| /* |
| * 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/vmpressure.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/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> |
| |
| 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 order; |
| |
| /* Scan (total_size >> priority) pages at once */ |
| int priority; |
| |
| /* |
| * The memory cgroup that hit its limit and as a result is the |
| * primary target of this reclaim invocation. |
| */ |
| struct mem_cgroup *target_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; |
| unsigned 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_MEMCG |
| static bool global_reclaim(struct scan_control *sc) |
| { |
| return !sc->target_mem_cgroup; |
| } |
| #else |
| static bool global_reclaim(struct scan_control *sc) |
| { |
| return true; |
| } |
| #endif |
| |
| static unsigned long get_lru_size(struct lruvec *lruvec, enum lru_list lru) |
| { |
| if (!mem_cgroup_disabled()) |
| return mem_cgroup_get_lru_size(lruvec, lru); |
| |
| return zone_page_state(lruvec_zone(lruvec), NR_LRU_BASE + lru); |
| } |
| |
| /* |
| * Add a shrinker callback to be called from the vm |
| */ |
| void register_shrinker(struct shrinker *shrinker) |
| { |
| atomic_long_set(&shrinker->nr_in_batch, 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; |
| long total_scan; |
| long max_pass; |
| int shrink_ret = 0; |
| long nr; |
| long new_nr; |
| long batch_size = shrinker->batch ? shrinker->batch |
| : SHRINK_BATCH; |
| |
| max_pass = do_shrinker_shrink(shrinker, shrink, 0); |
| if (max_pass <= 0) |
| continue; |
| |
| /* |
| * copy the current shrinker scan count into a local variable |
| * and zero it so that other concurrent shrinker invocations |
| * don't also do this scanning work. |
| */ |
| nr = atomic_long_xchg(&shrinker->nr_in_batch, 0); |
| |
| total_scan = nr; |
| delta = (4 * nr_pages_scanned) / shrinker->seeks; |
| delta *= max_pass; |
| do_div(delta, lru_pages + 1); |
| total_scan += delta; |
| if (total_scan < 0) { |
| printk(KERN_ERR "shrink_slab: %pF negative objects to " |
| "delete nr=%ld\n", |
| shrinker->shrink, total_scan); |
| total_scan = max_pass; |
| } |
| |
| /* |
| * We need to avoid excessive windup on filesystem shrinkers |
| * due to large numbers of GFP_NOFS allocations causing the |
| * shrinkers to return -1 all the time. This results in a large |
| * nr being built up so when a shrink that can do some work |
| * comes along it empties the entire cache due to nr >>> |
| * max_pass. This is bad for sustaining a working set in |
| * memory. |
| * |
| * Hence only allow the shrinker to scan the entire cache when |
| * a large delta change is calculated directly. |
| */ |
| if (delta < max_pass / 4) |
| total_scan = min(total_scan, max_pass / 2); |
| |
| /* |
| * Avoid risking looping forever due to too large nr value: |
| * never try to free more than twice the estimate number of |
| * freeable entries. |
| */ |
| if (total_scan > max_pass * 2) |
| total_scan = max_pass * 2; |
| |
| trace_mm_shrink_slab_start(shrinker, shrink, nr, |
| nr_pages_scanned, lru_pages, |
| max_pass, delta, total_scan); |
| |
| while (total_scan >= batch_size) { |
| int nr_before; |
| |
| nr_before = do_shrinker_shrink(shrinker, shrink, 0); |
| shrink_ret = do_shrinker_shrink(shrinker, shrink, |
| batch_size); |
| if (shrink_ret == -1) |
| break; |
| if (shrink_ret < nr_before) |
| ret += nr_before - shrink_ret; |
| count_vm_events(SLABS_SCANNED, batch_size); |
| total_scan -= batch_size; |
| |
| cond_resched(); |
| } |
| |
| /* |
| * move the unused scan count back into the shrinker in a |
| * manner that handles concurrent updates. If we exhausted the |
| * scan, there is no need to do an update. |
| */ |
| if (total_scan > 0) |
| new_nr = atomic_long_add_return(total_scan, |
| &shrinker->nr_in_batch); |
| else |
| new_nr = atomic_long_read(&shrinker->nr_in_batch); |
| |
| trace_mm_shrink_slab_end(shrinker, shrink_ret, nr, new_nr); |
| } |
| up_read(&shrinker_rwsem); |
| out: |
| cond_resched(); |
| return ret; |
| } |
| |
| 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; |
| 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; |
| } |
| |
| if (!PageWriteback(page)) { |
| /* synchronous write or broken a_ops? */ |
| ClearPageReclaim(page); |
| } |
| trace_mm_vmscan_writepage(page, trace_reclaim_flags(page)); |
| 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)) { |
| /* |
| * 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 or AS_UNEVICTABLE clearing |
| * (page is unlocked) make sure that if the other thread |
| * does not observe our setting of PG_lru and fails |
| * isolation/check_move_unevictable_pages, |
| * we see PG_mlocked/AS_UNEVICTABLE cleared below and move |
| * the page back to the evictable list. |
| * |
| * The other side is TestClearPageMlocked() or shmem_lock(). |
| */ |
| 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)) { |
| 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->target_mem_cgroup, |
| &vm_flags); |
| referenced_page = TestClearPageReferenced(page); |
| |
| /* |
| * 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 || referenced_ptes > 1) |
| return PAGEREF_ACTIVATE; |
| |
| /* |
| * Activate file-backed executable pages after first usage. |
| */ |
| if (vm_flags & VM_EXEC) |
| 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; |
| } |
| |
| /* Check if a page is dirty or under writeback */ |
| static void page_check_dirty_writeback(struct page *page, |
| bool *dirty, bool *writeback) |
| { |
| /* |
| * Anonymous pages are not handled by flushers and must be written |
| * from reclaim context. Do not stall reclaim based on them |
| */ |
| if (!page_is_file_cache(page)) { |
| *dirty = false; |
| *writeback = false; |
| return; |
| } |
| |
| /* By default assume that the page flags are accurate */ |
| *dirty = PageDirty(page); |
| *writeback = PageWriteback(page); |
| } |
| |
| /* |
| * 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, |
| enum ttu_flags ttu_flags, |
| unsigned long *ret_nr_dirty, |
| unsigned long *ret_nr_unqueued_dirty, |
| unsigned long *ret_nr_congested, |
| unsigned long *ret_nr_writeback, |
| unsigned long *ret_nr_immediate, |
| bool force_reclaim) |
| { |
| LIST_HEAD(ret_pages); |
| LIST_HEAD(free_pages); |
| int pgactivate = 0; |
| unsigned long nr_unqueued_dirty = 0; |
| unsigned long nr_dirty = 0; |
| unsigned long nr_congested = 0; |
| unsigned long nr_reclaimed = 0; |
| unsigned long nr_writeback = 0; |
| unsigned long nr_immediate = 0; |
| |
| cond_resched(); |
| |
| mem_cgroup_uncharge_start(); |
| while (!list_empty(page_list)) { |
| struct address_space *mapping; |
| struct page *page; |
| int may_enter_fs; |
| enum page_references references = PAGEREF_RECLAIM_CLEAN; |
| bool dirty, writeback; |
| |
| 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))) |
| 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)); |
| |
| /* |
| * The number of dirty pages determines if a zone is marked |
| * reclaim_congested which affects wait_iff_congested. kswapd |
| * will stall and start writing pages if the tail of the LRU |
| * is all dirty unqueued pages. |
| */ |
| page_check_dirty_writeback(page, &dirty, &writeback); |
| if (dirty || writeback) |
| nr_dirty++; |
| |
| if (dirty && !writeback) |
| nr_unqueued_dirty++; |
| |
| /* |
| * Treat this page as congested if the underlying BDI is or if |
| * pages are cycling through the LRU so quickly that the |
| * pages marked for immediate reclaim are making it to the |
| * end of the LRU a second time. |
| */ |
| mapping = page_mapping(page); |
| if ((mapping && bdi_write_congested(mapping->backing_dev_info)) || |
| (writeback && PageReclaim(page))) |
| nr_congested++; |
| |
| /* |
| * If a page at the tail of the LRU is under writeback, there |
