lru_lock, flags); } VM_BUG_ON(!PageLRU(page)); __ClearPageLRU(page); del_page_from_lru(zone, page); } if (!pagevec_add(&pages_to_free, page)) { if (zone) { spin_unlock_irqrestore(&zone->lru_lock, flags); zone = NULL; } __pagevec_free(&pages_to_free); pagevec_reinit(&pages_to_free); } } if (zone) spin_unlock_irqrestore(&zone->lru_lock, flags); pagevec_free(&pages_to_free); } /* * The pages which we're about to release may be in the deferred lru-addition * queues. That would prevent them from really being freed right now. That's * OK from a correctness point of view but is inefficient - those pages may be * cache-warm and we want to give them back to the page allocator ASAP. * * So __pagevec_release() will drain those queues here. __pagevec_lru_add() * and __pagevec_lru_add_active() call release_pages() directly to avoid * mutual recursion. */ void __pagevec_release(struct pagevec *pvec) { lru_add_drain(); release_pages(pvec->pages, pagevec_count(pvec), pvec->cold); pagevec_reinit(pvec); } EXPORT_SYMBOL(__pagevec_release); /* * Add the passed pages to the LRU, then drop the caller's refcount * on them. Reinitialises the caller's pagevec. */ void ____pagevec_lru_add(struct pagevec *pvec, enum lru_list lru) { int i; struct zone *zone = NULL; VM_BUG_ON(is_unevictable_lru(lru)); for (i = 0; i < pagevec_count(pvec); i++) { struct page *page = pvec->pages[i]; struct zone *pagezone = page_zone(page); int file; int active; if (pagezone != zone) { if (zone) spin_unlock_irq(&zone->lru_lock); zone = pagezone; spin_lock_irq(&zone->lru_lock); } VM_BUG_ON(PageActive(page)); VM_BUG_ON(PageUnevictable(page)); VM_BUG_ON(PageLRU(page)); SetPageLRU(page); active = is_active_lru(lru); file = is_file_lru(lru); if (active) SetPageActive(page); update_page_reclaim_stat(zone, page, file, active); add_page_to_lru_list(zone, page, lru); } if (zone) spin_unlock_irq(&zone->lru_lock); release_pages(pvec->pages, pvec->nr, pvec->cold); pagevec_reinit(pvec); } EXPORT_SYMBOL(____pagevec_lru_add); /* * Try to drop buffers from the pages in a pagevec */ void pagevec_strip(struct pagevec *pvec) { int i; for (i = 0; i < pagevec_count(pvec); i++) { struct page *page = pvec->pages[i]; if (PagePrivate(page) && trylock_page(page)) { if (PagePrivate(page)) try_to_release_page(page, 0); unlock_page(page); } } } /** * pagevec_swap_free - try to free swap space from the pages in a pagevec * @pvec: pagevec with swapcache pages to free the swap space of * * The caller needs to hold an extra reference to each page and * not hold the page lock on the pages. This function uses a * trylock on the page lock so it may not always free the swap * space associated with a page. */ void pagevec_swap_free(struct pagevec *pvec) { int i; for (i = 0; i < pagevec_count(pvec); i++) { struct page *page = pvec->pages[i]; if (PageSwapCache(page) && trylock_page(page)) { try_to_free_swap(page); unlock_page(page); } } } /** * pagevec_lookup - gang pagecache lookup * @pvec: Where the resulting pages are placed * @mapping: The address_space to search * @start: The starting page index * @nr_pages: The maximum number of pages * * pagevec_lookup() will search for and return a group of up to @nr_pages pages * in the mapping. The pages are placed in @pvec. pagevec_lookup() takes a * reference against the pages in @pvec. * * The search returns a group of mapping-contiguous pages with ascending * indexes. There may be holes in the indices due to not-present pages. * * pagevec_lookup() returns the number of pages which were found. */ unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping, pgoff_t start, unsigned nr_pages) { pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages); return pagevec_count(pvec); } EXPORT_SYMBOL(pagevec_lookup); unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping, pgoff_t *index, int tag, unsigned nr_pages) { pvec->nr = find_get_pages_tag(mapping, index, tag, nr_pages, pvec->pages); return pagevec_count(pvec); } EXPORT_SYMBOL(pagevec_lookup_tag); #ifdef CONFIG_SMP /* * We tolerate a little inaccuracy to avoid ping-ponging the counter between * CPUs */ #define ACCT_THRESHOLD max(16, NR_CPUS * 2) static DEFINE_PER_CPU(long, committed_space); void vm_acct_memory(long pages) { long *local; preempt_disable(); local = &__get_cpu_var(committed_space); *local += pages; if (*local > ACCT_THRESHOLD || *local < -ACCT_THRESHOLD) { atomic_long_add(*local, &vm_committed_space); *local = 0; } preempt_enable(); } #ifdef CONFIG_HOTPLUG_CPU /* Drop the CPU's cached committed space back into the central pool. */ static int cpu_swap_callback(struct notifier_block *nfb, unsigned long action, void *hcpu) { long *committed; committed = &per_cpu(committed_space, (long)hcpu); if (action == CPU_DEAD || action == CPU_DEAD_FROZEN) { atomic_long_add(*committed, &vm_committed_space); *committed = 0; drain_cpu_pagevecs((long)hcpu); } return NOTIFY_OK; } #endif /* CONFIG_HOTPLUG_CPU */ #endif /* CONFIG_SMP */ /* * Perform any setup for the swap system */ void __init swap_setup(void) { unsigned long megs = num_physpages >> (20 - PAGE_SHIFT); #ifdef CONFIG_SWAP bdi_init(swapper_space.backing_dev_info); #endif /* Use a smaller cluster for small-memory machines */ if (megs < 16) page_cluster = 2; else page_cluster = 3; /* * Right now other parts of the system means that we * _really_ don't want to cluster much more */ #ifdef CONFIG_HOTPLUG_CPU hotcpu_notifier(cpu_swap_callback, 0); #endif }