diff options
Diffstat (limited to 'mm/vmscan.c')
| -rw-r--r-- | mm/vmscan.c | 3439 |
1 files changed, 3439 insertions, 0 deletions
diff --git a/mm/vmscan.c b/mm/vmscan.c new file mode 100644 index 00000000..769935d1 --- /dev/null +++ b/mm/vmscan.c @@ -0,0 +1,3439 @@ +/* + * linux/mm/vmscan.c + * + * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds + * + * Swap reorganised 29.12.95, Stephen Tweedie. + * kswapd added: 7.1.96 sct + * Removed kswapd_ctl limits, and swap out as many pages as needed + * to bring the system back to freepages.high: 2.4.97, Rik van Riel. + * Zone aware kswapd started 02/00, Kanoj Sarcar (kanoj@sgi.com). + * Multiqueue VM started 5.8.00, Rik van Riel. + */ + +#include <linux/mm.h> +#include <linux/module.h> +#include <linux/gfp.h> +#include <linux/kernel_stat.h> +#include <linux/swap.h> +#include <linux/pagemap.h> +#include <linux/init.h> +#include <linux/highmem.h> +#include <linux/vmstat.h> +#include <linux/file.h> +#include <linux/writeback.h> +#include <linux/blkdev.h> +#include <linux/buffer_head.h> /* for try_to_release_page(), + buffer_heads_over_limit */ +#include <linux/mm_inline.h> +#include <linux/pagevec.h> +#include <linux/backing-dev.h> +#include <linux/rmap.h> +#include <linux/topology.h> +#include <linux/cpu.h> +#include <linux/cpuset.h> +#include <linux/compaction.h> +#include <linux/notifier.h> +#include <linux/rwsem.h> +#include <linux/delay.h> +#include <linux/kthread.h> +#include <linux/freezer.h> +#include <linux/memcontrol.h> +#include <linux/delayacct.h> +#include <linux/sysctl.h> +#include <linux/oom.h> +#include <linux/prefetch.h> + +#include <asm/tlbflush.h> +#include <asm/div64.h> + +#include <linux/swapops.h> + +#include "internal.h" + +#define CREATE_TRACE_POINTS +#include <trace/events/vmscan.h> + +/* + * reclaim_mode determines how the inactive list is shrunk + * RECLAIM_MODE_SINGLE: Reclaim only order-0 pages + * RECLAIM_MODE_ASYNC: Do not block + * RECLAIM_MODE_SYNC: Allow blocking e.g. call wait_on_page_writeback + * RECLAIM_MODE_LUMPYRECLAIM: For high-order allocations, take a reference + * page from the LRU and reclaim all pages within a + * naturally aligned range + * RECLAIM_MODE_COMPACTION: For high-order allocations, reclaim a number of + * order-0 pages and then compact the zone + */ +typedef unsigned __bitwise__ reclaim_mode_t; +#define RECLAIM_MODE_SINGLE ((__force reclaim_mode_t)0x01u) +#define RECLAIM_MODE_ASYNC ((__force reclaim_mode_t)0x02u) +#define RECLAIM_MODE_SYNC ((__force reclaim_mode_t)0x04u) +#define RECLAIM_MODE_LUMPYRECLAIM ((__force reclaim_mode_t)0x08u) +#define RECLAIM_MODE_COMPACTION ((__force reclaim_mode_t)0x10u) + +struct scan_control { + /* Incremented by the number of inactive pages that were scanned */ + unsigned long nr_scanned; + + /* Number of pages freed so far during a call to shrink_zones() */ + unsigned long nr_reclaimed; + + /* How many pages shrink_list() should reclaim */ + unsigned long nr_to_reclaim; + + unsigned long hibernation_mode; + + /* This context's GFP mask */ + gfp_t gfp_mask; + + int may_writepage; + + /* Can mapped pages be reclaimed? */ + int may_unmap; + + /* Can pages be swapped as part of reclaim? */ + int may_swap; + + int swappiness; + + int order; + + /* + * Intend to reclaim enough continuous memory rather than reclaim + * enough amount of memory. i.e, mode for high order allocation. + */ + reclaim_mode_t reclaim_mode; + + /* Which cgroup do we reclaim from */ + struct mem_cgroup *mem_cgroup; + + /* + * Nodemask of nodes allowed by the caller. If NULL, all nodes + * are scanned. + */ + nodemask_t *nodemask; +}; + +#define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) + +#ifdef ARCH_HAS_PREFETCH +#define prefetch_prev_lru_page(_page, _base, _field) \ + do { \ + if ((_page)->lru.prev != _base) { \ + struct page *prev; \ + \ + prev = lru_to_page(&(_page->lru)); \ + prefetch(&prev->_field); \ + } \ + } while (0) +#else +#define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) +#endif + +#ifdef ARCH_HAS_PREFETCHW +#define prefetchw_prev_lru_page(_page, _base, _field) \ + do { \ + if ((_page)->lru.prev != _base) { \ + struct page *prev; \ + \ + prev = lru_to_page(&(_page->lru)); \ + prefetchw(&prev->_field); \ + } \ + } while (0) +#else +#define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) +#endif + +/* + * From 0 .. 100. Higher means more swappy. + */ +int vm_swappiness = 60; +long vm_total_pages; /* The total number of pages which the VM controls */ + +static LIST_HEAD(shrinker_list); +static DECLARE_RWSEM(shrinker_rwsem); + +#ifdef CONFIG_CGROUP_MEM_RES_CTLR +#define scanning_global_lru(sc) (!(sc)->mem_cgroup) +#else +#define scanning_global_lru(sc) (1) +#endif + +static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone, + struct scan_control *sc) +{ + if (!scanning_global_lru(sc)) + return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone); + + return &zone->reclaim_stat; +} + +static unsigned long zone_nr_lru_pages(struct zone *zone, + struct scan_control *sc, enum lru_list lru) +{ + if (!scanning_global_lru(sc)) + return mem_cgroup_zone_nr_lru_pages(sc->mem_cgroup, zone, lru); + + return zone_page_state(zone, NR_LRU_BASE + lru); +} + + +/* + * Add a shrinker callback to be called from the vm + */ +void register_shrinker(struct shrinker *shrinker) +{ + shrinker->nr = 0; + down_write(&shrinker_rwsem); + list_add_tail(&shrinker->list, &shrinker_list); + up_write(&shrinker_rwsem); +} +EXPORT_SYMBOL(register_shrinker); + +/* + * Remove one + */ +void unregister_shrinker(struct shrinker *shrinker) +{ + down_write(&shrinker_rwsem); + list_del(&shrinker->list); + up_write(&shrinker_rwsem); +} +EXPORT_SYMBOL(unregister_shrinker); + +static inline int do_shrinker_shrink(struct shrinker *shrinker, + struct shrink_control *sc, + unsigned long nr_to_scan) +{ + sc->nr_to_scan = nr_to_scan; + return (*shrinker->shrink)(shrinker, sc); +} + +#define SHRINK_BATCH 128 +/* + * Call the shrink functions to age shrinkable caches + * + * Here we assume it costs one seek to replace a lru page and that it also + * takes a seek to recreate a cache object. With this in mind we age equal + * percentages of the lru and ageable caches. This should balance the seeks + * generated by these structures. + * + * If the vm encountered mapped pages on the LRU it increase the pressure on + * slab to avoid swapping. + * + * We do weird things to avoid (scanned*seeks*entries) overflowing 32 bits. + * + * `lru_pages' represents the number of on-LRU pages in all the zones which + * are eligible for the caller's allocation attempt. It is used for balancing + * slab reclaim versus page reclaim. + * + * Returns the number of slab objects which we shrunk. + */ +unsigned long shrink_slab(struct shrink_control *shrink, + unsigned long nr_pages_scanned, + unsigned long lru_pages) +{ + struct shrinker *shrinker; + unsigned long ret = 0; + + if (nr_pages_scanned == 0) + nr_pages_scanned = SWAP_CLUSTER_MAX; + + if (!down_read_trylock(&shrinker_rwsem)) { + /* Assume we'll be able to shrink next time */ + ret = 1; + goto out; + } + + list_for_each_entry(shrinker, &shrinker_list, list) { + unsigned long long delta; + unsigned long total_scan; + unsigned long max_pass; + + max_pass = do_shrinker_shrink(shrinker, shrink, 0); + delta = (4 * nr_pages_scanned) / shrinker->seeks; + delta *= max_pass; + do_div(delta, lru_pages + 1); + shrinker->nr += delta; + if (shrinker->nr < 0) { + printk(KERN_ERR "shrink_slab: %pF negative objects to " + "delete nr=%ld\n", + shrinker->shrink, shrinker->nr); + shrinker->nr = max_pass; + } + + /* + * Avoid risking looping forever due to too large nr value: + * never try to free more than twice the estimate number of + * freeable entries. + */ + if (shrinker->nr > max_pass * 2) + shrinker->nr = max_pass * 2; + + total_scan = shrinker->nr; + shrinker->nr = 0; + + while (total_scan >= SHRINK_BATCH) { + long this_scan = SHRINK_BATCH; + int shrink_ret; + int nr_before; + + nr_before = do_shrinker_shrink(shrinker, shrink, 0); + shrink_ret = do_shrinker_shrink(shrinker, shrink, + this_scan); + if (shrink_ret == -1) + break; + if (shrink_ret < nr_before) + ret += nr_before - shrink_ret; + count_vm_events(SLABS_SCANNED, this_scan); + total_scan -= this_scan; + + cond_resched(); + } + + shrinker->nr += total_scan; + } + up_read(&shrinker_rwsem); +out: + cond_resched(); + return ret; +} + +static void set_reclaim_mode(int priority, struct scan_control *sc, + bool sync) +{ + reclaim_mode_t syncmode = sync ? RECLAIM_MODE_SYNC : RECLAIM_MODE_ASYNC; + + /* + * Initially assume we are entering either lumpy reclaim or + * reclaim/compaction.Depending on the order, we will either set the + * sync mode or just reclaim order-0 pages later. + */ + if (COMPACTION_BUILD) + sc->reclaim_mode = RECLAIM_MODE_COMPACTION; + else + sc->reclaim_mode = RECLAIM_MODE_LUMPYRECLAIM; + + /* + * Avoid using lumpy reclaim or reclaim/compaction if possible by + * restricting when its set to either costly allocations or when + * under memory pressure + */ + if (sc->order > PAGE_ALLOC_COSTLY_ORDER) + sc->reclaim_mode |= syncmode; + else if (sc->order && priority < DEF_PRIORITY - 2) + sc->reclaim_mode |= syncmode; + else + sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; +} + +static void reset_reclaim_mode(struct scan_control *sc) +{ + sc->reclaim_mode = RECLAIM_MODE_SINGLE | RECLAIM_MODE_ASYNC; +} + +static inline int is_page_cache_freeable(struct page *page) +{ + /* + * A freeable page cache page is referenced only by the caller + * that isolated the page, the page cache radix tree and + * optional buffer heads at page->private. + */ + return page_count(page) - page_has_private(page) == 2; +} + +static int may_write_to_queue(struct backing_dev_info *bdi, + struct scan_control *sc) +{ + if (current->flags & PF_SWAPWRITE) + return 1; + if (!bdi_write_congested(bdi)) + return 1; + if (bdi == current->backing_dev_info) + return 1; + + /* lumpy reclaim for hugepage often need a lot of write */ + if (sc->order > PAGE_ALLOC_COSTLY_ORDER) + return 1; + return 0; +} + +/* + * We detected a synchronous write error writing a page out. Probably + * -ENOSPC. We need to propagate that into the address_space for a subsequent + * fsync(), msync() or close(). + * + * The tricky part is that after writepage we cannot touch the mapping: nothing + * prevents it from being freed up. But we have a ref on the page and once + * that page is locked, the mapping is pinned. + * + * We're allowed to run sleeping lock_page() here because we know the caller has + * __GFP_FS. + */ +static void handle_write_error(struct address_space *mapping, + struct page *page, int error) +{ + lock_page(page); + if (page_mapping(page) == mapping) + mapping_set_error(mapping, error); + unlock_page(page); +} + +/* possible outcome of pageout() */ +typedef enum { + /* failed to write page out, page is locked */ + PAGE_KEEP, + /* move page to the active list, page is locked */ + PAGE_ACTIVATE, + /* page has been sent to the disk successfully, page is unlocked */ + PAGE_SUCCESS, + /* page is clean and locked */ + PAGE_CLEAN, +} pageout_t; + +/* + * pageout is called by shrink_page_list() for each dirty page. + * Calls ->writepage(). + */ +static pageout_t pageout(struct page *page, struct address_space *mapping, + struct scan_control *sc) +{ + /* + * If the page is dirty, only perform writeback if that write + * will be non-blocking. To prevent this allocation from being + * stalled by pagecache activity. But note that there may be + * stalls if we need to run get_block(). We could test + * PagePrivate for that. + * + * If this process is currently in __generic_file_aio_write() against + * this page's queue, we can perform writeback even if that + * will block. + * + * If the page is swapcache, write it back even if that would + * block, for some throttling. This happens by accident, because + * swap_backing_dev_info is bust: it doesn't reflect the + * congestion state of the swapdevs. Easy to fix, if needed. + */ + if (!is_page_cache_freeable(page)) + return PAGE_KEEP; + if (!mapping) { + /* + * Some data journaling orphaned pages can have + * page->mapping == NULL while being dirty with clean buffers. + */ + if (page_has_private(page)) { + if (try_to_free_buffers(page)) { + ClearPageDirty(page); + printk("%s: orphaned page\n", __func__); + return PAGE_CLEAN; + } + } + return PAGE_KEEP; + } + if (mapping->a_ops->writepage == NULL) + return PAGE_ACTIVATE; + if (!may_write_to_queue(mapping->backing_dev_info, sc)) + return PAGE_KEEP; + + if (clear_page_dirty_for_io(page)) { + int res; + struct writeback_control wbc = { + .sync_mode = WB_SYNC_NONE, + .nr_to_write = SWAP_CLUSTER_MAX, + .range_start = 0, + .range_end = LLONG_MAX, + .for_reclaim = 1, + }; + + SetPageReclaim(page); + res = mapping->a_ops->writepage(page, &wbc); + if (res < 0) + handle_write_error(mapping, page, res); + if (res == AOP_WRITEPAGE_ACTIVATE) { + ClearPageReclaim(page); + return PAGE_ACTIVATE; + } + + /* + * Wait on writeback if requested to. This happens when + * direct reclaiming a large contiguous area and the + * first attempt to free a range of pages fails. + */ + if (PageWriteback(page) && + (sc->reclaim_mode & RECLAIM_MODE_SYNC)) + wait_on_page_writeback(page); + + if (!PageWriteback(page)) { + /* synchronous write or broken a_ops? */ + ClearPageReclaim(page); + } + trace_mm_vmscan_writepage(page, + trace_reclaim_flags(page, sc->reclaim_mode)); + inc_zone_page_state(page, NR_VMSCAN_WRITE); + return PAGE_SUCCESS; + } + + return PAGE_CLEAN; +} + +/* + * Same as remove_mapping, but if the page is removed from the mapping, it + * gets returned with a refcount of 0. + */ +static int __remove_mapping(struct address_space *mapping, struct page *page) +{ + BUG_ON(!PageLocked(page)); + BUG_ON(mapping != page_mapping(page)); + + spin_lock_irq(&mapping->tree_lock); + /* + * The non racy check for a busy page. + * + * Must be careful with the order of the tests. When someone has + * a ref to the page, it may be possible that they dirty it then + * drop the reference. So if PageDirty is tested before page_count + * here, then the following race may occur: + * + * get_user_pages(&page); + * [user mapping goes away] + * write_to(page); + * !PageDirty(page) [good] + * SetPageDirty(page); + * put_page(page); + * !page_count(page) [good, discard it] + * + * [oops, our write_to data is lost] + * + * Reversing the order of the tests ensures such a situation cannot + * escape unnoticed. The smp_rmb is needed to ensure the page->flags + * load is not satisfied before that of page->_count. + * + * Note that if SetPageDirty is always performed via set_page_dirty, + * and thus under tree_lock, then this ordering is not required. + */ + if (!page_freeze_refs(page, 2)) + goto cannot_free; + /* note: atomic_cmpxchg in page_freeze_refs provides the smp_rmb */ + if (unlikely(PageDirty(page))) { + page_unfreeze_refs(page, 2); + goto cannot_free; + } + + if (PageSwapCache(page)) { + swp_entry_t swap = { .val = page_private(page) }; + __delete_from_swap_cache(page); + spin_unlock_irq(&mapping->tree_lock); + swapcache_free(swap, page); + } else { + void (*freepage)(struct page *); + + freepage = mapping->a_ops->freepage; + + __delete_from_page_cache(page); + spin_unlock_irq(&mapping->tree_lock); + mem_cgroup_uncharge_cache_page(page); + + if (freepage != NULL) + freepage(page); + } + + return 1; + +cannot_free: + spin_unlock_irq(&mapping->tree_lock); + return 0; +} + +/* + * Attempt to detach a locked page from its ->mapping. If it is dirty or if + * someone else has a ref on the page, abort and return 0. If it was + * successfully detached, return 1. Assumes the caller has a single ref on + * this page. + */ +int remove_mapping(struct address_space *mapping, struct page *page) +{ + if (__remove_mapping(mapping, page)) { + /* + * Unfreezing the refcount with 1 rather than 2 effectively + * drops the pagecache ref for us without requiring another + * atomic operation. + */ + page_unfreeze_refs(page, 1); + return 1; + } + return 0; +} + +/** + * putback_lru_page - put previously isolated page onto appropriate LRU list + * @page: page to be put back to appropriate lru list + * + * Add previously isolated @page to appropriate LRU list. + * Page may still be unevictable for other reasons. + * + * lru_lock must not be held, interrupts must be enabled. + */ +void putback_lru_page(struct page *page) +{ + int lru; + int active = !!TestClearPageActive(page); + int was_unevictable = PageUnevictable(page); + + VM_BUG_ON(PageLRU(page)); + +redo: + ClearPageUnevictable(page); + + if (page_evictable(page, NULL)) { + /* + * For evictable pages, we can use the cache. + * In event of a race, worst case is we end up with an + * unevictable page on [in]active list. + * We know how to handle that. + */ + lru = active + page_lru_base_type(page); + lru_cache_add_lru(page, lru); + } else { + /* + * Put unevictable pages directly on zone's unevictable + * list. + */ + lru = LRU_UNEVICTABLE; + add_page_to_unevictable_list(page); + /* + * When racing with an mlock clearing (page is + * unlocked), make sure that if the other thread does + * not observe our setting of PG_lru and fails + * isolation, we see PG_mlocked cleared below and move + * the page back to the evictable list. + * + * The other side is TestClearPageMlocked(). + */ + smp_mb(); + } + + /* + * page's status can change while we move it among lru. If an evictable + * page is on unevictable list, it never be freed. To avoid that, + * check after we added it to the list, again. + */ + if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) { + if (!isolate_lru_page(page)) { + put_page(page); + goto redo; + } + /* This means someone else dropped this page from LRU + * So, it will be freed or putback to LRU again. There is + * nothing to do here. + */ + } + + if (was_unevictable && lru != LRU_UNEVICTABLE) + count_vm_event(UNEVICTABLE_PGRESCUED); + else if (!was_unevictable && lru == LRU_UNEVICTABLE) + count_vm_event(UNEVICTABLE_PGCULLED); + + put_page(page); /* drop ref from isolate */ +} + +enum page_references { + PAGEREF_RECLAIM, + PAGEREF_RECLAIM_CLEAN, + PAGEREF_KEEP, + PAGEREF_ACTIVATE, +}; + +static enum page_references page_check_references(struct page *page, + struct scan_control *sc) +{ + int referenced_ptes, referenced_page; + unsigned long vm_flags; + + referenced_ptes = page_referenced(page, 1, sc->mem_cgroup, &vm_flags); + referenced_page = TestClearPageReferenced(page); + + /* Lumpy reclaim - ignore references */ + if (sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM) + return PAGEREF_RECLAIM; + + /* + * Mlock lost the isolation race with us. Let try_to_unmap() + * move the page to the unevictable list. + */ + if (vm_flags & VM_LOCKED) + return PAGEREF_RECLAIM; + + if (referenced_ptes) { + if (PageSwapBacked(page)) + return PAGEREF_ACTIVATE; + /* + * All mapped pages start out with page table + * references from the instantiating fault, so we need + * to look twice if a mapped file page is used more + * than once. + * + * Mark it and spare it for another trip around the + * inactive list. Another page table reference will + * lead to its activation. + * + * Note: the mark is set for activated pages as well + * so that recently deactivated but used pages are + * quickly recovered. + */ + SetPageReferenced(page); + + if (referenced_page) + return PAGEREF_ACTIVATE; + + return PAGEREF_KEEP; + } + + /* Reclaim if clean, defer dirty pages to writeback */ + if (referenced_page && !PageSwapBacked(page)) + return PAGEREF_RECLAIM_CLEAN; + + return PAGEREF_RECLAIM; +} + +static noinline_for_stack void free_page_list(struct list_head *free_pages) +{ + struct pagevec freed_pvec; + struct page *page, *tmp; + + pagevec_init(&freed_pvec, 1); + + list_for_each_entry_safe(page, tmp, free_pages, lru) { + list_del(&page->lru); + if (!pagevec_add(&freed_pvec, page)) { + __pagevec_free(&freed_pvec); + pagevec_reinit(&freed_pvec); + } + } + + pagevec_free(&freed_pvec); +} + +/* + * shrink_page_list() returns the number of reclaimed pages + */ +static unsigned long shrink_page_list(struct list_head *page_list, + struct zone *zone, + struct scan_control *sc) +{ + LIST_HEAD(ret_pages); + LIST_HEAD(free_pages); + int pgactivate = 0; + unsigned long nr_dirty = 0; + unsigned long nr_congested = 0; + unsigned long nr_reclaimed = 0; + + cond_resched(); + + while (!list_empty(page_list)) { + enum page_references references; + struct address_space *mapping; + struct page *page; + int may_enter_fs; + + cond_resched(); + + page = lru_to_page(page_list); + list_del(&page->lru); + + if (!trylock_page(page)) + goto keep; + + VM_BUG_ON(PageActive(page)); + VM_BUG_ON(page_zone(page) != zone); + + sc->nr_scanned++; + + if (unlikely(!page_evictable(page, NULL))) + goto cull_mlocked; + + if (!sc->may_unmap && page_mapped(page)) + goto keep_locked; + + /* Double the slab pressure for mapped and swapcache pages */ + if (page_mapped(page) || PageSwapCache(page)) + sc->nr_scanned++; + + may_enter_fs = (sc->gfp_mask & __GFP_FS) || + (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); + + if (PageWriteback(page)) { + /* + * Synchronous reclaim is performed in two passes, + * first an asynchronous pass over the list to + * start parallel writeback, and a second synchronous + * pass to wait for the IO to complete. Wait here + * for any page for which writeback has already + * started. + */ + if ((sc->reclaim_mode & RECLAIM_MODE_SYNC) && + may_enter_fs) + wait_on_page_writeback(page); + else { + unlock_page(page); + goto keep_lumpy; + } + } + + references = page_check_references(page, sc); + switch (references) { + case PAGEREF_ACTIVATE: + goto activate_locked; + case PAGEREF_KEEP: + goto keep_locked; + case PAGEREF_RECLAIM: + case PAGEREF_RECLAIM_CLEAN: + ; /* try to reclaim the page below */ + } + + /* + * Anonymous process memory has backing store? + * Try to allocate it some swap space here. + */ + if (PageAnon(page) && !PageSwapCache(page)) { + if (!(sc->gfp_mask & __GFP_IO)) + goto keep_locked; + if (!add_to_swap(page)) + goto activate_locked; + may_enter_fs = 1; + } + + mapping = page_mapping(page); + + /* + * The page is mapped into the page tables of one or more + * processes. Try to unmap it here. + */ + if (page_mapped(page) && mapping) { + switch (try_to_unmap(page, TTU_UNMAP)) { + case SWAP_FAIL: + goto activate_locked; + case SWAP_AGAIN: + goto keep_locked; + case SWAP_MLOCK: + goto cull_mlocked; + case SWAP_SUCCESS: + ; /* try to free the page below */ + } + } + + if (PageDirty(page)) { + nr_dirty++; + + if (references == PAGEREF_RECLAIM_CLEAN) + goto keep_locked; + if (!may_enter_fs) + goto keep_locked; + if (!sc->may_writepage) + goto keep_locked; + + /* Page is dirty, try to write it out here */ + switch (pageout(page, mapping, sc)) { + case PAGE_KEEP: + nr_congested++; + goto keep_locked; + case PAGE_ACTIVATE: + goto activate_locked; + case PAGE_SUCCESS: + if (PageWriteback(page)) + goto keep_lumpy; + if (PageDirty(page)) + goto keep; + + /* + * A synchronous write - probably a ramdisk. Go + * ahead and try to reclaim the page. + */ + if (!trylock_page(page)) + goto keep; + if (PageDirty(page) || PageWriteback(page)) + goto keep_locked; + mapping = page_mapping(page); + case PAGE_CLEAN: + ; /* try to free the page below */ + } + } + + /* + * If the page has buffers, try to free the buffer mappings + * associated with this page. If we succeed we try to free + * the page as well. + * + * We do this even if the page is PageDirty(). + * try_to_release_page() does not perform I/O, but it is + * possible for a page to have PageDirty set, but it is actually + * clean (all its buffers are clean). This happens if the + * buffers were written out directly, with submit_bh(). ext3 + * will do this, as well as the blockdev mapping. + * try_to_release_page() will discover that cleanness and will + * drop the buffers and mark the page clean - it can be freed. + * + * Rarely, pages can have buffers and no ->mapping. These are + * the pages which were not successfully invalidated in + * truncate_complete_page(). We try to drop those buffers here + * and if that worked, and the page is no longer mapped into + * process address space (page_count == 1) it can be freed. + * Otherwise, leave the page on the LRU so it is swappable. + */ + if (page_has_private(page)) { + if (!try_to_release_page(page, sc->gfp_mask)) + goto activate_locked; + if (!mapping && page_count(page) == 1) { + unlock_page(page); + if (put_page_testzero(page)) + goto free_it; + else { + /* + * rare race with speculative reference. + * the speculative reference will free + * this page shortly, so we may + * increment nr_reclaimed here (and + * leave it off the LRU). + */ + nr_reclaimed++; + continue; + } + } + } + + if (!mapping || !