| * are three cases to consider. |
| * |
| * 1) If reclaim is encountering an excessive number of pages |
| * under writeback and this page is both under writeback and |
| * PageReclaim then it indicates that pages are being queued |
| * for IO but are being recycled through the LRU before the |
| * IO can complete. Waiting on the page itself risks an |
| * indefinite stall if it is impossible to writeback the |
| * page due to IO error or disconnected storage so instead |
| * note that the LRU is being scanned too quickly and the |
| * caller can stall after page list has been processed. |
| * |
| * 2) Global reclaim encounters a page, memcg encounters a |
| * page that is not marked for immediate reclaim or |
| * the caller does not have __GFP_IO. In this case mark |
| * the page for immediate reclaim and continue scanning. |
| * |
| * __GFP_IO is checked because a loop driver thread might |
| * enter reclaim, and deadlock if it waits on a page for |
| * which it is needed to do the write (loop masks off |
| * __GFP_IO|__GFP_FS for this reason); but more thought |
| * would probably show more reasons. |
| * |
| * Don't require __GFP_FS, since we're not going into the |
| * FS, just waiting on its writeback completion. Worryingly, |
| * ext4 gfs2 and xfs allocate pages with |
| * grab_cache_page_write_begin(,,AOP_FLAG_NOFS), so testing |
| * may_enter_fs here is liable to OOM on them. |
| * |
| * 3) memcg encounters a page that is not already marked |
| * PageReclaim. memcg does not have any dirty pages |
| * throttling so we could easily OOM just because too many |
| * pages are in writeback and there is nothing else to |
| * reclaim. Wait for the writeback to complete. |
| */ |
| if (PageWriteback(page)) { |
| /* Case 1 above */ |
| if (current_is_kswapd() && |
| PageReclaim(page) && |
| zone_is_reclaim_writeback(zone)) { |
| nr_immediate++; |
| goto keep_locked; |
| |
| /* Case 2 above */ |
| } else if (global_reclaim(sc) || |
| !PageReclaim(page) || !(sc->gfp_mask & __GFP_IO)) { |
| /* |
| * This is slightly racy - end_page_writeback() |
| * might have just cleared PageReclaim, then |
| * setting PageReclaim here end up interpreted |
| * as PageReadahead - but that does not matter |
| * enough to care. What we do want is for this |
| * page to have PageReclaim set next time memcg |
| * reclaim reaches the tests above, so it will |
| * then wait_on_page_writeback() to avoid OOM; |
| * and it's also appropriate in global reclaim. |
| */ |
| SetPageReclaim(page); |
| nr_writeback++; |
| |
| goto keep_locked; |
| |
| /* Case 3 above */ |
| } else { |
| wait_on_page_writeback(page); |
| } |
| } |
| |
| if (!force_reclaim) |
| 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, page_list)) |
| goto activate_locked; |
| may_enter_fs = 1; |
| |
| /* Adding to swap updated mapping */ |
| 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_flags)) { |
| 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)) { |
| /* |
| * Only kswapd can writeback filesystem pages to |
| * avoid risk of stack overflow but only writeback |
| * if many dirty pages have been encountered. |
| */ |
| if (page_is_file_cache(page) && |
| (!current_is_kswapd() || |
| !zone_is_reclaim_dirty(zone))) { |
| /* |
| * Immediately reclaim when written back. |
| * Similar in principal to deactivate_page() |
| * except we already have the page isolated |
| * and know it's dirty |
| */ |
| inc_zone_page_state(page, NR_VMSCAN_IMMEDIATE); |
| SetPageReclaim(page); |
| |
| goto keep_locked; |
| } |
| |
| 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: |
| goto keep_locked; |
| case PAGE_ACTIVATE: |
| goto activate_locked; |
| case PAGE_SUCCESS: |
| if (PageWriteback(page)) |
| goto keep; |
| 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); |
| 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: |
| list_add(&page->lru, &ret_pages); |
| VM_BUG_ON(PageLRU(page) || PageUnevictable(page)); |
| } |
| |
| free_hot_cold_page_list(&free_pages, 1); |
| |
| list_splice(&ret_pages, page_list); |
| count_vm_events(PGACTIVATE, pgactivate); |
| mem_cgroup_uncharge_end(); |
| *ret_nr_dirty += nr_dirty; |
| *ret_nr_congested += nr_congested; |
| *ret_nr_unqueued_dirty += nr_unqueued_dirty; |
| *ret_nr_writeback += nr_writeback; |
| *ret_nr_immediate += nr_immediate; |
| return nr_reclaimed; |
| } |
| |
| unsigned long reclaim_clean_pages_from_list(struct zone *zone, |
| struct list_head *page_list) |
| { |
| struct scan_control sc = { |
| .gfp_mask = GFP_KERNEL, |
| .priority = DEF_PRIORITY, |
| .may_unmap = 1, |
| }; |
| unsigned long ret, dummy1, dummy2, dummy3, dummy4, dummy5; |
| struct page *page, *next; |
| LIST_HEAD(clean_pages); |
| |
| list_for_each_entry_safe(page, next, page_list, lru) { |
| if (page_is_file_cache(page) && !PageDirty(page)) { |
| ClearPageActive(page); |
| list_move(&page->lru, &clean_pages); |
| } |
| } |
| |
| ret = shrink_page_list(&clean_pages, zone, &sc, |
| TTU_UNMAP|TTU_IGNORE_ACCESS, |
| &dummy1, &dummy2, &dummy3, &dummy4, &dummy5, true); |
| list_splice(&clean_pages, page_list); |
| __mod_zone_page_state(zone, NR_ISOLATED_FILE, -ret); |
| return ret; |
| } |
| |
| /* |
| * 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, isolate_mode_t mode) |
| { |
| int ret = -EINVAL; |
| |
| /* Only take pages on the LRU. */ |
| if (!PageLRU(page)) |
| return ret; |
| |
| /* Compaction should not handle unevictable pages but CMA can do so */ |
| if (PageUnevictable(page) && !(mode & ISOLATE_UNEVICTABLE)) |
| return ret; |
| |
| ret = -EBUSY; |
| |
| /* |
| * To minimise LRU disruption, the caller can indicate that it only |
| * wants to isolate pages it will be able to operate on without |
| * blocking - clean pages for the most part. |
| * |
| * ISOLATE_CLEAN means that only clean pages should be isolated. This |
| * is used by reclaim when it is cannot write to backing storage |
| * |
| * ISOLATE_ASYNC_MIGRATE is used to indicate that it only wants to pages |
| * that it is possible to migrate without blocking |
| */ |
| if (mode & (ISOLATE_CLEAN|ISOLATE_ASYNC_MIGRATE)) { |
| /* All the caller can do on PageWriteback is block */ |
| if (PageWriteback(page)) |
| return ret; |
| |
| if (PageDirty(page)) { |
| struct address_space *mapping; |
| |
| /* ISOLATE_CLEAN means only clean pages */ |
| if (mode & ISOLATE_CLEAN) |
| return ret; |
| |
| /* |
| * Only pages without mappings or that have a |
| * ->migratepage callback are possible to migrate |
| * without blocking |
| */ |
| mapping = page_mapping(page); |
| if (mapping && !mapping->a_ops->migratepage) |
| return ret; |
| } |
| } |
| |
| if ((mode & ISOLATE_UNMAPPED) && page_mapped(page)) |
| return ret; |
| |
| 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. |
| * @lruvec: The LRU vector to pull pages from. |
| * @dst: The temp list to put pages on to. |
| * @nr_scanned: The number of pages that were scanned. |
| * @sc: The scan_control struct for this reclaim session |
| * @mode: One of the LRU isolation modes |
| * @lru: LRU list id for isolating |
| * |
| * returns how many pages were moved onto *@dst. |
| */ |
| static unsigned long isolate_lru_pages(unsigned long nr_to_scan, |
| struct lruvec *lruvec, struct list_head *dst, |
| unsigned long *nr_scanned, struct scan_control *sc, |
| isolate_mode_t mode, enum lru_list lru) |
| { |
| struct list_head *src = &lruvec->lists[lru]; |
| unsigned long nr_taken = 0; |
| unsigned long scan; |
| |
| for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) { |
| struct page *page; |
| int nr_pages; |
| |
| page = lru_to_page(src); |
| prefetchw_prev_lru_page(page, src, flags); |
| |
| VM_BUG_ON(!PageLRU(page)); |
| |
| switch (__isolate_lru_page(page, mode)) { |
| case 0: |
