/* * linux/mm/swap.c * * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds */ /* * This file contains the default values for the opereation 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/module.h> #include <linux/percpu_counter.h> #include <linux/percpu.h> #include <linux/cpu.h> #include <linux/notifier.h> #include <linux/init.h> /* How many pages do we try to swap or page in/out together? */ int page_cluster; void put_page(struct page *page) { if (unlikely(PageCompound(page))) { page = (struct page *)page_private(page); if (put_page_testzero(page)) { void (*dtor)(struct page *page); dtor = (void (*)(struct page *))page[1].mapping; (*dtor)(page); } return; } if (put_page_testzero(page)) __page_cache_release(page); } EXPORT_SYMBOL(put_page); /* * 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. The page still has PageWriteback set, which will pin it. * * We don't expect many pages to come through here, so don't bother batching * things up. * * To avoid placing the page at the tail of the LRU while PG_writeback is still * set, this function will clear PG_writeback before performing the page * motion. Do that inside the lru lock because once PG_writeback is cleared * we may not touch the page. * * Returns zero if it cleared PG_writeback. */ int rotate_reclaimable_page(struct page *page) { struct zone *zone; unsigned long flags; if (PageLocked(page)) return 1; if (PageDirty(page)) return 1; if (PageActive(page)) return 1; if (!PageLRU(page)) return 1; zone = page_zone(page); spin_lock_irqsave(&zone->lru_lock, flags); if (PageLRU(page) && !PageActive(page)) { list_del(&page->lru); list_add_tail(&page->lru, &zone->inactive_list); inc_page_state(pgrotated); } if (!test_clear_page_writeback(page)) BUG(); spin_unlock_irqrestore(&zone->lru_lock, flags); return 0; } /* * FIXME: speed this up? */ void fastcall activate_page(struct page *page) { struct zone *zone = page_zone(page); spin_lock_irq(&zone->lru_lock); if (PageLRU(page) && !PageActive(page)) { del_page_from_inactive_list(zone, page); SetPageActive(page); add_page_to_active_list(zone, page); inc_page_state(pgactivate); } 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 fastcall mark_page_accessed(struct page *page) { if (!PageActive(page) && PageReferenced(page) && PageLRU(page)) { activate_page(page); ClearPageReferenced(page); } else if (!PageReferenced(page)) { SetPageReferenced(page); } } EXPORT_SYMBOL(mark_page_accessed); /** * lru_cache_add: add a page to the page lists * @page: the page to add */ static DEFINE_PER_CPU(struct pagevec, lru_add_pvecs) = { 0, }; static DEFINE_PER_CPU(struct pagevec, lru_add_active_pvecs) = { 0, }; void fastcall lru_cache_add(struct page *page) { struct pagevec *pvec = &get_cpu_var(lru_add_pvecs); page_cache_get(page); if (!pagevec_add(pvec, page)) __pagevec_lru_add(pvec); put_cpu_var(lru_add_pvecs); } void fastcall lru_cache_add_active(struct page *page) { struct pagevec *pvec = &get_cpu_var(lru_add_active_pvecs); page_cache_get(page); if (!pagevec_add(pvec, page)) __pagevec_lru_add_active(pvec); put_cpu_var(lru_add_active_pvecs); } static void __lru_add_drain(int cpu) { struct pagevec *pvec = &per_cpu(lru_add_pvecs, cpu); /* CPU is dead, so no locking needed. */ if (pagevec_count(pvec)) __pagevec_lru_add(pvec); pvec = &per_cpu(lru_add_active_pvecs, cpu); if (pagevec_count(pvec)) __pagevec_lru_add_active(pvec); } void lru_add_drain(void) { __lru_add_drain(get_cpu()); put_cpu(); } /* * This path almost never happens for VM activity - pages are normally * freed via pagevecs. But it gets used by networking. */ void fastcall __page_cache_release(struct page *page) { unsigned long flags; struct zone *zone = page_zone(page); spin_lock_irqsave(&zone->lru_lock, flags); if (TestClearPageLRU(page)) del_page_from_lru(zone, page); if (page_count(page) != 0) page = NULL; spin_unlock_irqrestore(&zone->lru_lock, flags); if (page) free_hot_page(page); } EXPORT_SYMBOL(__page_cache_release); /* * 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_cache(): we recheck the * page count inside the lock to see whether shrink_cache grabbed the page * via the LRU. If it did, give up: shrink_cache will free it. */ void release_pages(struct page **pages, int nr, int cold) { int i; struct pagevec pages_to_free; struct zone *zone = NULL; pagevec_init(&pages_to_free, cold); for (i = 0; i < nr; i++) { struct page *page = pages[i]; struct zone *pagezone; if (!put_page_testzero(page)) continue; pagezone = page_zone(page); if (pagezone != zone) { if (zone) spin_unlock_irq(&zone->lru_lock); zone = pagezone; spin_lock_irq(&zone->lru_lock); } if (TestClearPageLRU(page)) del_page_from_lru(zone, page); if (page_count(page) == 0) { if (!pagevec_add(&pages_to_free, page)) { spin_unlock_irq(&zone->lru_lock); __pagevec_free(&pages_to_free); pagevec_reinit(&pages_to_free); zone = NULL; /* No lock is held */ } } } if (zone) spin_unlock_irq(&zone->lru_lock); 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); /* * pagevec_release() for pages which are known to not be on the LRU * * This function reinitialises the caller's pagevec. */ void __pagevec_release_nonlru(struct pagevec *pvec) { int i; struct pagevec pages_to_free; pagevec_init(&pages_to_free, pvec->cold); for (i = 0; i < pagevec_count(pvec); i++) { struct page *page = pvec->pages[i]; BUG_ON(PageLRU(page)); if (put_page_testzero(page)) pagevec_add(&pages_to_free, page); } pagevec_free(&pages_to_free); pagevec_reinit(pvec); } /* * 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) { int i; 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_irq(&zone->lru_lock); zone = pagezone; spin_lock_irq(&zone->lru_lock); } if (TestSetPageLRU(page)) BUG(); add_page_to_inactive_list(zone, page); } if (zone) spin_unlock_irq(&zone->lru_lock); release_pages(pvec->pages, pvec->nr, pvec->cold); pagevec_reinit(pvec); } EXPORT_SYMBOL(__pagevec_lru_add); void __pagevec_lru_add_active(struct pagevec *pvec) { int i; 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_irq(&zone->lru_lock); zone = pagezone; spin_lock_irq(&zone->lru_lock); } if (TestSetPageLRU(page)) BUG(); if (TestSetPageActive(page)) BUG(); add_page_to_active_list(zone, page); } if (zone) spin_unlock_irq(&zone->lru_lock); release_pages(pvec->pages, pvec->nr, pvec->cold); pagevec_reinit(pvec); } /* * 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) && !TestSetPageLocked(page)) { try_to_release_page(page, 0); 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); } 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) = 0; 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_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) { atomic_add(*committed, &vm_committed_space); *committed = 0; __lru_add_drain((long)hcpu); } return NOTIFY_OK; } #endif /* CONFIG_HOTPLUG_CPU */ #endif /* CONFIG_SMP */ #ifdef CONFIG_SMP void percpu_counter_mod(struct percpu_counter *fbc, long amount) { long count; long *pcount; int cpu = get_cpu(); pcount = per_cpu_ptr(fbc->counters, cpu); count = *pcount + amount; if (count >= FBC_BATCH || count <= -FBC_BATCH) { spin_lock(&fbc->lock); fbc->count += count; spin_unlock(&fbc->lock); count = 0; } *pcount = count; put_cpu(); } EXPORT_SYMBOL(percpu_counter_mod); #endif /* * Perform any setup for the swap system */ void __init swap_setup(void) { unsigned long megs = num_physpages >> (20 - PAGE_SHIFT); /* 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 */ hotcpu_notifier(cpu_swap_callback, 0); }