__remove_mapping(mapping, page)) + goto keep_locked; + + /* + * At this point, we have no other references and there is + * no way to pick any more up (removed from LRU, removed + * from pagecache). Can use non-atomic bitops now (and + * we obviously don't have to worry about waking up a process + * waiting on the page lock, because there are no references. + */ + __clear_page_locked(page); +free_it: + nr_reclaimed++; + + /* + * Is there need to periodically free_page_list? It would + * appear not as the counts should be low + */ + list_add(&page->lru, &free_pages); + continue; + +cull_mlocked: + if (PageSwapCache(page)) + try_to_free_swap(page); + unlock_page(page); + putback_lru_page(page); + reset_reclaim_mode(sc); + continue; + +activate_locked: + /* Not a candidate for swapping, so reclaim swap space. */ + if (PageSwapCache(page) && vm_swap_full()) + try_to_free_swap(page); + VM_BUG_ON(PageActive(page)); + SetPageActive(page); + pgactivate++; +keep_locked: + unlock_page(page); +keep: + reset_reclaim_mode(sc); +keep_lumpy: + list_add(&page->lru, &ret_pages); + VM_BUG_ON(PageLRU(page) || PageUnevictable(page)); + } + + /* + * Tag a zone as congested if all the dirty pages encountered were + * backed by a congested BDI. In this case, reclaimers should just + * back off and wait for congestion to clear because further reclaim + * will encounter the same problem + */ + if (nr_dirty && nr_dirty == nr_congested && scanning_global_lru(sc)) + zone_set_flag(zone, ZONE_CONGESTED); + + free_page_list(&free_pages); + + list_splice(&ret_pages, page_list); + count_vm_events(PGACTIVATE, pgactivate); + return nr_reclaimed; +} + +/* + * Attempt to remove the specified page from its LRU. Only take this page + * if it is of the appropriate PageActive status. Pages which are being + * freed elsewhere are also ignored. + * + * page: page to consider + * mode: one of the LRU isolation modes defined above + * + * returns 0 on success, -ve errno on failure. + */ +int __isolate_lru_page(struct page *page, int mode, int file) +{ + int ret = -EINVAL; + + /* Only take pages on the LRU. */ + if (!PageLRU(page)) + return ret; + + /* + * When checking the active state, we need to be sure we are + * dealing with comparible boolean values. Take the logical not + * of each. + */ + if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode)) + return ret; + + if (mode != ISOLATE_BOTH && page_is_file_cache(page) != file) + return ret; + + /* + * When this function is being called for lumpy reclaim, we + * initially look into all LRU pages, active, inactive and + * unevictable; only give shrink_page_list evictable pages. + */ + if (PageUnevictable(page)) + return ret; + + ret = -EBUSY; + + if (likely(get_page_unless_zero(page))) { + /* + * 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. + */ + ClearPageLRU(page); + ret = 0; + } + + return ret; +} + +/* + * zone->lru_lock is heavily contended. Some of the functions that + * shrink the lists perform better by taking out a batch of pages + * and working on them outside the LRU lock. + * + * For pagecache intensive workloads, this function is the hottest + * spot in the kernel (apart from copy_*_user functions). + * + * Appropriate locks must be held before calling this function. + * + * @nr_to_scan: The number of pages to look through on the list. + * @src: The LRU list to pull pages off. + * @dst: The temp list to put pages on to. + * @scanned: The number of pages that were scanned. + * @order: The caller's attempted allocation order + * @mode: One of the LRU isolation modes + * @file: True [1] if isolating file [!anon] pages + * + * returns how many pages were moved onto *@dst. + */ +static unsigned long isolate_lru_pages(unsigned long nr_to_scan, + struct list_head *src, struct list_head *dst, + unsigned long *scanned, int order, int mode, int file) +{ + unsigned long nr_taken = 0; + unsigned long nr_lumpy_taken = 0; + unsigned long nr_lumpy_dirty = 0; + unsigned long nr_lumpy_failed = 0; + unsigned long scan; + + for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) { + struct page *page; + unsigned long pfn; + unsigned long end_pfn; + unsigned long page_pfn; + int zone_id; + + page = lru_to_page(src); + prefetchw_prev_lru_page(page, src, flags); + + VM_BUG_ON(!PageLRU(page)); + + switch (__isolate_lru_page(page, mode, file)) { + case 0: + list_move(&page->lru, dst); + mem_cgroup_del_lru(page); + nr_taken += hpage_nr_pages(page); + break; + + case -EBUSY: + /* else it is being freed elsewhere */ + list_move(&page->lru, src); + mem_cgroup_rotate_lru_list(page, page_lru(page)); + continue; + + default: + BUG(); + } + + if (!order) + continue; + + /* + * Attempt to take all pages in the order aligned region + * surrounding the tag page. Only take those pages of + * the same active state as that tag page. We may safely + * round the target page pfn down to the requested order + * as the mem_map is guaranteed valid out to MAX_ORDER, + * where that page is in a different zone we will detect + * it from its zone id and abort this block scan. + */ + zone_id = page_zone_id(page); + page_pfn = page_to_pfn(page); + pfn = page_pfn & ~((1 << order) - 1); + end_pfn = pfn + (1 << order); + for (; pfn < end_pfn; pfn++) { + struct page *cursor_page; + + /* The target page is in the block, ignore it. */ + if (unlikely(pfn == page_pfn)) + continue; + + /* Avoid holes within the zone. */ + if (unlikely(!pfn_valid_within(pfn))) + break; + + cursor_page = pfn_to_page(pfn); + + /* Check that we have not crossed a zone boundary. */ + if (unlikely(page_zone_id(cursor_page) != zone_id)) + break; + + /* + * If we don't have enough swap space, reclaiming of + * anon page which don't already have a swap slot is + * pointless. + */ + if (nr_swap_pages <= 0 && PageAnon(cursor_page) && + !PageSwapCache(cursor_page)) + break; + + if (__isolate_lru_page(cursor_page, mode, file) == 0) { + list_move(&cursor_page->lru, dst); + mem_cgroup_del_lru(cursor_page); + nr_taken += hpage_nr_pages(page); + nr_lumpy_taken++; + if (PageDirty(cursor_page)) + nr_lumpy_dirty++; + scan++; + } else { + /* + * Check if the page is freed already. + * + * We can't use page_count() as that + * requires compound_head and we don't + * have a pin on the page here. If a + * page is tail, we may or may not + * have isolated the head, so assume + * it's not free, it'd be tricky to + * track the head status without a + * page pin. + */ + if (!PageTail(cursor_page) && + !atomic_read(&cursor_page->_count)) + continue; + break; + } + } + + /* If we break out of the loop above, lumpy reclaim failed */ + if (pfn < end_pfn) + nr_lumpy_failed++; + } + + *scanned = scan; + + trace_mm_vmscan_lru_isolate(order, + nr_to_scan, scan, + nr_taken, + nr_lumpy_taken, nr_lumpy_dirty, nr_lumpy_failed, + mode); + return nr_taken; +} + +static unsigned long isolate_pages_global(unsigned long nr, + struct list_head *dst, + unsigned long *scanned, int order, + int mode, struct zone *z, + int active, int file) +{ + int lru = LRU_BASE; + if (active) + lru += LRU_ACTIVE; + if (file) + lru += LRU_FILE; + return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order, + mode, file); +} + +/* + * clear_active_flags() is a helper for shrink_active_list(), clearing + * any active bits from the pages in the list. + */ +static unsigned long clear_active_flags(struct list_head *page_list, + unsigned int *count) +{ + int nr_active = 0; + int lru; + struct page *page; + + list_for_each_entry(page, page_list, lru) { + int numpages = hpage_nr_pages(page); + lru = page_lru_base_type(page); + if (PageActive(page)) { + lru += LRU_ACTIVE; + ClearPageActive(page); + nr_active += numpages; + } + if (count) + count[lru] += numpages; + } + + return nr_active; +} + +/** + * isolate_lru_page - tries to isolate a page from its LRU list + * @page: page to isolate from its LRU list + * + * Isolates a @page from an LRU list, clears PageLRU and adjusts the + * vmstat statistic corresponding to whatever LRU list the page was on. + * + * Returns 0 if the page was removed from an LRU list. + * Returns -EBUSY if the page was not on an LRU list. + * + * The returned page will have PageLRU() cleared. If it was found on + * the active list, it will have PageActive set. If it was found on + * the unevictable list, it will have the PageUnevictable bit set. That flag + * may need to be cleared by the caller before letting the page go. + * + * The vmstat statistic corresponding to the list on which the page was + * found will be decremented. + * + * Restrictions: + * (1) Must be called with an elevated refcount on the page. This is a + * fundamentnal difference from isolate_lru_pages (which is called + * without a stable reference). + * (2) the lru_lock must not be held. + * (3) interrupts must be enabled. + */ +int isolate_lru_page(struct page *page) +{ + int ret = -EBUSY; + + VM_BUG_ON(!page_count(page)); + + if (PageLRU(page)) { + struct zone *zone = page_zone(page); + + spin_lock_irq(&zone->lru_lock); + if (PageLRU(page)) { + int lru = page_lru(page); + ret = 0; + get_page(page); + ClearPageLRU(page); + + del_page_from_lru_list(zone, page, lru); + } + spin_unlock_irq(&zone->lru_lock); + } + return ret; +} + +/* + * Are there way too many processes in the direct reclaim path already? + */ +static int too_many_isolated(struct zone *zone, int file, + struct scan_control *sc) +{ + unsigned long inactive, isolated; + + if (current_is_kswapd()) + return 0; + + if (!scanning_global_lru(sc)) + return 0; + + if (file) { + inactive = zone_page_state(zone, NR_INACTIVE_FILE); + isolated = zone_page_state(zone, NR_ISOLATED_FILE); + } else { + inactive = zone_page_state(zone, NR_INACTIVE_ANON); + isolated = zone_page_state(zone, NR_ISOLATED_ANON); + } + + return isolated > inactive; +} + +/* + * TODO: Try merging with migrations version of putback_lru_pages + */ +static noinline_for_stack void +putback_lru_pages(struct zone *zone, struct scan_control *sc, + unsigned long nr_anon, unsigned long nr_file, + struct list_head *page_list) +{ + struct page *page; + struct pagevec pvec; + struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); + + pagevec_init(&pvec, 1); + + /* + * Put back any unfreeable pages. + */ + spin_lock(&zone->lru_lock); + while (!list_empty(page_list)) { + int lru; + page = lru_to_page(page_list); + VM_BUG_ON(PageLRU(page)); + list_del(&page->lru); + if (unlikely(!page_evictable(page, NULL))) { + spin_unlock_irq(&zone->lru_lock); + putback_lru_page(page); + spin_lock_irq(&zone->lru_lock); + continue; + } + SetPageLRU(page); + lru = page_lru(page); + add_page_to_lru_list(zone, page, lru); + if (is_active_lru(lru)) { + int file = is_file_lru(lru); + int numpages = hpage_nr_pages(page); + reclaim_stat->recent_rotated[file] += numpages; + } + if (!pagevec_add(&pvec, page)) { + spin_unlock_irq(&zone->lru_lock); + __pagevec_release(&pvec); + spin_lock_irq(&zone->lru_lock); + } + } + __mod_zone_page_state(zone, NR_ISOLATED_ANON, -nr_anon); + __mod_zone_page_state(zone, NR_ISOLATED_FILE, -nr_file); + + spin_unlock_irq(&zone->lru_lock); + pagevec_release(&pvec); +} + +static noinline_for_stack void update_isolated_counts(struct zone *zone, + struct scan_control *sc, + unsigned long *nr_anon, + unsigned long *nr_file, + struct list_head *isolated_list) +{ + unsigned long nr_active; + unsigned int count[NR_LRU_LISTS] = { 0, }; + struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); + + nr_active = clear_active_flags(isolated_list, count); + __count_vm_events(PGDEACTIVATE, nr_active); + + __mod_zone_page_state(zone, NR_ACTIVE_FILE, + -count[LRU_ACTIVE_FILE]); + __mod_zone_page_state(zone, NR_INACTIVE_FILE, + -count[LRU_INACTIVE_FILE]); + __mod_zone_page_state(zone, NR_ACTIVE_ANON, + -count[LRU_ACTIVE_ANON]); + __mod_zone_page_state(zone, NR_INACTIVE_ANON, + -count[LRU_INACTIVE_ANON]); + + *nr_anon = count[LRU_ACTIVE_ANON] + count[LRU_INACTIVE_ANON]; + *nr_file = count[LRU_ACTIVE_FILE] + count[LRU_INACTIVE_FILE]; + __mod_zone_page_state(zone, NR_ISOLATED_ANON, *nr_anon); + __mod_zone_page_state(zone, NR_ISOLATED_FILE, *nr_file); + + reclaim_stat->recent_scanned[0] += *nr_anon; + reclaim_stat->recent_scanned[1] += *nr_file; +} + +/* + * Returns true if the caller should wait to clean dirty/writeback pages. + * + * If we are direct reclaiming for contiguous pages and we do not reclaim + * everything in the list, try again and wait for writeback IO to complete. + * This will stall high-order allocations noticeably. Only do that when really + * need to free the pages under high memory pressure. + */ +static inline bool should_reclaim_stall(unsigned long nr_taken, + unsigned long nr_freed, + int priority, + struct scan_control *sc) +{ + int lumpy_stall_priority; + + /* kswapd should not stall on sync IO */ + if (current_is_kswapd()) + return false; + + /* Only stall on lumpy reclaim */ + if (sc->reclaim_mode & RECLAIM_MODE_SINGLE) + return false; + + /* If we have relaimed everything on the isolated list, no stall */ + if (nr_freed == nr_taken) + return false; + + /* + * For high-order allocations, there are two stall thresholds. + * High-cost allocations stall immediately where as lower + * order allocations such as stacks require the scanning + * priority to be much higher before stalling. + */ + if (sc->order > PAGE_ALLOC_COSTLY_ORDER) + lumpy_stall_priority = DEF_PRIORITY; + else + lumpy_stall_priority = DEF_PRIORITY / 3; + + return priority <= lumpy_stall_priority; +} + +/* + * shrink_inactive_list() is a helper for shrink_zone(). It returns the number + * of reclaimed pages + */ +static noinline_for_stack unsigned long +shrink_inactive_list(unsigned long nr_to_scan, struct zone *zone, + struct scan_control *sc, int priority, int file) +{ + LIST_HEAD(page_list); + unsigned long nr_scanned; + unsigned long nr_reclaimed = 0; + unsigned long nr_taken; + unsigned long nr_anon; + unsigned long nr_file; + + while (unlikely(too_many_isolated(zone, file, sc))) { + congestion_wait(BLK_RW_ASYNC, HZ/10); + + /* We are about to die and free our memory. Return now. */ + if (fatal_signal_pending(current)) + return SWAP_CLUSTER_MAX; + } + + set_reclaim_mode(priority, sc, false); + lru_add_drain(); + spin_lock_irq(&zone->lru_lock); + + if (scanning_global_lru(sc)) { + nr_taken = isolate_pages_global(nr_to_scan, + &page_list, &nr_scanned, sc->order, + sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ? + ISOLATE_BOTH : ISOLATE_INACTIVE, + zone, 0, file); + zone->pages_scanned += nr_scanned; + if (current_is_kswapd()) + __count_zone_vm_events(PGSCAN_KSWAPD, zone, + nr_scanned); + else + __count_zone_vm_events(PGSCAN_DIRECT, zone, + nr_scanned); + } else { + nr_taken = mem_cgroup_isolate_pages(nr_to_scan, + &page_list, &nr_scanned, sc->order, + sc->reclaim_mode & RECLAIM_MODE_LUMPYRECLAIM ? + ISOLATE_BOTH : ISOLATE_INACTIVE, + zone, sc->mem_cgroup, + 0, file); + /* + * mem_cgroup_isolate_pages() keeps track of + * scanned pages on its own. + */ + } + + if (nr_taken == 0) { + spin_unlock_irq(&zone->lru_lock); + return 0; + } + + update_isolated_counts(zone, sc, &nr_anon, &nr_file, &page_list); + + spin_unlock_irq(&zone->lru_lock); + + nr_reclaimed = shrink_page_list(&page_list, zone, sc); + + /* Check if we should syncronously wait for writeback */ + if (should_reclaim_stall(nr_taken, nr_reclaimed, priority, sc)) { + set_reclaim_mode(priority, sc, true); + nr_reclaimed += shrink_page_list(&page_list, zone, sc); + } + + local_irq_disable(); + if (current_is_kswapd()) + __count_vm_events(KSWAPD_STEAL, nr_reclaimed); + __count_zone_vm_events(PGSTEAL, zone, nr_reclaimed); + + putback_lru_pages(zone, sc, nr_anon, nr_file, &page_list); + + trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id, + zone_idx(zone), + nr_scanned, nr_reclaimed, + priority, + trace_shrink_flags(file, sc->reclaim_mode)); + return nr_reclaimed; +} + +/* + * This moves pages from the active list to the inactive list. + * + * We move them the other way if the page is referenced by one or more + * processes, from rmap. + * + * If the pages are mostly unmapped, the processing is fast and it is + * appropriate to hold zone->lru_lock across the whole operation. But if + * the pages are mapped, the processing is slow (page_referenced()) so we + * should drop zone->lru_lock around each page. It's impossible to balance + * this, so instead we remove the pages from the LRU while processing them. + * It is safe to rely on PG_active against the non-LRU pages in here because + * nobody will play with that bit on a non-LRU page. + * + * The downside is that we have to touch page->_count against each page. + * But we had to alter page->flags anyway. + */ + +static void move_active_pages_to_lru(struct zone *zone, + struct list_head *list, + enum lru_list lru) +{ + unsigned long pgmoved = 0; + struct pagevec pvec; + struct page *page; + + pagevec_init(&pvec, 1); + + while (!list_empty(list)) { + page = lru_to_page(list); + + VM_BUG_ON(PageLRU(page)); + SetPageLRU(page); + + list_move(&page->lru, &zone->lru[lru].list); + mem_cgroup_add_lru_list(page, lru); + pgmoved += hpage_nr_pages(page); + + if (!pagevec_add(&pvec, page) || list_empty(list)) { + spin_unlock_irq(&zone->lru_lock); + if (buffer_heads_over_limit) + pagevec_strip(&pvec); + __pagevec_release(&pvec); + spin_lock_irq(&zone->lru_lock); + } + } + __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved); + if (!is_active_lru(lru)) + __count_vm_events(PGDEACTIVATE, pgmoved); +} + +static void shrink_active_list(unsigned long nr_pages, struct zone *zone, + struct scan_control *sc, int priority, int file) +{ + unsigned long nr_taken; + unsigned long pgscanned; + unsigned long vm_flags; + LIST_HEAD(l_hold); /* The pages which were snipped off */ + LIST_HEAD(l_active); + LIST_HEAD(l_inactive); + struct page *page; + struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); + unsigned long nr_rotated = 0; + + lru_add_drain(); + spin_lock_irq(&zone->lru_lock); + if (scanning_global_lru(sc)) { + nr_taken = isolate_pages_global(nr_pages, &l_hold, + &pgscanned, sc->order, + ISOLATE_ACTIVE, zone, + 1, file); + zone->pages_scanned += pgscanned; + } else { + nr_taken = mem_cgroup_isolate_pages(nr_pages, &l_hold, + &pgscanned, sc->order, + ISOLATE_ACTIVE, zone, + sc->mem_cgroup, 1, file); + /* + * mem_cgroup_isolate_pages() keeps track of + * scanned pages on its own. + */ + } + + reclaim_stat->recent_scanned[file] += nr_taken; + + __count_zone_vm_events(PGREFILL, zone, pgscanned); + if (file) + __mod_zone_page_state(zone, NR_ACTIVE_FILE, -nr_taken); + else + __mod_zone_page_state(zone, NR_ACTIVE_ANON, -nr_taken); + __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken); + spin_unlock_irq(&zone->lru_lock); + + while (!list_empty(&l_hold)) { + cond_resched(); + page = lru_to_page(&l_hold); + list_del(&page->lru); + + if (unlikely(!page_evictable(page, NULL))) { + putback_lru_page(page); + continue; + } + + if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) { + nr_rotated += hpage_nr_pages(page); + /* + * Identify referenced, file-backed active pages and + * give them one more trip around the active list. So + * that executable code get better chances to stay in + * memory under moderate memory pressure. Anon pages + * are not likely to be evicted by use-once streaming + * IO, plus JVM can create lots of anon VM_EXEC pages, + * so we ignore them here. + */ + if ((vm_flags & VM_EXEC) && page_is_file_cache(page)) { + list_add(&page->lru, &l_active); + continue; + } + } + + ClearPageActive(page); /* we are de-activating */ + list_add(&page->lru, &l_inactive); + } + + /* + * Move pages back to the lru list. + */ + spin_lock_irq(&zone->lru_lock); + /* + * Count referenced pages from currently used mappings as rotated, + * even though only some of them are actually re-activated. This + * helps balance scan pressure between file and anonymous pages in + * get_scan_ratio. + */ + reclaim_stat->recent_rotated[file] += nr_rotated; + + move_active_pages_to_lru(zone, &l_active, + LRU_ACTIVE + file * LRU_FILE); + move_active_pages_to_lru(zone, &l_inactive, + LRU_BASE + file * LRU_FILE); + __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken); + spin_unlock_irq(&zone->lru_lock); +} + +#ifdef CONFIG_SWAP +static int inactive_anon_is_low_global(struct zone *zone) +{ + unsigned long active, inactive; + + active = zone_page_state(zone, NR_ACTIVE_ANON); + inactive = zone_page_state(zone, NR_INACTIVE_ANON); + + if (inactive * zone->inactive_ratio < active) + return 1; + + return 0; +} + +/** + * inactive_anon_is_low - check if anonymous pages need to be deactivated + * @zone: zone to check + * @sc: scan control of this context + * + * Returns true if the zone does not have enough inactive anon pages, + * meaning some active anon pages need to be deactivated. + */ +static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc) +{ + int low; + + /* + * If we don't have swap space, anonymous page deactivation + * is pointless. + */ + if (!total_swap_pages) + return 0; + + if (scanning_global_lru(sc)) + low = inactive_anon_is_low_global(zone); + else + low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup); + return low; +} +#else +static inline int inactive_anon_is_low(struct zone *zone, + struct scan_control *sc) +{ + return 0; +} +#endif + +static int inactive_file_is_low_global(struct zone *zone) +{ + unsigned long active, inactive; + + active = zone_page_state(zone, NR_ACTIVE_FILE); + inactive = zone_page_state(zone, NR_INACTIVE_FILE); + + return (active > inactive); +} + +/** + * inactive_file_is_low - check if file pages need to be deactivated + * @zone: zone to check + * @sc: scan control of this context + * + * When the system is doing streaming IO, memory pressure here + * ensures that active file pages get deactivated, until more + * than half of the file pages are on the inactive list. + * + * Once we get to that situation, protect the system's working + * set from being evicted by disabling active file page aging. + * + * This uses a different ratio than the anonymous pages, because + * the page cache uses a use-once replacement algorithm. + */ +static int inactive_file_is_low(struct zone *zone, struct scan_control *sc) +{ + int low; + + if (scanning_global_lru(sc)) + low = inactive_file_is_low_global(zone); + else + low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup); + return low; +} + +static int inactive_list_is_low(struct zone *zone, struct scan_control *sc, + int file) +{ + if (file) + return inactive_file_is_low(zone, sc); + else + return inactive_anon_is_low(zone, sc); +} + +static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, + struct zone *zone, struct scan_control *sc, int priority) +{ + int file = is_file_lru(lru); + + if (is_active_lru(lru)) { + if (inactive_list_is_low(zone, sc, file)) + shrink_active_list(nr_to_scan, zone, sc, priority, file); + return 0; + } + + return shrink_inactive_list(nr_to_scan, zone, sc, priority, file); +} + +/* + * Determine how aggressively the anon and file LRU lists should be + * scanned. The relative value of each set of LRU lists is determined + * by looking at the fraction of the pages scanned we did rotate back + * onto the active list instead of evict. + * + * nr[0] = anon pages to scan; nr[1] = file pages to scan + */ +static void get_scan_count(struct zone *zone, struct scan_control *sc, + unsigned long *nr, int priority) +{ + unsigned long anon, file, free; + unsigned long anon_prio, file_prio; + unsigned long ap, fp; + struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); + u64 fraction[2], denominator; + enum lru_list l; + int noswap = 0; + int force_scan = 0; + unsigned long nr_force_scan[2]; + + + anon = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_ANON) + + zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON); + file = zone_nr_lru_pages(zone, sc, LRU_ACTIVE_FILE) + + zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE); + + if (((anon + file) >> priority) < SWAP_CLUSTER_MAX) { + /* kswapd does zone balancing and need to scan this zone */ + if (scanning_global_lru(sc) && current_is_kswapd()) + force_scan = 1; + /* memcg may have small limit and need to avoid priority drop */ + if (!scanning_global_lru(sc)) + force_scan = 1; + } + + /* If we have no swap space, do not bother scanning anon pages. */ + if (!sc->may_swap || (nr_swap_pages <= 0)) { + noswap = 1; + fraction[0] = 0; + fraction[1] = 1; + denominator = 1; + nr_force_scan[0] = 0; + nr_force_scan[1] = SWAP_CLUSTER_MAX; + goto out; + } + + if (scanning_global_lru(sc)) { + free = zone_page_state(zone, NR_FREE_PAGES); + /* If we have very few page cache pages, + force-scan anon pages. */ + if (unlikely(file + free <= high_wmark_pages(zone))) { + fraction[0] = 1; + fraction[1] = 0; + denominator = 1; + nr_force_scan[0] = SWAP_CLUSTER_MAX; + nr_force_scan[1] = 0; + goto out; + } + } + + /* + * With swappiness at 100, anonymous and file have the same priority. + * This scanning priority is essentially the inverse of IO cost. + */ + anon_prio = sc->swappiness; + file_prio = 200 - sc->swappiness; + + /* + * OK, so we have swap space and a fair amount of page cache + * pages. We use the recently rotated / recently scanned + * ratios to determine how valuable each cache is. + * + * Because workloads change over time (and to avoid overflow) + * we keep these statistics as a floating average, which ends + * up weighing recent references more than old ones. + * + * anon in [0], file in [1] + */ + spin_lock_irq(&zone->lru_lock); + if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { + reclaim_stat->recent_scanned[0] /= 2; + reclaim_stat->recent_rotated[0] /= 2; + } + + if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { + reclaim_stat->recent_scanned[1] /= 2; + reclaim_stat->recent_rotated[1] /= 2; + } + + /* + * The amount of pressure on anon vs file pages is inversely + * proportional to the fraction of recently scanned pages on + * each list that were recently referenced and in active use. + */ + ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1); + ap /= reclaim_stat->recent_rotated[0] + 1; + + fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1); + fp /= reclaim_stat->recent_rotated[1] + 1; + spin_unlock_irq(&zone->lru_lock); + + fraction[0] = ap; + fraction[1] = fp; + denominator = ap + fp + 1; + if (force_scan) { + unsigned long scan = SWAP_CLUSTER_MAX; + nr_force_scan[0] = div64_u64(scan * ap, denominator); + nr_force_scan[1] = div64_u64(scan * fp, denominator); + } +out: + for_each_evictable_lru(l) { + int file = is_file_lru(l); + unsigned long scan; + + scan = zone_nr_lru_pages(zone, sc, l); + if (priority || noswap) { + scan >>= priority; + scan = div64_u64(scan * fraction[file], denominator); + } + + /* + * If zone is small or memcg is small, nr[l] can be 0. + * This results no-scan on this priority and priority drop down. + * For global direct reclaim, it can visit next zone and tend + * not to have problems. For global kswapd, it's for zone + * balancing and it need to scan a small amounts. When using + * memcg, priority drop can cause big latency. So, it's better + * to scan small amount. See may_noscan above. + */ + if (!scan && force_scan) + scan = nr_force_scan[file]; + nr[l] = scan; + } +} + +/* + * Reclaim/compaction depends on a number of pages being freed. To avoid + * disruption to the system, a small number of order-0 pages continue to be + * rotated and reclaimed in the normal fashion. However, by the time we get + * back to the allocator and call try_to_compact_zone(), we ensure that + * there are enough free pages for it to be likely successful + */ +static inline bool should_continue_reclaim(struct zone *zone, + unsigned long nr_reclaimed, + unsigned long nr_scanned, + struct scan_control *sc) +{ + unsigned long pages_for_compaction; + unsigned long inactive_lru_pages; + + /* If not in reclaim/compaction mode, stop */ + if (!(sc->reclaim_mode & RECLAIM_MODE_COMPACTION)) + return false; + + /* Consider stopping depending on scan and reclaim activity */ + if (sc->gfp_mask & __GFP_REPEAT) { + /* + * For __GFP_REPEAT allocations, stop reclaiming if the + * full LRU list has been scanned and we are still failing + * to reclaim pages. This full LRU scan is potentially + * expensive but a __GFP_REPEAT caller really wants to succeed + */ + if (!nr_reclaimed && !nr_scanned) + return false; + } else { + /* + * For non-__GFP_REPEAT allocations which can presumably + * fail without consequence, stop if we failed to reclaim + * any pages from the last SWAP_CLUSTER_MAX number of + * pages that were scanned. This will return to the + * caller faster at the risk reclaim/compaction and + * the resulting allocation attempt fails + */ + if (!nr_reclaimed) + return false; + } + + /* + * If we have not reclaimed enough pages for compaction and the + * inactive lists are large enough, continue reclaiming + */ + pages_for_compaction = (2UL << sc->order); + inactive_lru_pages = zone_nr_lru_pages(zone, sc, LRU_INACTIVE_ANON) + + zone_nr_lru_pages(zone, sc, LRU_INACTIVE_FILE); + if (sc->nr_reclaimed < pages_for_compaction && + inactive_lru_pages > pages_for_compaction) + return true; + + /* If compaction would go ahead or the allocation would succeed, stop */ + switch (compaction_suitable(zone, sc->order)) { + case COMPACT_PARTIAL: + case COMPACT_CONTINUE: + return false; + default: + return true; + } +} + +/* + * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. + */ +static void shrink_zone(int priority, struct zone *zone, + struct scan_control *sc) +{ + unsigned long nr[NR_LRU_LISTS]; + unsigned long nr_to_scan; + enum lru_list l; + unsigned long nr_reclaimed, nr_scanned; + unsigned long nr_to_reclaim = sc->nr_to_reclaim; + +restart: + nr_reclaimed = 0; + nr_scanned = sc->nr_scanned; + get_scan_count(zone, sc, nr, priority); + + while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || + nr[LRU_INACTIVE_FILE]) { + for_each_evictable_lru(l) { + if (nr[l]) { + nr_to_scan = min_t(unsigned long, + nr[l], SWAP_CLUSTER_MAX); + nr[l] -= nr_to_scan; + + nr_reclaimed += shrink_list(l, nr_to_scan, + zone, sc, priority); + } + } + /* + * On large memory systems, scan >> priority can become + * really large. This is fine for the starting priority; + * we want to put equal scanning pressure on each zone. + * However, if the VM has a harder time of freeing pages, + * with multiple processes reclaiming pages, the total + * freeing target can get unreasonably large. + */ + if (nr_reclaimed >= nr_to_reclaim && priority < DEF_PRIORITY) + break; + } + sc->nr_reclaimed += nr_reclaimed; + + /* + * Even if we did not try to evict anon pages at all, we want to + * rebalance the anon lru active/inactive ratio. + */ + if (inactive_anon_is_low(zone, sc)) + shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0); + + /* reclaim/compaction might need reclaim to continue */ + if (should_continue_reclaim(zone, nr_reclaimed, + sc->nr_scanned - nr_scanned, sc)) + goto restart; + + throttle_vm_writeout(sc->gfp_mask); +} + +/* + * This is the direct reclaim path, for page-allocating processes. We only + * try to reclaim pages from zones which will satisfy the caller's allocation + * request. + * + * We reclaim from a zone even if that zone is over high_wmark_pages(zone). + * Because: + * a) The caller may be trying to free *extra* pages to satisfy a higher-order + * allocation or + * b) The target zone may be at high_wmark_pages(zone) but the lower zones + * must go *over* high_wmark_pages(zone) to satisfy the `incremental min' + * zone defense algorithm. + * + * If a zone is deemed to be full of pinned pages then just give it a light + * scan then give up on it. + */ +static void shrink_zones(int priority, struct zonelist *zonelist, + struct scan_control *sc) +{ + struct zoneref *z; + struct zone *zone; + unsigned long nr_soft_reclaimed; + unsigned long nr_soft_scanned; + + for_each_zone_zonelist_nodemask(zone, z, zonelist, + gfp_zone(sc->gfp_mask), sc->nodemask) { + if (!populated_zone(zone)) + continue; + /* + * Take care memory controller reclaiming has small influence + * to global LRU. + */ + if (scanning_global_lru(sc)) { + if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) + continue; + if (zone->all_unreclaimable && priority != DEF_PRIORITY) + continue; /* Let kswapd poll it */ + /* + * This steals pages from memory cgroups over softlimit + * and returns the number of reclaimed pages and + * scanned pages. This works for global memory pressure + * and balancing, not for a memcg's limit. + */ + nr_soft_scanned = 0; + nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone, + sc->order, sc->gfp_mask, + &nr_soft_scanned); + sc->nr_reclaimed += nr_soft_reclaimed; + sc->nr_scanned += nr_soft_scanned; + /* need some check for avoid more shrink_zone() */ + } + + shrink_zone(priority, zone, sc); + } +} + +static bool zone_reclaimable(struct zone *zone) +{ + return zone->pages_scanned < zone_reclaimable_pages(zone) * 6; +} + +/* All zones in zonelist are unreclaimable? */ +static bool all_unreclaimable(struct zonelist *zonelist, + struct scan_control *sc) +{ + struct zoneref *z; + struct zone *zone; + + for_each_zone_zonelist_nodemask(zone, z, zonelist, + gfp_zone(sc->gfp_mask), sc->nodemask) { + if (!populated_zone(zone)) + continue; + if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) + continue; + if (!zone->all_unreclaimable) + return false; + } + + return true; +} + +/* + * This is the main entry point to direct page reclaim. + * + * If a full scan of the inactive list fails to free enough memory then we + * are "out of memory" and something needs to be killed. + * + * If the caller is !__GFP_FS then the probability of a failure is reasonably + * high - the zone may be full of dirty or under-writeback pages, which this + * caller can't do much about. We kick the writeback threads and take explicit + * naps in the hope that some of these pages can be written. But if the + * allocating task holds filesystem locks which prevent writeout this might not + * work, and the allocation attempt will fail. + * + * returns: 0, if no pages reclaimed + * else, the number of pages reclaimed + */ +static unsigned long do_try_to_free_pages(struct zonelist *zonelist, + struct scan_control *sc, + struct shrink_control *shrink) +{ + int priority; + unsigned long total_scanned = 0; + struct reclaim_state *reclaim_state = current->reclaim_state; + struct zoneref *z; + struct zone *zone; + unsigned long writeback_threshold; + + get_mems_allowed(); + delayacct_freepages_start(); + + if (scanning_global_lru(sc)) + count_vm_event(ALLOCSTALL); + + for (priority = DEF_PRIORITY; priority >= 0; priority--) { + sc->nr_scanned = 0; + if (!priority) + disable_swap_token(sc->mem_cgroup); + shrink_zones(priority, zonelist, sc); + /* + * Don't shrink slabs when reclaiming memory from + * over limit cgroups + */ + if (scanning_global_lru(sc)) { + unsigned long lru_pages = 0; + for_each_zone_zonelist(zone, z, zonelist, + gfp_zone(sc->gfp_mask)) { + if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) + continue; + + lru_pages += zone_reclaimable_pages(zone); + } + + shrink_slab(shrink, sc->nr_scanned, lru_pages); + if (reclaim_state) { + sc->nr_reclaimed += reclaim_state->reclaimed_slab; + reclaim_state->reclaimed_slab = 0; + } + } + total_scanned += sc->nr_scanned; + if (sc->nr_reclaimed >= sc->nr_to_reclaim) + goto out; + + /* + * Try to write back as many pages as we just scanned. This + * tends to cause slow streaming writers to write data to the + * disk smoothly, at the dirtying rate, which is nice. But + * that's undesirable in laptop mode, where we *want* lumpy + * writeout. So in laptop mode, write out the whole world. + */ + writeback_threshold = sc->nr_to_reclaim + sc->nr_to_reclaim / 2; + if (total_scanned > writeback_threshold) { + wakeup_flusher_threads(laptop_mode ? 