| nr_pages = hpage_nr_pages(page); |
| mem_cgroup_update_lru_size(lruvec, lru, -nr_pages); |
| list_move(&page->lru, dst); |
| nr_taken += nr_pages; |
| break; |
| |
| case -EBUSY: |
| /* else it is being freed elsewhere */ |
| list_move(&page->lru, src); |
| continue; |
| |
| default: |
| BUG(); |
| } |
| } |
| |
| *nr_scanned = scan; |
| trace_mm_vmscan_lru_isolate(sc->order, nr_to_scan, scan, |
| nr_taken, mode, is_file_lru(lru)); |
| return nr_taken; |
| } |
| |
| /** |
| * 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); |
| struct lruvec *lruvec; |
| |
| spin_lock_irq(&zone->lru_lock); |
| lruvec = mem_cgroup_page_lruvec(page, zone); |
| if (PageLRU(page)) { |
| int lru = page_lru(page); |
| get_page(page); |
| ClearPageLRU(page); |
| del_page_from_lru_list(page, lruvec, lru); |
| ret = 0; |
| } |
| spin_unlock_irq(&zone->lru_lock); |
| } |
| return ret; |
| } |
| |
| /* |
| * A direct reclaimer may isolate SWAP_CLUSTER_MAX pages from the LRU list and |
| * then get resheduled. When there are massive number of tasks doing page |
| * allocation, such sleeping direct reclaimers may keep piling up on each CPU, |
| * the LRU list will go small and be scanned faster than necessary, leading to |
| * unnecessary swapping, thrashing and OOM. |
| */ |
| 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 (!global_reclaim(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); |
| } |
| |
| /* |
| * GFP_NOIO/GFP_NOFS callers are allowed to isolate more pages, so they |
| * won't get blocked by normal direct-reclaimers, forming a circular |
| * deadlock. |
| */ |
| if ((sc->gfp_mask & GFP_IOFS) == GFP_IOFS) |
| inactive >>= 3; |
| |
| return isolated > inactive; |
| } |
| |
| static noinline_for_stack void |
| putback_inactive_pages(struct lruvec *lruvec, struct list_head *page_list) |
| { |
| struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; |
| struct zone *zone = lruvec_zone(lruvec); |
| LIST_HEAD(pages_to_free); |
| |
| /* |
| * Put back any unfreeable pages. |
| */ |
| while (!list_empty(page_list)) { |
| struct page *page = lru_to_page(page_list); |
| int lru; |
| |
| VM_BUG_ON(PageLRU(page)); |
| list_del(&page->lru); |
| if (unlikely(!page_evictable(page))) { |
| spin_unlock_irq(&zone->lru_lock); |
| putback_lru_page(page); |
| spin_lock_irq(&zone->lru_lock); |
| continue; |
| } |
| |
| lruvec = mem_cgroup_page_lruvec(page, zone); |
| |
| SetPageLRU(page); |
| lru = page_lru(page); |
| add_page_to_lru_list(page, lruvec, 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 (put_page_testzero(page)) { |
| __ClearPageLRU(page); |
| __ClearPageActive(page); |
| del_page_from_lru_list(page, lruvec, lru); |
| |
| if (unlikely(PageCompound(page))) { |
| spin_unlock_irq(&zone->lru_lock); |
| (*get_compound_page_dtor(page))(page); |
| spin_lock_irq(&zone->lru_lock); |
| } else |
| list_add(&page->lru, &pages_to_free); |
| } |
| } |
| |
| /* |
| * To save our caller's stack, now use input list for pages to free. |
| */ |
| list_splice(&pages_to_free, page_list); |
| } |
| |
| /* |
| * 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 lruvec *lruvec, |
| struct scan_control *sc, enum lru_list lru) |
| { |
| LIST_HEAD(page_list); |
| unsigned long nr_scanned; |
| unsigned long nr_reclaimed = 0; |
| unsigned long nr_taken; |
| unsigned long nr_dirty = 0; |
| unsigned long nr_congested = 0; |
| unsigned long nr_unqueued_dirty = 0; |
| unsigned long nr_writeback = 0; |
| unsigned long nr_immediate = 0; |
| isolate_mode_t isolate_mode = 0; |
| int file = is_file_lru(lru); |
| struct zone *zone = lruvec_zone(lruvec); |
| struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; |
| |
| 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; |
| } |
| |
| lru_add_drain(); |
| |
| if (!sc->may_unmap) |
| isolate_mode |= ISOLATE_UNMAPPED; |
| if (!sc->may_writepage) |
| isolate_mode |= ISOLATE_CLEAN; |
| |
| spin_lock_irq(&zone->lru_lock); |
| |
| nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &page_list, |
| &nr_scanned, sc, isolate_mode, lru); |
| |
| __mod_zone_page_state(zone, NR_LRU_BASE + lru, -nr_taken); |
| __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, nr_taken); |
| |
| if (global_reclaim(sc)) { |
| 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); |
| } |
| spin_unlock_irq(&zone->lru_lock); |
| |
| if (nr_taken == 0) |
| return 0; |
| |
| nr_reclaimed = shrink_page_list(&page_list, zone, sc, TTU_UNMAP, |
| &nr_dirty, &nr_unqueued_dirty, &nr_congested, |
| &nr_writeback, &nr_immediate, |
| false); |
| |
| spin_lock_irq(&zone->lru_lock); |
| |
| reclaim_stat->recent_scanned[file] += nr_taken; |
| |
| if (global_reclaim(sc)) { |
| if (current_is_kswapd()) |
| __count_zone_vm_events(PGSTEAL_KSWAPD, zone, |
| nr_reclaimed); |
| else |
| __count_zone_vm_events(PGSTEAL_DIRECT, zone, |
| nr_reclaimed); |
| } |
| |
| putback_inactive_pages(lruvec, &page_list); |
| |
| __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken); |
| |
| spin_unlock_irq(&zone->lru_lock); |
| |
| free_hot_cold_page_list(&page_list, 1); |
| |
| /* |
| * If reclaim is isolating dirty pages under writeback, it implies |
| * that the long-lived page allocation rate is exceeding the page |
| * laundering rate. Either the global limits are not being effective |
| * at throttling processes due to the page distribution throughout |
| * zones or there is heavy usage of a slow backing device. The |
| * only option is to throttle from reclaim context which is not ideal |
| * as there is no guarantee the dirtying process is throttled in the |
| * same way balance_dirty_pages() manages. |
| * |
| * This scales the number of dirty pages that must be under writeback |
| * before a zone gets flagged ZONE_WRITEBACK. It is a simple backoff |
| * function that has the most effect in the range DEF_PRIORITY to |
| * DEF_PRIORITY-2 which is the priority reclaim is considered to be |
| * in trouble and reclaim is considered to be in trouble. |
| * |
| * DEF_PRIORITY 100% isolated pages must be PageWriteback to throttle |
| * DEF_PRIORITY-1 50% must be PageWriteback |
| * DEF_PRIORITY-2 25% must be PageWriteback, kswapd in trouble |
| * ... |
| * DEF_PRIORITY-6 For SWAP_CLUSTER_MAX isolated pages, throttle if any |
| * isolated page is PageWriteback |
| * |
| * Once a zone is flagged ZONE_WRITEBACK, kswapd will count the number |
| * of pages under pages flagged for immediate reclaim and stall if any |
| * are encountered in the nr_immediate check below. |
| */ |
| if (nr_writeback && nr_writeback >= |
| (nr_taken >> (DEF_PRIORITY - sc->priority))) |
| zone_set_flag(zone, ZONE_WRITEBACK); |
| |
| /* |
| * memcg will stall in page writeback so only consider forcibly |
| * stalling for global reclaim |
| */ |
| if (global_reclaim(sc)) { |
| /* |
| * Tag a zone as congested if all the dirty pages scanned were |
| * backed by a congested BDI and wait_iff_congested will stall. |
| */ |
| if (nr_dirty && nr_dirty == nr_congested) |
| zone_set_flag(zone, ZONE_CONGESTED); |
| |
| /* |
| * If dirty pages are scanned that are not queued for IO, it |
| * implies that flushers are not keeping up. In this case, flag |
| * the zone ZONE_TAIL_LRU_DIRTY and kswapd will start writing |
| * pages from reclaim context. It will forcibly stall in the |
| * next check. |
| */ |
| if (nr_unqueued_dirty == nr_taken) |
| zone_set_flag(zone, ZONE_TAIL_LRU_DIRTY); |
| |
| /* |
| * In addition, if kswapd scans pages marked marked for |
| * immediate reclaim and under writeback (nr_immediate), it |
| * implies that pages are cycling through the LRU faster than |
| * they are written so also forcibly stall. |
| */ |
| if (nr_unqueued_dirty == nr_taken || nr_immediate) |
| congestion_wait(BLK_RW_ASYNC, HZ/10); |
| } |
| |
| /* |
| * Stall direct reclaim for IO completions if underlying BDIs or zone |
| * is congested. Allow kswapd to continue until it starts encountering |
| * unqueued dirty pages or cycling through the LRU too quickly. |
| */ |
| if (!sc->hibernation_mode && !current_is_kswapd()) |
| wait_iff_congested(zone, BLK_RW_ASYNC, HZ/10); |
| |
| trace_mm_vmscan_lru_shrink_inactive(zone->zone_pgdat->node_id, |
| zone_idx(zone), |
| nr_scanned, nr_reclaimed, |
| sc->priority, |
| trace_shrink_flags(file)); |
| 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 lruvec *lruvec, |
| struct list_head *list, |
| struct list_head *pages_to_free, |
| enum lru_list lru) |
| { |
| struct zone *zone = lruvec_zone(lruvec); |
| unsigned long pgmoved = 0; |
| struct page *page; |
| int nr_pages; |
| |
| while (!list_empty(list)) { |
| page = lru_to_page(list); |
| lruvec = mem_cgroup_page_lruvec(page, zone); |
| |
| VM_BUG_ON(PageLRU(page)); |
| SetPageLRU(page); |
| |
| nr_pages = hpage_nr_pages(page); |
| mem_cgroup_update_lru_size(lruvec, lru, nr_pages); |
| list_move(&page->lru, &lruvec->lists[lru]); |
| pgmoved += nr_pages; |
| |
| if (put_page_testzero(page)) { |
| __ClearPageLRU(page); |
| __ClearPageActive(page); |
| del_page_from_lru_list(page, lruvec, lru); |
| |
| if (unlikely(PageCompound(page))) { |
| spin_unlock_irq(&zone->lru_lock); |
| (*get_compound_page_dtor(page))(page); |
| spin_lock_irq(&zone->lru_lock); |
| } else |
| list_add(&page->lru, pages_to_free); |
| } |
| } |
| __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_to_scan, |
| struct lruvec *lruvec, |
| struct scan_control *sc, |
| enum lru_list lru) |
| { |
| unsigned long nr_taken; |
| unsigned long nr_scanned; |
| 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 = &lruvec->reclaim_stat; |
| unsigned long nr_rotated = 0; |
| isolate_mode_t isolate_mode = 0; |
| int file = is_file_lru(lru); |
| struct zone *zone = lruvec_zone(lruvec); |
| |
| lru_add_drain(); |
| |
| if (!sc->may_unmap) |
| isolate_mode |= ISOLATE_UNMAPPED; |
| if (!sc->may_writepage) |
| isolate_mode |= ISOLATE_CLEAN; |
| |
| spin_lock_irq(&zone->lru_lock); |
| |
| nr_taken = isolate_lru_pages(nr_to_scan, lruvec, &l_hold, |
| &nr_scanned, sc, isolate_mode, lru); |
| if (global_reclaim(sc)) |
| zone->pages_scanned += nr_scanned; |
| |
| reclaim_stat->recent_scanned[file] += nr_taken; |
| |
| __count_zone_vm_events(PGREFILL, zone, nr_scanned); |
| __mod_zone_page_state(zone, NR_LRU_BASE + lru, -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))) { |
| putback_lru_page(page); |
| continue; |
| } |
| |
| if (unlikely(buffer_heads_over_limit)) { |
| if (page_has_private(page) && trylock_page(page)) { |
| if (page_has_private(page)) |
| try_to_release_page(page, 0); |
| unlock_page(page); |
| } |
| } |
| |
| if (page_referenced(page, 0, sc->target_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(lruvec, &l_active, &l_hold, lru); |
| move_active_pages_to_lru(lruvec, &l_inactive, &l_hold, lru - LRU_ACTIVE); |
| __mod_zone_page_state(zone, NR_ISOLATED_ANON + file, -nr_taken); |
| spin_unlock_irq(&zone->lru_lock); |
| |
| free_hot_cold_page_list(&l_hold, 1); |
| } |
| |
| #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 |
| * @lruvec: LRU vector to check |
| * |
| * 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 lruvec *lruvec) |
| { |
| /* |
| * If we don't have swap space, anonymous page deactivation |
| * is pointless. |
| */ |
| if (!total_swap_pages) |
| return 0; |
| |
| if (!mem_cgroup_disabled()) |
| return mem_cgroup_inactive_anon_is_low(lruvec); |
| |
| return inactive_anon_is_low_global(lruvec_zone(lruvec)); |
| } |
| #else |
| static inline int inactive_anon_is_low(struct lruvec *lruvec) |
| { |
| return 0; |
| } |
| #endif |
| |
| /** |
| * inactive_file_is_low - check if file pages need to be deactivated |
| * @lruvec: LRU vector to check |
| * |
| * 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 lruvec *lruvec) |
| { |
| unsigned long inactive; |
| unsigned long active; |
| |
| inactive = get_lru_size(lruvec, LRU_INACTIVE_FILE); |
| active = get_lru_size(lruvec, LRU_ACTIVE_FILE); |
| |
| return active > inactive; |
| } |
| |
| static int inactive_list_is_low(struct lruvec *lruvec, enum lru_list lru) |
| { |
| if (is_file_lru(lru)) |
| return inactive_file_is_low(lruvec); |
| else |
| return inactive_anon_is_low(lruvec); |
| } |
| |
| static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, |
| struct lruvec *lruvec, struct scan_control *sc) |
| { |
| if (is_active_lru(lru)) { |
| if (inactive_list_is_low(lruvec, lru)) |
| shrink_active_list(nr_to_scan, lruvec, sc, lru); |
| return 0; |
| } |
| |
| return shrink_inactive_list(nr_to_scan, lruvec, sc, lru); |
| } |
| |
| static int vmscan_swappiness(struct scan_control *sc) |
| { |
| if (global_reclaim(sc)) |
| return vm_swappiness; |
| return mem_cgroup_swappiness(sc->target_mem_cgroup); |
| } |
| |
| enum scan_balance { |
| SCAN_EQUAL, |
| SCAN_FRACT, |
| SCAN_ANON, |
| SCAN_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 inactive pages to scan; nr[1] = anon active pages to scan |
| * nr[2] = file inactive pages to scan; nr[3] = file active pages to scan |
| */ |
| static void get_scan_count(struct lruvec *lruvec, struct scan_control *sc, |
| unsigned long *nr) |
| { |
| struct zone_reclaim_stat *reclaim_stat = &lruvec->reclaim_stat; |
| u64 fraction[2]; |
| u64 denominator = 0; /* gcc */ |
| struct zone *zone = lruvec_zone(lruvec); |
| unsigned long anon_prio, file_prio; |
| enum scan_balance scan_balance; |
| unsigned long anon, file, free; |
| bool force_scan = false; |
| unsigned long ap, fp; |
| enum lru_list lru; |
| |
| /* |
| * If the zone or memcg is small, nr[l] can be 0. This |
| * results in no scanning on this priority and a potential |
| * priority drop. Global direct reclaim can go to the next |
| * zone and tends to have no problems. Global kswapd is for |
| * zone balancing and it needs to scan a minimum amount. When |
| * reclaiming for a memcg, a priority drop can cause high |
| * latencies, so it's better to scan a minimum amount there as |
| * well. |
| */ |
| if (current_is_kswapd() && zone->all_unreclaimable) |
| force_scan = true; |
| if (!global_reclaim(sc)) |
| force_scan = true; |
| |
| /* If we have no swap space, do not bother scanning anon pages. */ |
| if (!sc->may_swap || (get_nr_swap_pages() <= 0)) { |
| scan_balance = SCAN_FILE; |
| goto out; |
| } |
| |
| /* |
| * Global reclaim will swap to prevent OOM even with no |
| * swappiness, but memcg users want to use this knob to |
| * disable swapping for individual groups completely when |
| * using the memory controller's swap limit feature would be |
| * too expensive. |
| */ |
| if (!global_reclaim(sc) && !vmscan_swappiness(sc)) { |
| scan_balance = SCAN_FILE; |
| goto out; |
| } |
| |
| /* |
| * Do not apply any pressure balancing cleverness when the |
| * system is close to OOM, scan both anon and file equally |
| * (unless the swappiness setting disagrees with swapping). |
| */ |
| if (!sc->priority && vmscan_swappiness(sc)) { |
| scan_balance = SCAN_EQUAL; |
| goto out; |
| } |
| |
| anon = get_lru_size(lruvec, LRU_ACTIVE_ANON) + |
| get_lru_size(lruvec, LRU_INACTIVE_ANON); |
| file = get_lru_size(lruvec, LRU_ACTIVE_FILE) + |
| get_lru_size(lruvec, LRU_INACTIVE_FILE); |
| |
| /* |
| * If it's foreseeable that reclaiming the file cache won't be |
| * enough to get the zone back into a desirable shape, we have |
| * to swap. Better start now and leave the - probably heavily |
| * thrashing - remaining file pages alone. |
| */ |
| if (global_reclaim(sc)) { |
| free = zone_page_state(zone, NR_FREE_PAGES); |
| if (unlikely(file + free <= high_wmark_pages(zone))) { |
| scan_balance = SCAN_ANON; |
| goto out; |
| } |
| } |
| |
| /* |