0 : total_scanned); + sc->may_writepage = 1; + } + + /* Take a nap, wait for some writeback to complete */ + if (!sc->hibernation_mode && sc->nr_scanned && + priority < DEF_PRIORITY - 2) { + struct zone *preferred_zone; + + first_zones_zonelist(zonelist, gfp_zone(sc->gfp_mask), + &cpuset_current_mems_allowed, + &preferred_zone); + wait_iff_congested(preferred_zone, BLK_RW_ASYNC, HZ/10); + } + } + +out: + delayacct_freepages_end(); + put_mems_allowed(); + + if (sc->nr_reclaimed) + return sc->nr_reclaimed; + + /* + * As hibernation is going on, kswapd is freezed so that it can't mark + * the zone into all_unreclaimable. Thus bypassing all_unreclaimable + * check. + */ + if (oom_killer_disabled) + return 0; + + /* top priority shrink_zones still had more to do? don't OOM, then */ + if (scanning_global_lru(sc) && !all_unreclaimable(zonelist, sc)) + return 1; + + return 0; +} + +unsigned long try_to_free_pages(struct zonelist *zonelist, int order, + gfp_t gfp_mask, nodemask_t *nodemask) +{ + unsigned long nr_reclaimed; + struct scan_control sc = { + .gfp_mask = gfp_mask, + .may_writepage = !laptop_mode, + .nr_to_reclaim = SWAP_CLUSTER_MAX, + .may_unmap = 1, + .may_swap = 1, + .swappiness = vm_swappiness, + .order = order, + .mem_cgroup = NULL, + .nodemask = nodemask, + }; + struct shrink_control shrink = { + .gfp_mask = sc.gfp_mask, + }; + + trace_mm_vmscan_direct_reclaim_begin(order, + sc.may_writepage, + gfp_mask); + + nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); + + trace_mm_vmscan_direct_reclaim_end(nr_reclaimed); + + return nr_reclaimed; +} + +#ifdef CONFIG_CGROUP_MEM_RES_CTLR + +unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *mem, + gfp_t gfp_mask, bool noswap, + unsigned int swappiness, + struct zone *zone, + unsigned long *nr_scanned) +{ + struct scan_control sc = { + .nr_scanned = 0, + .nr_to_reclaim = SWAP_CLUSTER_MAX, + .may_writepage = !laptop_mode, + .may_unmap = 1, + .may_swap = !noswap, + .swappiness = swappiness, + .order = 0, + .mem_cgroup = mem, + }; + + sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | + (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); + + trace_mm_vmscan_memcg_softlimit_reclaim_begin(0, + sc.may_writepage, + sc.gfp_mask); + + /* + * NOTE: Although we can get the priority field, using it + * here is not a good idea, since it limits the pages we can scan. + * if we don't reclaim here, the shrink_zone from balance_pgdat + * will pick up pages from other mem cgroup's as well. We hack + * the priority and make it zero. + */ + shrink_zone(0, zone, &sc); + + trace_mm_vmscan_memcg_softlimit_reclaim_end(sc.nr_reclaimed); + + *nr_scanned = sc.nr_scanned; + return sc.nr_reclaimed; +} + +unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont, + gfp_t gfp_mask, + bool noswap, + unsigned int swappiness) +{ + struct zonelist *zonelist; + unsigned long nr_reclaimed; + int nid; + struct scan_control sc = { + .may_writepage = !laptop_mode, + .may_unmap = 1, + .may_swap = !noswap, + .nr_to_reclaim = SWAP_CLUSTER_MAX, + .swappiness = swappiness, + .order = 0, + .mem_cgroup = mem_cont, + .nodemask = NULL, /* we don't care the placement */ + .gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | + (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK), + }; + struct shrink_control shrink = { + .gfp_mask = sc.gfp_mask, + }; + + /* + * Unlike direct reclaim via alloc_pages(), memcg's reclaim doesn't + * take care of from where we get pages. So the node where we start the + * scan does not need to be the current node. + */ + nid = mem_cgroup_select_victim_node(mem_cont); + + zonelist = NODE_DATA(nid)->node_zonelists; + + trace_mm_vmscan_memcg_reclaim_begin(0, + sc.may_writepage, + sc.gfp_mask); + + nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); + + trace_mm_vmscan_memcg_reclaim_end(nr_reclaimed); + + return nr_reclaimed; +} +#endif + +/* + * pgdat_balanced is used when checking if a node is balanced for high-order + * allocations. Only zones that meet watermarks and are in a zone allowed + * by the callers classzone_idx are added to balanced_pages. The total of + * balanced pages must be at least 25% of the zones allowed by classzone_idx + * for the node to be considered balanced. Forcing all zones to be balanced + * for high orders can cause excessive reclaim when there are imbalanced zones. + * The choice of 25% is due to + * o a 16M DMA zone that is balanced will not balance a zone on any + * reasonable sized machine + * o On all other machines, the top zone must be at least a reasonable + * percentage of the middle zones. For example, on 32-bit x86, highmem + * would need to be at least 256M for it to be balance a whole node. + * Similarly, on x86-64 the Normal zone would need to be at least 1G + * to balance a node on its own. These seemed like reasonable ratios. + */ +static bool pgdat_balanced(pg_data_t *pgdat, unsigned long balanced_pages, + int classzone_idx) +{ + unsigned long present_pages = 0; + int i; + + for (i = 0; i <= classzone_idx; i++) + present_pages += pgdat->node_zones[i].present_pages; + + /* A special case here: if zone has no page, we think it's balanced */ + return balanced_pages >= (present_pages >> 2); +} + +/* is kswapd sleeping prematurely? */ +static bool sleeping_prematurely(pg_data_t *pgdat, int order, long remaining, + int classzone_idx) +{ + int i; + unsigned long balanced = 0; + bool all_zones_ok = true; + + /* If a direct reclaimer woke kswapd within HZ/10, it's premature */ + if (remaining) + return true; + + /* Check the watermark levels */ + for (i = 0; i <= classzone_idx; i++) { + struct zone *zone = pgdat->node_zones + i; + + if (!populated_zone(zone)) + continue; + + /* + * balance_pgdat() skips over all_unreclaimable after + * DEF_PRIORITY. Effectively, it considers them balanced so + * they must be considered balanced here as well if kswapd + * is to sleep + */ + if (zone->all_unreclaimable) { + balanced += zone->present_pages; + continue; + } + + if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone), + i, 0)) + all_zones_ok = false; + else + balanced += zone->present_pages; + } + + /* + * For high-order requests, the balanced zones must contain at least + * 25% of the nodes pages for kswapd to sleep. For order-0, all zones + * must be balanced + */ + if (order) + return !pgdat_balanced(pgdat, balanced, classzone_idx); + else + return !all_zones_ok; +} + +/* + * For kswapd, balance_pgdat() will work across all this node's zones until + * they are all at high_wmark_pages(zone). + * + * Returns the final order kswapd was reclaiming at + * + * There is special handling here for zones which are full of pinned pages. + * This can happen if the pages are all mlocked, or if they are all used by + * device drivers (say, ZONE_DMA). Or if they are all in use by hugetlb. + * What we do is to detect the case where all pages in the zone have been + * scanned twice and there has been zero successful reclaim. Mark the zone as + * dead and from now on, only perform a short scan. Basically we're polling + * the zone for when the problem goes away. + * + * kswapd scans the zones in the highmem->normal->dma direction. It skips + * zones which have free_pages > high_wmark_pages(zone), but once a zone is + * found to have free_pages <= high_wmark_pages(zone), we scan that zone and the + * lower zones regardless of the number of free pages in the lower zones. This + * interoperates with the page allocator fallback scheme to ensure that aging + * of pages is balanced across the zones. + */ +static unsigned long balance_pgdat(pg_data_t *pgdat, int order, + int *classzone_idx) +{ + int all_zones_ok; + unsigned long balanced; + int priority; + int i; + int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ + unsigned long total_scanned; + struct reclaim_state *reclaim_state = current->reclaim_state; + unsigned long nr_soft_reclaimed; + unsigned long nr_soft_scanned; + struct scan_control sc = { + .gfp_mask = GFP_KERNEL, + .may_unmap = 1, + .may_swap = 1, + /* + * kswapd doesn't want to be bailed out while reclaim. because + * we want to put equal scanning pressure on each zone. + */ + .nr_to_reclaim = ULONG_MAX, + .swappiness = vm_swappiness, + .order = order, + .mem_cgroup = NULL, + }; + struct shrink_control shrink = { + .gfp_mask = sc.gfp_mask, + }; +loop_again: + total_scanned = 0; + sc.nr_reclaimed = 0; + sc.may_writepage = !laptop_mode; + count_vm_event(PAGEOUTRUN); + + for (priority = DEF_PRIORITY; priority >= 0; priority--) { + unsigned long lru_pages = 0; + int has_under_min_watermark_zone = 0; + + /* The swap token gets in the way of swapout... */ + if (!priority) + disable_swap_token(NULL); + + all_zones_ok = 1; + balanced = 0; + + /* + * Scan in the highmem->dma direction for the highest + * zone which needs scanning + */ + for (i = pgdat->nr_zones - 1; i >= 0; i--) { + struct zone *zone = pgdat->node_zones + i; + + if (!populated_zone(zone)) + continue; + + if (zone->all_unreclaimable && priority != DEF_PRIORITY) + continue; + + /* + * Do some background aging of the anon list, to give + * pages a chance to be referenced before reclaiming. + */ + if (inactive_anon_is_low(zone, &sc)) + shrink_active_list(SWAP_CLUSTER_MAX, zone, + &sc, priority, 0); + + if (!zone_watermark_ok_safe(zone, order, + high_wmark_pages(zone), 0, 0)) { + end_zone = i; + break; + } + } + if (i < 0) + goto out; + + for (i = 0; i <= end_zone; i++) { + struct zone *zone = pgdat->node_zones + i; + + lru_pages += zone_reclaimable_pages(zone); + } + + /* + * Now scan the zone in the dma->highmem direction, stopping + * at the last zone which needs scanning. + * + * We do this because the page allocator works in the opposite + * direction. This prevents the page allocator from allocating + * pages behind kswapd's direction of progress, which would + * cause too much scanning of the lower zones. + */ + for (i = 0; i <= end_zone; i++) { + struct zone *zone = pgdat->node_zones + i; + int nr_slab; + unsigned long balance_gap; + + if (!populated_zone(zone)) + continue; + + if (zone->all_unreclaimable && priority != DEF_PRIORITY) + continue; + + sc.nr_scanned = 0; + + nr_soft_scanned = 0; + /* + * Call soft limit reclaim before calling shrink_zone. + */ + nr_soft_reclaimed = mem_cgroup_soft_limit_reclaim(zone, + order, sc.gfp_mask, + &nr_soft_scanned); + sc.nr_reclaimed += nr_soft_reclaimed; + total_scanned += nr_soft_scanned; + + /* + * We put equal pressure on every zone, unless + * one zone has way too many pages free + * already. The "too many pages" is defined + * as the high wmark plus a "gap" where the + * gap is either the low watermark or 1% + * of the zone, whichever is smaller. + */ + balance_gap = min(low_wmark_pages(zone), + (zone->present_pages + + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / + KSWAPD_ZONE_BALANCE_GAP_RATIO); + if (!zone_watermark_ok_safe(zone, order, + high_wmark_pages(zone) + balance_gap, + end_zone, 0)) { + shrink_zone(priority, zone, &sc); + + reclaim_state->reclaimed_slab = 0; + nr_slab = shrink_slab(&shrink, sc.nr_scanned, lru_pages); + sc.nr_reclaimed += reclaim_state->reclaimed_slab; + total_scanned += sc.nr_scanned; + + if (nr_slab == 0 && !zone_reclaimable(zone)) + zone->all_unreclaimable = 1; + } + + /* + * If we've done a decent amount of scanning and + * the reclaim ratio is low, start doing writepage + * even in laptop mode + */ + if (total_scanned > SWAP_CLUSTER_MAX * 2 && + total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) + sc.may_writepage = 1; + + if (zone->all_unreclaimable) { + if (end_zone && end_zone == i) + end_zone--; + continue; + } + + if (!zone_watermark_ok_safe(zone, order, + high_wmark_pages(zone), end_zone, 0)) { + all_zones_ok = 0; + /* + * We are still under min water mark. This + * means that we have a GFP_ATOMIC allocation + * failure risk. Hurry up! + */ + if (!zone_watermark_ok_safe(zone, order, + min_wmark_pages(zone), end_zone, 0)) + has_under_min_watermark_zone = 1; + } else { + /* + * If a zone reaches its high watermark, + * consider it to be no longer congested. It's + * possible there are dirty pages backed by + * congested BDIs but as pressure is relieved, + * spectulatively avoid congestion waits + */ + zone_clear_flag(zone, ZONE_CONGESTED); + if (i <= *classzone_idx) + balanced += zone->present_pages; + } + + } + if (all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx))) + break; /* kswapd: all done */ + /* + * OK, kswapd is getting into trouble. Take a nap, then take + * another pass across the zones. + */ + if (total_scanned && (priority < DEF_PRIORITY - 2)) { + if (has_under_min_watermark_zone) + count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT); + else + congestion_wait(BLK_RW_ASYNC, HZ/10); + } + + /* + * We do this so kswapd doesn't build up large priorities for + * example when it is freeing in parallel with allocators. It + * matches the direct reclaim path behaviour in terms of impact + * on zone->*_priority. + */ + if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX) + break; + } +out: + + /* + * order-0: All zones must meet high watermark for a balanced node + * high-order: Balanced zones must make up at least 25% of the node + * for the node to be balanced + */ + if (!