| * There is enough inactive page cache, do not reclaim |
| * anything from the anonymous working set right now. |
| */ |
| if (!inactive_file_is_low(lruvec)) { |
| scan_balance = SCAN_FILE; |
| goto out; |
| } |
| |
| scan_balance = SCAN_FRACT; |
| |
| /* |
| * With swappiness at 100, anonymous and file have the same priority. |
| * This scanning priority is essentially the inverse of IO cost. |
| */ |
| anon_prio = vmscan_swappiness(sc); |
| file_prio = 200 - anon_prio; |
| |
| /* |
| * 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 * (reclaim_stat->recent_scanned[0] + 1); |
| ap /= reclaim_stat->recent_rotated[0] + 1; |
| |
| fp = file_prio * (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; |
| out: |
| for_each_evictable_lru(lru) { |
| int file = is_file_lru(lru); |
| unsigned long size; |
| unsigned long scan; |
| |
| size = get_lru_size(lruvec, lru); |
| scan = size >> sc->priority; |
| |
| if (!scan && force_scan) |
| scan = min(size, SWAP_CLUSTER_MAX); |
| |
| switch (scan_balance) { |
| case SCAN_EQUAL: |
| /* Scan lists relative to size */ |
| break; |
| case SCAN_FRACT: |
| /* |
| * Scan types proportional to swappiness and |
| * their relative recent reclaim efficiency. |
| */ |
| scan = div64_u64(scan * fraction[file], denominator); |
| break; |
| case SCAN_FILE: |
| case SCAN_ANON: |
| /* Scan one type exclusively */ |
| if ((scan_balance == SCAN_FILE) != file) |
| scan = 0; |
| break; |
| default: |
| /* Look ma, no brain */ |
| BUG(); |
| } |
| nr[lru] = scan; |
| } |
| } |
| |
| /* |
| * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. |
| */ |
| static void shrink_lruvec(struct lruvec *lruvec, struct scan_control *sc) |
| { |
| unsigned long nr[NR_LRU_LISTS]; |
| unsigned long targets[NR_LRU_LISTS]; |
| unsigned long nr_to_scan; |
| enum lru_list lru; |
| unsigned long nr_reclaimed = 0; |
| unsigned long nr_to_reclaim = sc->nr_to_reclaim; |
| struct blk_plug plug; |
| bool scan_adjusted = false; |
| |
| get_scan_count(lruvec, sc, nr); |
| |
| /* Record the original scan target for proportional adjustments later */ |
| memcpy(targets, nr, sizeof(nr)); |
| |
| blk_start_plug(&plug); |
| while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || |
| nr[LRU_INACTIVE_FILE]) { |
| unsigned long nr_anon, nr_file, percentage; |
| unsigned long nr_scanned; |
| |
| for_each_evictable_lru(lru) { |
| if (nr[lru]) { |
| nr_to_scan = min(nr[lru], SWAP_CLUSTER_MAX); |
| nr[lru] -= nr_to_scan; |
| |
| nr_reclaimed += shrink_list(lru, nr_to_scan, |
| lruvec, sc); |
| } |
| } |
| |
| if (nr_reclaimed < nr_to_reclaim || scan_adjusted) |
| continue; |
| |
| /* |
| * For global direct reclaim, reclaim only the number of pages |
| * requested. Less care is taken to scan proportionally as it |
| * is more important to minimise direct reclaim stall latency |
| * than it is to properly age the LRU lists. |
| */ |
| if (global_reclaim(sc) && !current_is_kswapd()) |
| break; |
| |
| /* |
| * For kswapd and memcg, reclaim at least the number of pages |
| * requested. Ensure that the anon and file LRUs shrink |
| * proportionally what was requested by get_scan_count(). We |
| * stop reclaiming one LRU and reduce the amount scanning |
| * proportional to the original scan target. |
| */ |
| nr_file = nr[LRU_INACTIVE_FILE] + nr[LRU_ACTIVE_FILE]; |
| nr_anon = nr[LRU_INACTIVE_ANON] + nr[LRU_ACTIVE_ANON]; |
| |
| if (nr_file > nr_anon) { |
| unsigned long scan_target = targets[LRU_INACTIVE_ANON] + |
| targets[LRU_ACTIVE_ANON] + 1; |
| lru = LRU_BASE; |
| percentage = nr_anon * 100 / scan_target; |
| } else { |
| unsigned long scan_target = targets[LRU_INACTIVE_FILE] + |
| targets[LRU_ACTIVE_FILE] + 1; |
| lru = LRU_FILE; |
| percentage = nr_file * 100 / scan_target; |
| } |
| |
| /* Stop scanning the smaller of the LRU */ |
| nr[lru] = 0; |
| nr[lru + LRU_ACTIVE] = 0; |
| |
| /* |
| * Recalculate the other LRU scan count based on its original |
| * scan target and the percentage scanning already complete |
| */ |
| lru = (lru == LRU_FILE) ? LRU_BASE : LRU_FILE; |
| nr_scanned = targets[lru] - nr[lru]; |
| nr[lru] = targets[lru] * (100 - percentage) / 100; |
| nr[lru] -= min(nr[lru], nr_scanned); |
| |
| lru += LRU_ACTIVE; |
| nr_scanned = targets[lru] - nr[lru]; |
| nr[lru] = targets[lru] * (100 - percentage) / 100; |
| nr[lru] -= min(nr[lru], nr_scanned); |
| |
| scan_adjusted = true; |
| } |
| blk_finish_plug(&plug); |
| 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(lruvec)) |
| shrink_active_list(SWAP_CLUSTER_MAX, lruvec, |
| sc, LRU_ACTIVE_ANON); |
| |
| throttle_vm_writeout(sc->gfp_mask); |
| } |
| |
| /* Use reclaim/compaction for costly allocs or under memory pressure */ |
| static bool in_reclaim_compaction(struct scan_control *sc) |
| { |
| if (IS_ENABLED(CONFIG_COMPACTION) && sc->order && |
| (sc->order > PAGE_ALLOC_COSTLY_ORDER || |
| sc->priority < DEF_PRIORITY - 2)) |
| return true; |
| |
| return false; |
| } |
| |
| /* |
| * Reclaim/compaction is used for high-order allocation requests. It reclaims |
| * order-0 pages before compacting the zone. should_continue_reclaim() returns |
| * true if more pages should be reclaimed such that when the page allocator |
| * calls try_to_compact_zone() that it will have enough free pages to succeed. |
| * It will give up earlier than that if there is difficulty reclaiming pages. |
| */ |
| 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 (!in_reclaim_compaction(sc)) |
| 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_page_state(zone, NR_INACTIVE_FILE); |
| if (get_nr_swap_pages() > 0) |
| inactive_lru_pages += zone_page_state(zone, NR_INACTIVE_ANON); |
| 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; |
| } |
| } |
| |
| static void shrink_zone(struct zone *zone, struct scan_control *sc) |
| { |
| unsigned long nr_reclaimed, nr_scanned; |
| |
| do { |
| struct mem_cgroup *root = sc->target_mem_cgroup; |
| struct mem_cgroup_reclaim_cookie reclaim = { |
| .zone = zone, |
| .priority = sc->priority, |
| }; |
| struct mem_cgroup *memcg; |
| |
| nr_reclaimed = sc->nr_reclaimed; |
| nr_scanned = sc->nr_scanned; |
| |
| memcg = mem_cgroup_iter(root, NULL, &reclaim); |
| do { |
| struct lruvec *lruvec; |
| |
| lruvec = mem_cgroup_zone_lruvec(zone, memcg); |
| |
| shrink_lruvec(lruvec, sc); |
| |
| /* |
| * Direct reclaim and kswapd have to scan all memory |
| * cgroups to fulfill the overall scan target for the |
| * zone. |
| * |
| * Limit reclaim, on the other hand, only cares about |
| * nr_to_reclaim pages to be reclaimed and it will |
| * retry with decreasing priority if one round over the |
| * whole hierarchy is not sufficient. |
| */ |
| if (!global_reclaim(sc) && |
| sc->nr_reclaimed >= sc->nr_to_reclaim) { |
| mem_cgroup_iter_break(root, memcg); |
| break; |
| } |
| memcg = mem_cgroup_iter(root, memcg, &reclaim); |
| } while (memcg); |
| |
| vmpressure(sc->gfp_mask, sc->target_mem_cgroup, |
| sc->nr_scanned - nr_scanned, |
| sc->nr_reclaimed - nr_reclaimed); |
| |
| } while (should_continue_reclaim(zone, sc->nr_reclaimed - nr_reclaimed, |
| sc->nr_scanned - nr_scanned, sc)); |
| } |
| |
| /* Returns true if compaction should go ahead for a high-order request */ |
| static inline bool compaction_ready(struct zone *zone, struct scan_control *sc) |
| { |
| unsigned long balance_gap, watermark; |
| bool watermark_ok; |
| |
| /* Do not consider compaction for orders reclaim is meant to satisfy */ |
| if (sc->order <= PAGE_ALLOC_COSTLY_ORDER) |
| return false; |
| |
| /* |
| * Compaction takes time to run and there are potentially other |
| * callers using the pages just freed. Continue reclaiming until |
| * there is a buffer of free pages available to give compaction |
| * a reasonable chance of completing and allocating the page |
| */ |