(all_zones_ok || (order && pgdat_balanced(pgdat, balanced, *classzone_idx)))) { + cond_resched(); + + try_to_freeze(); + + /* + * Fragmentation may mean that the system cannot be + * rebalanced for high-order allocations in all zones. + * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX, + * it means the zones have been fully scanned and are still + * not balanced. For high-order allocations, there is + * little point trying all over again as kswapd may + * infinite loop. + * + * Instead, recheck all watermarks at order-0 as they + * are the most important. If watermarks are ok, kswapd will go + * back to sleep. High-order users can still perform direct + * reclaim if they wish. + */ + if (sc.nr_reclaimed < SWAP_CLUSTER_MAX) + order = sc.order = 0; + + goto loop_again; + } + + /* + * If kswapd was reclaiming at a higher order, it has the option of + * sleeping without all zones being balanced. Before it does, it must + * ensure that the watermarks for order-0 on *all* zones are met and + * that the congestion flags are cleared. The congestion flag must + * be cleared as kswapd is the only mechanism that clears the flag + * and it is potentially going to sleep here. + */ + if (order) { + for (i = 0; i <= end_zone; i++) { + struct zone *zone = pgdat->node_zones + i; + + if (!populated_zone(zone)) + continue; + + if (zone->all_unreclaimable && priority != DEF_PRIORITY) + continue; + + /* Confirm the zone is balanced for order-0 */ + if (!zone_watermark_ok(zone, 0, + high_wmark_pages(zone), 0, 0)) { + order = sc.order = 0; + goto loop_again; + } + + /* If balanced, clear the congested flag */ + zone_clear_flag(zone, ZONE_CONGESTED); + } + } + + /* + * Return the order we were reclaiming at so sleeping_prematurely() + * makes a decision on the order we were last reclaiming at. However, + * if another caller entered the allocator slow path while kswapd + * was awake, order will remain at the higher level + */ + *classzone_idx = end_zone; + return order; +} + +static void kswapd_try_to_sleep(pg_data_t *pgdat, int order, int classzone_idx) +{ + long remaining = 0; + DEFINE_WAIT(wait); + + if (freezing(current) || kthread_should_stop()) + return; + + prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); + + /* Try to sleep for a short interval */ + if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { + remaining = schedule_timeout(HZ/10); + finish_wait(&pgdat->kswapd_wait, &wait); + prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); + } + + /* + * After a short sleep, check if it was a premature sleep. If not, then + * go fully to sleep until explicitly woken up. + */ + if (!sleeping_prematurely(pgdat, order, remaining, classzone_idx)) { + trace_mm_vmscan_kswapd_sleep(pgdat->node_id); + + /* + * vmstat counters are not perfectly accurate and the estimated + * value for counters such as NR_FREE_PAGES can deviate from the + * true value by nr_online_cpus * threshold. To avoid the zone + * watermarks being breached while under pressure, we reduce the + * per-cpu vmstat threshold while kswapd is awake and restore + * them before going back to sleep. + */ + set_pgdat_percpu_threshold(pgdat, calculate_normal_threshold); + schedule(); + set_pgdat_percpu_threshold(pgdat, calculate_pressure_threshold); + } else { + if (remaining) + count_vm_event(KSWAPD_LOW_WMARK_HIT_QUICKLY); + else + count_vm_event(KSWAPD_HIGH_WMARK_HIT_QUICKLY); + } + finish_wait(&pgdat->kswapd_wait, &wait); +} + +/* + * The background pageout daemon, started as a kernel thread + * from the init process. + * + * This basically trickles out pages so that we have _some_ + * free memory available even if there is no other activity + * that frees anything up. This is needed for things like routing + * etc, where we otherwise might have all activity going on in + * asynchronous contexts that cannot page things out. + * + * If there are applications that are active memory-allocators + * (most normal use), this basically shouldn't matter. + */ +static int kswapd(void *p) +{ + unsigned long order, new_order; + int classzone_idx, new_classzone_idx; + pg_data_t *pgdat = (pg_data_t*)p; + struct task_struct *tsk = current; + + struct reclaim_state reclaim_state = { + .reclaimed_slab = 0, + }; + const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id); + + lockdep_set_current_reclaim_state(GFP_KERNEL); + + if (!cpumask_empty(cpumask)) + set_cpus_allowed_ptr(tsk, cpumask); + current->reclaim_state = &reclaim_state; + + /* + * Tell the memory management that we're a "memory allocator", + * and that if we need more memory we should get access to it + * regardless (see "__alloc_pages()"). "kswapd" should + * never get caught in the normal page freeing logic. + * + * (Kswapd normally doesn't need memory anyway, but sometimes + * you need a small amount of memory in order to be able to + * page out something else, and this flag essentially protects + * us from recursively trying to free more memory as we're + * trying to free the first piece of memory in the first place). + */ + tsk->flags |= PF_MEMALLOC | PF_SWAPWRITE | PF_KSWAPD; + set_freezable(); + + order = new_order = 0; + classzone_idx = new_classzone_idx = pgdat->nr_zones - 1; + for ( ; ; ) { + int ret; + + /* + * If the last balance_pgdat was unsuccessful it's unlikely a + * new request of a similar or harder type will succeed soon + * so consider going to sleep on the basis we reclaimed at + */ + if (classzone_idx >= new_classzone_idx && order == new_order) { + new_order = pgdat->kswapd_max_order; + new_classzone_idx = pgdat->classzone_idx; + pgdat->kswapd_max_order = 0; + pgdat->classzone_idx = pgdat->nr_zones - 1; + } + + if (order < new_order || classzone_idx > new_classzone_idx) { + /* + * Don't sleep if someone wants a larger 'order' + * allocation or has tigher zone constraints + */ + order = new_order; + classzone_idx = new_classzone_idx; + } else { + kswapd_try_to_sleep(pgdat, order, classzone_idx); + order = pgdat->kswapd_max_order; + classzone_idx = pgdat->classzone_idx; + pgdat->kswapd_max_order = 0; + pgdat->classzone_idx = pgdat->nr_zones - 1; + } + + ret = try_to_freeze(); + if (kthread_should_stop()) + break; + + /* + * We can speed up thawing tasks if we don't call balance_pgdat + * after returning from the refrigerator + */ + if (!ret) { + trace_mm_vmscan_kswapd_wake(pgdat->node_id, order); + order = balance_pgdat(pgdat, order, &classzone_idx); + } + } + return 0; +} + +/* + * A zone is low on free memory, so wake its kswapd task to service it. + */ +void wakeup_kswapd(struct zone *zone, int order, enum zone_type classzone_idx) +{ + pg_data_t *pgdat; + + if (!populated_zone(zone)) + return; + + if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) + return; + pgdat = zone->zone_pgdat; + if (pgdat->kswapd_max_order < order) { + pgdat->kswapd_max_order = order; + pgdat->classzone_idx = min(pgdat->classzone_idx, classzone_idx); + } + if (!waitqueue_active(&pgdat->kswapd_wait)) + return; + if (zone_watermark_ok_safe(zone, order, low_wmark_pages(zone), 0, 0)) + return; + + trace_mm_vmscan_wakeup_kswapd(pgdat->node_id, zone_idx(zone), order); + wake_up_interruptible(&pgdat->kswapd_wait); +} + +/* + * The reclaimable count would be mostly accurate. + * The less reclaimable pages may be + * - mlocked pages, which will be moved to unevictable list when encountered + * - mapped pages, which may require several travels to be reclaimed + * - dirty pages, which is not "instantly" reclaimable + */ +unsigned long global_reclaimable_pages(void) +{ + int nr; + + nr = global_page_state(NR_ACTIVE_FILE) + + global_page_state(NR_INACTIVE_FILE); + + if (nr_swap_pages > 0) + nr += global_page_state(NR_ACTIVE_ANON) + + global_page_state(NR_INACTIVE_ANON); + + return nr; +} + +unsigned long zone_reclaimable_pages(struct zone *zone) +{ + int nr; + + nr = zone_page_state(zone, NR_ACTIVE_FILE) + + zone_page_state(zone, NR_INACTIVE_FILE); + + if (nr_swap_pages > 0) + nr += zone_page_state(zone, NR_ACTIVE_ANON) + + zone_page_state(zone, NR_INACTIVE_ANON); + + return nr; +} + +#ifdef CONFIG_HIBERNATION +/* + * Try to free `nr_to_reclaim' of memory, system-wide, and return the number of + * freed pages. + * + * Rather than trying to age LRUs the aim is to preserve the overall + * LRU order by reclaiming preferentially + * inactive > active > active referenced > active mapped + */ +unsigned long shrink_all_memory(unsigned long nr_to_reclaim) +{ + struct reclaim_state reclaim_state; + struct scan_control sc = { + .gfp_mask = GFP_HIGHUSER_MOVABLE, + .may_swap = 1, + .may_unmap = 1, + .may_writepage = 1, + .nr_to_reclaim = nr_to_reclaim, + .hibernation_mode = 1, + .swappiness = vm_swappiness, + .order = 0, + }; + struct shrink_control shrink = { + .gfp_mask = sc.gfp_mask, + }; + struct zonelist *zonelist = node_zonelist(numa_node_id(), sc.gfp_mask); + struct task_struct *p = current; + unsigned long nr_reclaimed; + + p->flags |= PF_MEMALLOC; + lockdep_set_current_reclaim_state(sc.gfp_mask); + reclaim_state.reclaimed_slab = 0; + p->reclaim_state = &reclaim_state; + + nr_reclaimed = do_try_to_free_pages(zonelist, &sc, &shrink); + + p->reclaim_state = NULL; + lockdep_clear_current_reclaim_state(); + p->flags &= ~PF_MEMALLOC; + + return nr_reclaimed; +} +#endif /* CONFIG_HIBERNATION */ + +/* It's optimal to keep kswapds 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 __devinit cpu_callback(struct notifier_block *nfb, + unsigned long action, void *hcpu) +{ + int nid; + + if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { + for_each_node_state(nid, N_HIGH_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 */ + set_cpus_allowed_ptr(pgdat->kswapd, mask); + } + } + return NOTIFY_OK; +} + +/* + * This kswapd start function will be called by init and node-hot-add. + * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. + */ +int kswapd_run(int nid) +{ + pg_data_t *pgdat = NODE_DATA(nid); + int ret = 0; + + if (pgdat->kswapd) + return 0; + + pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); + if (IS_ERR(pgdat->kswapd)) { + /* failure at boot is fatal */ + BUG_ON(system_state == SYSTEM_BOOTING); + printk("Failed to start kswapd on node %d\n",nid); + ret = -1; + } + return ret; +} + +/* + * Called by memory hotplug when all memory in a node is offlined. + */ +void kswapd_stop(int nid) +{ + struct task_struct *kswapd = NODE_DATA(nid)->kswapd; + + if (kswapd) + kthread_stop(kswapd); +} + +static int __init kswapd_init(void) +{ + int nid; + + swap_setup(); + for_each_node_state(nid, N_HIGH_MEMORY) + kswapd_run(nid); + hotcpu_notifier(cpu_callback, 0); + return 0; +} + +module_init(kswapd_init) + +#ifdef CONFIG_NUMA +/* + * Zone reclaim mode + * + * If non-zero call zone_reclaim when the number of free pages falls below + * the watermarks. + */ +int zone_reclaim_mode __read_mostly; + +#define RECLAIM_OFF 0 +#define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ +#define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ +#define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ + +/* + * Priority for ZONE_RECLAIM. This determines the fraction of pages + * of a node considered for each zone_reclaim. 4 scans 1/16th of + * a zone. + */ +#define ZONE_RECLAIM_PRIORITY 4 + +/* + * Percentage of pages in a zone that must be unmapped for zone_reclaim to + * occur. + */ +int sysctl_min_unmapped_ratio = 1; + +/* + * If the number of slab pages in a zone grows beyond this percentage then + * slab reclaim needs to occur. + */ +int sysctl_min_slab_ratio = 5; + +static inline unsigned long zone_unmapped_file_pages(struct zone *zone) +{ + unsigned long file_mapped = zone_page_state(zone, NR_FILE_MAPPED); + unsigned long file_lru = zone_page_state(zone, NR_INACTIVE_FILE) + + zone_page_state(zone, NR_ACTIVE_FILE); + + /* + * It's possible for there to be more file mapped pages than + * accounted for by the pages on the file LRU lists because + * tmpfs pages accounted for as ANON can also be FILE_MAPPED + */ + return (file_lru > file_mapped) ? (file_lru - file_mapped) : 0; +} + +/* Work out how many page cache pages we can reclaim in this reclaim_mode */ +static long zone_pagecache_reclaimable(struct zone *zone) +{ + long nr_pagecache_reclaimable; + long delta = 0; + + /* + * If RECLAIM_SWAP is set, then all file pages are considered + * potentially reclaimable. Otherwise, we have to worry about + * pages like swapcache and zone_unmapped_file_pages() provides + * a better estimate + */ + if (zone_reclaim_mode & RECLAIM_SWAP) + nr_pagecache_reclaimable = zone_page_state(zone, NR_FILE_PAGES); + else + nr_pagecache_reclaimable = zone_unmapped_file_pages(zone); + + /* If we can't clean pages, remove dirty pages from consideration */ + if (!(zone_reclaim_mode & RECLAIM_WRITE)) + delta += zone_page_state(zone, NR_FILE_DIRTY); + + /* Watch for any possible underflows due to delta */ + if (unlikely(delta > nr_pagecache_reclaimable)) + delta = nr_pagecache_reclaimable; + + return nr_pagecache_reclaimable - delta; +} + +/* + * Try to free up some pages from this zone through reclaim. + */ +static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) +{ + /* Minimum pages needed in order to stay on node */ + const unsigned long nr_pages = 1 << order; + struct task_struct *p = current; + struct reclaim_state reclaim_state; + int priority; + struct scan_control sc = { + .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), + .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP), + .may_swap = 1, + .nr_to_reclaim = max_t(unsigned long, nr_pages, + SWAP_CLUSTER_MAX), + .gfp_mask = gfp_mask, + .swappiness = vm_swappiness, + .order = order, + }; + struct shrink_control shrink = { + .gfp_mask = sc.gfp_mask, + }; + unsigned long nr_slab_pages0, nr_slab_pages1; + + cond_resched(); + /* + * We need to be able to allocate from the reserves for RECLAIM_SWAP + * and we also need to be able to write out pages for RECLAIM_WRITE + * and RECLAIM_SWAP. + */ + p->flags |= PF_MEMALLOC | PF_SWAPWRITE; + lockdep_set_current_reclaim_state(gfp_mask); + reclaim_state.reclaimed_slab = 0; + p->reclaim_state = &reclaim_state; + + if (zone_pagecache_reclaimable(zone) > zone->min_unmapped_pages) { + /* + * Free memory by calling shrink zone with increasing + * priorities until we have enough memory freed. + */ + priority = ZONE_RECLAIM_PRIORITY; + do { + shrink_zone(priority, zone, &sc); + priority--; + } while (priority >= 0 && sc.nr_reclaimed < nr_pages); + } + + nr_slab_pages0 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); + if (nr_slab_pages0 > zone->min_slab_pages) { + /* + * shrink_slab() does not currently allow us to determine how + * many pages were freed in this zone. So we take the current + * number of slab pages and shake the slab until it is reduced + * by the same nr_pages that we used for reclaiming unmapped + * pages. + * + * Note that shrink_slab will free memory on all zones and may + * take a long time. + */ + for (;;) { + unsigned long lru_pages = zone_reclaimable_pages(zone); + + /* No reclaimable slab or very low memory pressure */ + if (!shrink_slab(&shrink, sc.nr_scanned, lru_pages)) + break; + + /* Freed enough memory */ + nr_slab_pages1 = zone_page_state(zone, + NR_SLAB_RECLAIMABLE); + if (nr_slab_pages1 + nr_pages <= nr_slab_pages0) + break; + } + + /* + * Update nr_reclaimed by the number of slab pages we + * reclaimed from this zone. + */ + nr_slab_pages1 = zone_page_state(zone, NR_SLAB_RECLAIMABLE); + if (nr_slab_pages1 < nr_slab_pages0) + sc.nr_reclaimed += nr_slab_pages0 - nr_slab_pages1; + } + + p->reclaim_state = NULL; + current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); + lockdep_clear_current_reclaim_state(); + return sc.nr_reclaimed >= nr_pages; +} + +int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) +{ + int node_id; + int ret; + + /* + * Zone reclaim reclaims unmapped file backed pages and + * slab pages if we are over the defined limits. + * + * A small portion of unmapped file backed pages is needed for + * file I/O otherwise pages read by file I/O will be immediately + * thrown out if the zone is overallocated. So we do not reclaim + * if less than a specified percentage of the zone is used by + * unmapped file backed pages. + */ + if (zone_pagecache_reclaimable(zone) <= zone->min_unmapped_pages && + zone_page_state(zone, NR_SLAB_RECLAIMABLE) <= zone->min_slab_pages) + return ZONE_RECLAIM_FULL; + + if (zone->all_unreclaimable) + return ZONE_RECLAIM_FULL; + + /* + * Do not scan if the allocation should not be delayed. + */ + if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) + return ZONE_RECLAIM_NOSCAN; + + /* + * Only run zone reclaim on the local zone or on zones that do not + * have associated processors. This will favor the local processor + * over remote processors and spread off node memory allocations + * as wide as possible. + */ + node_id = zone_to_nid(zone); + if (node_state(node_id, N_CPU) && node_id != numa_node_id()) + return ZONE_RECLAIM_NOSCAN; + + if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED)) + return ZONE_RECLAIM_NOSCAN; + + ret = __zone_reclaim(zone, gfp_mask, order); + zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); + + if (!ret) + count_vm_event(PGSCAN_ZONE_RECLAIM_FAILED); + + return ret; +} +#endif + +/* + * page_evictable - test whether a page is evictable + * @page: the page to test + * @vma: the VMA in which the page is or will be mapped, may be NULL + * + * Test whether page is evictable--i.e., should be placed on active/inactive + * lists vs unevictable list. The vma argument is !NULL when called from the + * fault path to determine how to instantate a new page. + * + * Reasons page might not be evictable: + * (1) page's mapping marked unevictable + * (2) page is part of an mlocked VMA + * + */ +int page_evictable(struct page *page, struct vm_area_struct *vma) +{ + + if (mapping_unevictable(page_mapping(page))) + return 0; + + if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page))) + return 0; + + return 1; +} + +/** + * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list + * @page: page to check evictability and move to appropriate lru list + * @zone: zone page is in + * + * Checks a page for evictability and moves the page to the appropriate + * zone lru list. + * + * Restrictions: zone->lru_lock must be held, page must be on LRU and must + * have PageUnevictable set. + */ +static void check_move_unevictable_page(struct page *page, struct zone *zone) +{ + VM_BUG_ON(PageActive(page)); + +retry: + ClearPageUnevictable(page); + if (page_evictable(page, NULL)) { + enum lru_list l = page_lru_base_type(page); + + __dec_zone_state(zone, NR_UNEVICTABLE); + list_move(&page->lru, &zone->lru[l].list); + mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l); + __inc_zone_state(zone, NR_INACTIVE_ANON + l); + __count_vm_event(UNEVICTABLE_PGRESCUED); + } else { + /* + * rotate unevictable list + */ + SetPageUnevictable(page); + list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list); + mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE); + if (page_evictable(page, NULL)) + goto retry; + } +} + +/** + * scan_mapping_unevictable_pages - scan an address space for evictable pages + * @mapping: struct address_space to scan for evictable pages + * + * Scan all pages in mapping. Check unevictable pages for + * evictability and move them to the appropriate zone lru list. + */ +void scan_mapping_unevictable_pages(struct address_space *mapping) +{ + pgoff_t next = 0; + pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >> + PAGE_CACHE_SHIFT; + struct zone *zone; + struct pagevec pvec; + + if (mapping->nrpages == 0) + return; + + pagevec_init(&pvec, 0); + while (next < end && + pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { + int i; + int pg_scanned = 0; + + zone = NULL; + + for (i = 0; i < pagevec_count(&pvec); i++) { + struct page *page = pvec.pages[i]; + pgoff_t page_index = page->index; + struct zone *pagezone = page_zone(page); + + pg_scanned++; + if (page_index > next) + next = page_index; + next++; + + if (pagezone != zone) { + if (zone) + spin_unlock_irq(&zone->lru_lock); + zone = pagezone; + spin_lock_irq(&zone->lru_lock); + } + + if (PageLRU(page) && PageUnevictable(page)) + check_move_unevictable_page(page, zone); + } + if (zone) + spin_unlock_irq(&zone->lru_lock); + pagevec_release(&pvec); + + count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned); + } + +} + +/** + * scan_zone_unevictable_pages - check unevictable list for evictable pages + * @zone - zone of which to scan the unevictable list + * + * Scan @zone's unevictable LRU lists to check for pages that have become + * evictable. Move those that have to @zone's inactive list where they + * become candidates for reclaim, unless shrink_inactive_zone() decides + * to reactivate them. Pages that are still unevictable are rotated + * back onto @zone's unevictable list. + */ +#define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */ +static void scan_zone_unevictable_pages(struct zone *zone) +{ + struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list; + unsigned long scan; + unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE); + + while (nr_to_scan > 0) { + unsigned long batch_size = min(nr_to_scan, + SCAN_UNEVICTABLE_BATCH_SIZE); + + spin_lock_irq(&zone->lru_lock); + for (scan = 0; scan < batch_size; scan++) { + struct page *page = lru_to_page(l_unevictable); + + if (!trylock_page(page)) + continue; + + prefetchw_prev_lru_page(page, l_unevictable, flags); + + if (likely(PageLRU(page) && PageUnevictable(page))) + check_move_unevictable_page(page, zone); + + unlock_page(page); + } + spin_unlock_irq(&zone->lru_lock); + + nr_to_scan -= batch_size; + } +} + + +/** + * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages + * + * A really big hammer: scan all zones' unevictable LRU lists to check for + * pages that have become evictable. Move those back to the zones' + * inactive list where they become candidates for reclaim. + * This occurs when, e.g., we have unswappable pages on the unevictable lists, + * and we add swap to the system. As such, it runs in the context of a task + * that has possibly/probably made some previously unevictable pages + * evictable. + */ +static void scan_all_zones_unevictable_pages(void) +{ + struct zone *zone; + + for_each_zone(zone) { + scan_zone_unevictable_pages(zone); + } +} + +/* + * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of + * all nodes' unevictable lists for evictable pages + */ +unsigned long scan_unevictable_pages; + +int scan_unevictable_handler(struct ctl_table *table, int write, + void __user *buffer, + size_t *length, loff_t *ppos) +{ + proc_doulongvec_minmax(table, write, buffer, length, ppos); + + if (write && *(unsigned long *)table->data) + scan_all_zones_unevictable_pages(); + + scan_unevictable_pages = 0; + return 0; +} + +#ifdef CONFIG_NUMA +/* + * per node 'scan_unevictable_pages' attribute. On demand re-scan of + * a specified node's per zone unevictable lists for evictable pages. + */ + +static ssize_t read_scan_unevictable_node(struct sys_device *dev, + struct sysdev_attribute *attr, + char *buf) +{ + return sprintf(buf, "0\n"); /* always zero; should fit... */ +} + +static ssize_t write_scan_unevictable_node(struct sys_device *dev, + struct sysdev_attribute *attr, + const char *buf, size_t count) +{ + struct zone *node_zones = NODE_DATA(dev->id)->node_zones; + struct zone *zone; + unsigned long res; + unsigned long req = strict_strtoul(buf, 10, &res); + + if (!req) + return 1; /* zero is no-op */ + + for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) { + if (!populated_zone(zone)) + continue; + scan_zone_unevictable_pages(zone); + } + return 1; +} + + +static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR, + read_scan_unevictable_node, + write_scan_unevictable_node); + +int scan_unevictable_register_node(struct node *node) +{ + return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages); +} + +void scan_unevictable_unregister_node(struct node *node) +{ + sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages); +} +#endif |