| balance_gap = min(low_wmark_pages(zone), |
| (zone->managed_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / |
| KSWAPD_ZONE_BALANCE_GAP_RATIO); |
| watermark = high_wmark_pages(zone) + balance_gap + (2UL << sc->order); |
| watermark_ok = zone_watermark_ok_safe(zone, 0, watermark, 0, 0); |
| |
| /* |
| * If compaction is deferred, reclaim up to a point where |
| * compaction will have a chance of success when re-enabled |
| */ |
| if (compaction_deferred(zone, sc->order)) |
| return watermark_ok; |
| |
| /* If compaction is not ready to start, keep reclaiming */ |
| if (!compaction_suitable(zone, sc->order)) |
| return false; |
| |
| return watermark_ok; |
| } |
| |
| /* |
| * 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. |
| * |
| * This function returns true if a zone is being reclaimed for a costly |
| * high-order allocation and compaction is ready to begin. This indicates to |
| * the caller that it should consider retrying the allocation instead of |
| * further reclaim. |
| */ |
| static bool shrink_zones(struct zonelist *zonelist, struct scan_control *sc) |
| { |
| struct zoneref *z; |
| struct zone *zone; |
| unsigned long nr_soft_reclaimed; |
| unsigned long nr_soft_scanned; |
| bool aborted_reclaim = false; |
| |
| /* |
| * If the number of buffer_heads in the machine exceeds the maximum |
| * allowed level, force direct reclaim to scan the highmem zone as |
| * highmem pages could be pinning lowmem pages storing buffer_heads |
| */ |
| if (buffer_heads_over_limit) |
| sc->gfp_mask |= __GFP_HIGHMEM; |
| |
| 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 (global_reclaim(sc)) { |
| if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
| continue; |
| if (zone->all_unreclaimable && |
| sc->priority != DEF_PRIORITY) |
| continue; /* Let kswapd poll it */ |
| if (IS_ENABLED(CONFIG_COMPACTION)) { |
| /* |
| * If we already have plenty of memory free for |
| * compaction in this zone, don't free any more. |
| * Even though compaction is invoked for any |
| * non-zero order, only frequent costly order |
| * reclamation is disruptive enough to become a |
| * noticeable problem, like transparent huge |
| * page allocations. |
| */ |
| if (compaction_ready(zone, sc)) { |
| aborted_reclaim = true; |
| continue; |
| } |
| } |
| /* |
| * 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(zone, sc); |
| } |
| |
| return aborted_reclaim; |
| } |
| |
| 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) |
| { |
| unsigned long total_scanned = 0; |
| struct reclaim_state *reclaim_state = current->reclaim_state; |
| struct zoneref *z; |
| struct zone *zone; |
| unsigned long writeback_threshold; |
| bool aborted_reclaim; |
| |
| delayacct_freepages_start(); |
| |
| if (global_reclaim(sc)) |
| count_vm_event(ALLOCSTALL); |
| |
| do { |
| vmpressure_prio(sc->gfp_mask, sc->target_mem_cgroup, |
| sc->priority); |
| sc->nr_scanned = 0; |
| aborted_reclaim = shrink_zones(zonelist, sc); |
| |
| /* |
| * Don't shrink slabs when reclaiming memory from |
| * over limit cgroups |
| */ |
| if (global_reclaim(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; |
| |
| /* |
| * If we're getting trouble reclaiming, start doing |
| * writepage even in laptop mode. |
| */ |
| if (sc->priority < DEF_PRIORITY - 2) |
| sc->may_writepage = 1; |
| |
| /* |
| * 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, |
| WB_REASON_TRY_TO_FREE_PAGES); |
| sc->may_writepage = 1; |
| } |
| } while (--sc->priority >= 0); |
| |
| out: |
| delayacct_freepages_end(); |
| |
| 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; |
| |
| /* Aborted reclaim to try compaction? don't OOM, then */ |
| if (aborted_reclaim) |
| return 1; |
| |
| /* top priority shrink_zones still had more to do? don't OOM, then */ |
| if (global_reclaim(sc) && !all_unreclaimable(zonelist, sc)) |
| return 1; |
| |
| return 0; |
| } |
| |
| static bool pfmemalloc_watermark_ok(pg_data_t *pgdat) |
| { |
| struct zone *zone; |
| unsigned long pfmemalloc_reserve = 0; |
| unsigned long free_pages = 0; |
| int i; |
| bool wmark_ok; |
| |
| for (i = 0; i <= ZONE_NORMAL; i++) { |
| zone = &pgdat->node_zones[i]; |
| pfmemalloc_reserve += min_wmark_pages(zone); |
| free_pages += zone_page_state(zone, NR_FREE_PAGES); |
| } |
| |
| wmark_ok = free_pages > pfmemalloc_reserve / 2; |
| |
| /* kswapd must be awake if processes are being throttled */ |
| if (!wmark_ok && waitqueue_active(&pgdat->kswapd_wait)) { |
| pgdat->classzone_idx = min(pgdat->classzone_idx, |
| (enum zone_type)ZONE_NORMAL); |
| wake_up_interruptible(&pgdat->kswapd_wait); |
| } |
| |
| return wmark_ok; |
| } |
| |
| /* |
| * Throttle direct reclaimers if backing storage is backed by the network |
| * and the PFMEMALLOC reserve for the preferred node is getting dangerously |
| * depleted. kswapd will continue to make progress and wake the processes |
| * when the low watermark is reached. |
| * |
| * Returns true if a fatal signal was delivered during throttling. If this |
| * happens, the page allocator should not consider triggering the OOM killer. |
| */ |
| static bool throttle_direct_reclaim(gfp_t gfp_mask, struct zonelist *zonelist, |
| nodemask_t *nodemask) |
| { |
| struct zone *zone; |
| int high_zoneidx = gfp_zone(gfp_mask); |
| pg_data_t *pgdat; |
| |
| /* |
| * Kernel threads should not be throttled as they may be indirectly |
| * responsible for cleaning pages necessary for reclaim to make forward |
| * progress. kjournald for example may enter direct reclaim while |
| * committing a transaction where throttling it could forcing other |
| * processes to block on log_wait_commit(). |
| */ |
| if (current->flags & PF_KTHREAD) |
| goto out; |
| |
| /* |
| * If a fatal signal is pending, this process should not throttle. |
| * It should return quickly so it can exit and free its memory |
| */ |
| if (fatal_signal_pending(current)) |
| goto out; |
| |
| /* Check if the pfmemalloc reserves are ok */ |
| first_zones_zonelist(zonelist, high_zoneidx, NULL, &zone); |
| pgdat = zone->zone_pgdat; |
| if (pfmemalloc_watermark_ok(pgdat)) |
| goto out; |
| |
| /* Account for the throttling */ |
| count_vm_event(PGSCAN_DIRECT_THROTTLE); |
| |
| /* |
| * If the caller cannot enter the filesystem, it's possible that it |
| * is due to the caller holding an FS lock or performing a journal |
| * transaction in the case of a filesystem like ext[3|4]. In this case, |
| * it is not safe to block on pfmemalloc_wait as kswapd could be |
| * blocked waiting on the same lock. Instead, throttle for up to a |
| * second before continuing. |
| */ |
| if (!(gfp_mask & __GFP_FS)) { |
| wait_event_interruptible_timeout(pgdat->pfmemalloc_wait, |
| pfmemalloc_watermark_ok(pgdat), HZ); |
| |
| goto check_pending; |
| } |
| |
| /* Throttle until kswapd wakes the process */ |
| wait_event_killable(zone->zone_pgdat->pfmemalloc_wait, |
| pfmemalloc_watermark_ok(pgdat)); |
| |
| check_pending: |
| if (fatal_signal_pending(current)) |
| return true; |
| |
| out: |
| return false; |
| } |
| |
| 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 = memalloc_noio_flags(gfp_mask)), |
| .may_writepage = !laptop_mode, |
| .nr_to_reclaim = SWAP_CLUSTER_MAX, |
| .may_unmap = 1, |
| .may_swap = 1, |
| .order = order, |
| .priority = DEF_PRIORITY, |
| .target_mem_cgroup = NULL, |
| .nodemask = nodemask, |
| }; |
| struct shrink_control shrink = { |
| .gfp_mask = sc.gfp_mask, |
| }; |
| |
| /* |
| * Do not enter reclaim if fatal signal was delivered while throttled. |
| * 1 is returned so that the page allocator does not OOM kill at this |
| * point. |
| */ |
| if (throttle_direct_reclaim(gfp_mask, zonelist, nodemask)) |
| return 1; |
| |
| 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_MEMCG |
| |
| unsigned long mem_cgroup_shrink_node_zone(struct mem_cgroup *memcg, |
| gfp_t gfp_mask, bool noswap, |
| 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, |
| .order = 0, |
| .priority = 0, |
| .target_mem_cgroup = memcg, |
| }; |
| struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg); |
| |
| sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | |
| (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); |
| |
| trace_mm_vmscan_memcg_softlimit_reclaim_begin(sc.order, |
| 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_lruvec(lruvec, &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 *memcg, |
| gfp_t gfp_mask, |
| bool noswap) |
| { |
| 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, |
| .order = 0, |
| .priority = DEF_PRIORITY, |
| .target_mem_cgroup = memcg, |
| .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(memcg); |
| |
| 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 |
| |
| static void age_active_anon(struct zone *zone, struct scan_control *sc) |
| { |
| struct mem_cgroup *memcg; |
| |
| if (!total_swap_pages) |
| return; |
| |
| memcg = mem_cgroup_iter(NULL, NULL, NULL); |
| do { |
| struct lruvec *lruvec = mem_cgroup_zone_lruvec(zone, memcg); |
| |
| if (inactive_anon_is_low(lruvec)) |
| shrink_active_list(SWAP_CLUSTER_MAX, lruvec, |
| sc, LRU_ACTIVE_ANON); |
| |
| memcg = mem_cgroup_iter(NULL, memcg, NULL); |
| } while (memcg); |
| } |
| |
| static bool zone_balanced(struct zone *zone, int order, |
| unsigned long balance_gap, int classzone_idx) |
| { |
| if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone) + |
| balance_gap, classzone_idx, 0)) |
| return false; |
| |
| if (IS_ENABLED(CONFIG_COMPACTION) && order && |
| !compaction_suitable(zone, order)) |
| return false; |
| |
| return true; |
| } |
| |
| /* |
| * pgdat_balanced() is used when checking if a node is balanced. |
| * |
| * For order-0, all zones must be 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, int order, int classzone_idx) |
| { |
| unsigned long managed_pages = 0; |
| unsigned long balanced_pages = 0; |
| int i; |
| |
| /* Check the watermark levels */ |
| for (i = 0; i <= classzone_idx; i++) { |
| struct zone *zone = pgdat->node_zones + i; |
| |
| if (!populated_zone(zone)) |
| continue; |
| |
| managed_pages += zone->managed_pages; |
| |
| /* |
| * A special case here: |
| * |
| * balance_pgdat() skips over all_unreclaimable after |
| * DEF_PRIORITY. Effectively, it considers them balanced so |
| * they must be considered balanced here as well! |
| */ |
| if (zone->all_unreclaimable) { |
| balanced_pages += zone->managed_pages; |
| continue; |
| } |
| |
| if (zone_balanced(zone, order, 0, i)) |
| balanced_pages += zone->managed_pages; |
| else if (!order) |
| return false; |
| } |
| |
| if (order) |
| return balanced_pages >= (managed_pages >> 2); |
| else |
| return true; |
| } |
| |
| /* |
| * Prepare kswapd for sleeping. This verifies that there are no processes |
| * waiting in throttle_direct_reclaim() and that watermarks have been met. |
| * |
| * Returns true if kswapd is ready to sleep |
| */ |
| static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining, |
| int classzone_idx) |
| { |
| /* If a direct reclaimer woke kswapd within HZ/10, it's premature */ |
| if (remaining) |
| return false; |
| |
| /* |
| * There is a potential race between when kswapd checks its watermarks |
| * and a process gets throttled. There is also a potential race if |
| * processes get throttled, kswapd wakes, a large process exits therby |
| * balancing the zones that causes kswapd to miss a wakeup. If kswapd |
| * is going to sleep, no process should be sleeping on pfmemalloc_wait |
| * so wake them now if necessary. If necessary, processes will wake |
| * kswapd and get throttled again |
| */ |
| if (waitqueue_active(&pgdat->pfmemalloc_wait)) { |
| wake_up(&pgdat->pfmemalloc_wait); |
| return false; |
| } |
| |
| return pgdat_balanced(pgdat, order, classzone_idx); |
| } |
| |
| /* |
| * kswapd shrinks the zone by the number of pages required to reach |
| * the high watermark. |
| * |
| * Returns true if kswapd scanned at least the requested number of pages to |
| * reclaim or if the lack of progress was due to pages under writeback. |
| * This is used to determine if the scanning priority needs to be raised. |
| */ |
| static bool kswapd_shrink_zone(struct zone *zone, |
| int classzone_idx, |
| struct scan_control *sc, |
| unsigned long lru_pages, |
| unsigned long *nr_attempted) |
| { |
| unsigned long nr_slab; |
| int testorder = sc->order; |
| unsigned long balance_gap; |
| struct reclaim_state *reclaim_state = current->reclaim_state; |
| struct shrink_control shrink = { |
| .gfp_mask = sc->gfp_mask, |
| }; |
| bool lowmem_pressure; |
| |
| /* Reclaim above the high watermark. */ |
| sc->nr_to_reclaim = max(SWAP_CLUSTER_MAX, high_wmark_pages(zone)); |
| |
| /* |
| * Kswapd reclaims only single pages with compaction enabled. Trying |
| * too hard to reclaim until contiguous free pages have become |
| * available can hurt performance by evicting too much useful data |
| * from memory. Do not reclaim more than needed for compaction. |
| */ |
| if (IS_ENABLED(CONFIG_COMPACTION) && sc->order && |
| compaction_suitable(zone, sc->order) != |
| COMPACT_SKIPPED) |
| testorder = 0; |
| |
| /* |
| * 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->managed_pages + KSWAPD_ZONE_BALANCE_GAP_RATIO-1) / |
| KSWAPD_ZONE_BALANCE_GAP_RATIO); |
| |
| /* |
| * If there is no low memory pressure or the zone is balanced then no |
| * reclaim is necessary |
| */ |
| lowmem_pressure = (buffer_heads_over_limit && is_highmem(zone)); |
| if (!lowmem_pressure && zone_balanced(zone, testorder, |
| balance_gap, classzone_idx)) |
| return true; |
| |
| shrink_zone(zone, sc); |
| |
| reclaim_state->reclaimed_slab = 0; |
| nr_slab = shrink_slab(&shrink, sc->nr_scanned, lru_pages); |
| sc->nr_reclaimed += reclaim_state->reclaimed_slab; |
| |
| /* Account for the number of pages attempted to reclaim */ |
| *nr_attempted += sc->nr_to_reclaim; |
| |
| if (nr_slab == 0 && !zone_reclaimable(zone)) |
| zone->all_unreclaimable = 1; |
| |
| zone_clear_flag(zone, ZONE_WRITEBACK); |
| |
| /* |
| * 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, speculatively avoid congestion |
| * waits. |
| */ |
| if (!zone->all_unreclaimable && |
| zone_balanced(zone, testorder, 0, classzone_idx)) { |
| zone_clear_flag(zone, ZONE_CONGESTED); |
| zone_clear_flag(zone, ZONE_TAIL_LRU_DIRTY); |
| } |
| |
| return sc->nr_scanned >= sc->nr_to_reclaim; |
| } |
| |
| /* |
| * 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 i; |
| int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ |
| unsigned long nr_soft_reclaimed; |
| unsigned long nr_soft_scanned; |
| struct scan_control sc = { |
| .gfp_mask = GFP_KERNEL, |
| .priority = DEF_PRIORITY, |
| .may_unmap = 1, |
| .may_swap = 1, |
| .may_writepage = !laptop_mode, |
| .order = order, |
| .target_mem_cgroup = NULL, |
| }; |
| count_vm_event(PAGEOUTRUN); |
| |
| do { |
| unsigned long lru_pages = 0; |
| unsigned long nr_attempted = 0; |
| bool raise_priority = true; |
| bool pgdat_needs_compaction = (order > 0); |
| |
| sc.nr_reclaimed = 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 && |
| sc.priority != DEF_PRIORITY) |
| continue; |
| |
| /* |
| * Do some background aging of the anon list, to give |
| * pages a chance to be referenced before reclaiming. |
| */ |
| age_active_anon(zone, &sc); |
| |
| /* |
| * If the number of buffer_heads in the machine |
| * exceeds the maximum allowed level and this node |
| * has a highmem zone, force kswapd to reclaim from |
| * it to relieve lowmem pressure. |
| */ |
| if (buffer_heads_over_limit && is_highmem_idx(i)) { |
| end_zone = i; |
| break; |
| } |
| |
| if (!zone_balanced(zone, order, 0, 0)) { |
| end_zone = i; |
| break; |
| } else { |
| /* |
| * If balanced, clear the dirty and congested |
| * flags |
| */ |
| zone_clear_flag(zone, ZONE_CONGESTED); |
| zone_clear_flag(zone, ZONE_TAIL_LRU_DIRTY); |
| } |
| } |
| |
| if (i < 0) |
| goto out; |
| |
| for (i = 0; i <= end_zone; i++) { |
| struct zone *zone = pgdat->node_zones + i; |
| |
| if (!populated_zone(zone)) |
| continue; |
| |
| lru_pages += zone_reclaimable_pages(zone); |
| |
| /* |
| * If any zone is currently balanced then kswapd will |
| * not call compaction as it is expected that the |
| * necessary pages are already available. |
| */ |
| if (pgdat_needs_compaction && |
| zone_watermark_ok(zone, order, |
| low_wmark_pages(zone), |
| *classzone_idx, 0)) |
| pgdat_needs_compaction = false; |
| } |
| |
| /* |
| * If we're getting trouble reclaiming, start doing writepage |
| * even in laptop mode. |
| */ |
| if (sc.priority < DEF_PRIORITY - 2) |
| sc.may_writepage = 1; |
| |
| /* |
| * 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; |
| |
| if (!populated_zone(zone)) |
| continue; |
| |
| if (zone->all_unreclaimable && |
| sc.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; |
| |
| /* |
| * There should be no need to raise the scanning |
| * priority if enough pages are already being scanned |
| * that that high watermark would be met at 100% |
| * efficiency. |
| */ |
| if (kswapd_shrink_zone(zone, end_zone, &sc, |
| lru_pages, &nr_attempted)) |
| raise_priority = false; |
| } |
| |
| /* |
| * If the low watermark is met there is no need for processes |
| * to be throttled on pfmemalloc_wait as they should not be |
| * able to safely make forward progress. Wake them |
| */ |
| if (waitqueue_active(&pgdat->pfmemalloc_wait) && |
| pfmemalloc_watermark_ok(pgdat)) |
| wake_up(&pgdat->pfmemalloc_wait); |
| |
| /* |
| * Fragmentation may mean that the system cannot be rebalanced |
| * for high-order allocations in all zones. If twice the |
| * allocation size has been reclaimed and the zones are still |
| * not balanced then recheck the watermarks at order-0 to |
| * prevent kswapd reclaiming excessively. Assume that a |
| * process requested a high-order can direct reclaim/compact. |
| */ |
| if (order && sc.nr_reclaimed >= 2UL << order) |
| order = sc.order = 0; |
| |
| /* Check if kswapd should be suspending */ |
| if (try_to_freeze() || kthread_should_stop()) |
| break; |
| |
| /* |
| * Compact if necessary and kswapd is reclaiming at least the |
| * high watermark number of pages as requsted |
| */ |
| if (pgdat_needs_compaction && sc.nr_reclaimed > nr_attempted) |
| compact_pgdat(pgdat, order); |
| |
| /* |
| * Raise priority if scanning rate is too low or there was no |
| * progress in reclaiming pages |
| */ |
| if (raise_priority || !sc.nr_reclaimed) |
| sc.priority--; |
| } while (sc.priority >= 1 && |
| !pgdat_balanced(pgdat, order, *classzone_idx)); |
| |
| out: |
| /* |
| * Return the order we were reclaiming at so prepare_kswapd_sleep() |
| * 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 (prepare_kswapd_sleep(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 (prepare_kswapd_sleep(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); |
| |
| /* |
| * Compaction records what page blocks it recently failed to |
| * isolate pages from and skips them in the future scanning. |
| * When kswapd is going to sleep, it is reasonable to assume |
| * that pages and compaction may succeed so reset the cache. |
| */ |
| reset_isolation_suitable(pgdat); |
| |
| if (!kthread_should_stop()) |
| 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; |
| unsigned balanced_order; |
| int classzone_idx, new_classzone_idx; |
| int balanced_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; |
| balanced_order = 0; |
| classzone_idx = new_classzone_idx = pgdat->nr_zones - 1; |
| balanced_classzone_idx = classzone_idx; |
| for ( ; ; ) { |
| bool 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 (balanced_classzone_idx >= new_classzone_idx && |
| balanced_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, balanced_order, |
| balanced_classzone_idx); |
| order = pgdat->kswapd_max_order; |
| classzone_idx = pgdat->classzone_idx; |
| new_order = order; |
| new_classzone_idx = 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); |
| balanced_classzone_idx = classzone_idx; |
| balanced_order = balance_pgdat(pgdat, order, |
| &balanced_classzone_idx); |
| } |
| } |
| |
| current->reclaim_state = NULL; |
| 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 (get_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 (get_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, |
| .order = 0, |
| .priority = DEF_PRIORITY, |
| }; |
| 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 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_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); |
| pr_err("Failed to start kswapd on node %d\n", nid); |
| ret = PTR_ERR(pgdat->kswapd); |
| pgdat->kswapd = NULL; |
| } |
| return ret; |
| } |
| |
| /* |
| * Called by memory hotplug when all memory in a node is offlined. Caller must |
| * hold lock_memory_hotplug(). |
| */ |
| void kswapd_stop(int nid) |
| { |
| struct task_struct *kswapd = NODE_DATA(nid)->kswapd; |
| |
| if (kswapd) { |
| kthread_stop(kswapd); |
| NODE_DATA(nid)->kswapd = NULL; |
| } |
| } |
| |
| static int __init kswapd_init(void) |
| { |
| int nid; |
| |
| swap_setup(); |
| for_each_node_state(nid, N_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; |
| 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(nr_pages, SWAP_CLUSTER_MAX), |
| .gfp_mask = (gfp_mask = memalloc_noio_flags(gfp_mask)), |
| .order = order, |
| .priority = ZONE_RECLAIM_PRIORITY, |
| }; |
| 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. |
| */ |
| do { |
| shrink_zone(zone, &sc); |
| } while (sc.nr_reclaimed < nr_pages && --sc.priority >= 0); |
| } |
| |
| 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 |
| * |
| * Test whether page is evictable--i.e., should be placed on active/inactive |
| * lists vs unevictable list. |
| * |
| * 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) |
| { |
| return !mapping_unevictable(page_mapping(page)) && !PageMlocked(page); |
| } |
| |
| #ifdef CONFIG_SHMEM |
| /** |
| * check_move_unevictable_pages - check pages for evictability and move to appropriate zone lru list |
| * @pages: array of pages to check |
| * @nr_pages: number of pages to check |
| * |
| * Checks pages for evictability and moves them to the appropriate lru list. |
| * |
| * This function is only used for SysV IPC SHM_UNLOCK. |
| */ |
| void check_move_unevictable_pages(struct page **pages, int nr_pages) |
| { |
| struct lruvec *lruvec; |
| struct zone *zone = NULL; |
| int pgscanned = 0; |
| int pgrescued = 0; |
| int i; |
| |
| for (i = 0; i < nr_pages; i++) { |
| struct page *page = pages[i]; |
| struct zone *pagezone; |
| |
| pgscanned++; |
| pagezone = page_zone(page); |
| if (pagezone != zone) { |
| if (zone) |
| spin_unlock_irq(&zone->lru_lock); |
| zone = pagezone; |
| spin_lock_irq(&zone->lru_lock); |
| } |
| lruvec = mem_cgroup_page_lruvec(page, zone); |
| |
| if (!PageLRU(page) || !PageUnevictable(page)) |
| continue; |
| |
| if (page_evictable(page)) { |
| enum lru_list lru = page_lru_base_type(page); |
| |
| VM_BUG_ON(PageActive(page)); |
| ClearPageUnevictable(page); |
| del_page_from_lru_list(page, lruvec, LRU_UNEVICTABLE); |
| add_page_to_lru_list(page, lruvec, lru); |
| pgrescued++; |
| } |
| } |
| |
| if (zone) { |
| __count_vm_events(UNEVICTABLE_PGRESCUED, pgrescued); |
| __count_vm_events(UNEVICTABLE_PGSCANNED, pgscanned); |
| spin_unlock_irq(&zone->lru_lock); |
| } |
| } |
| #endif /* CONFIG_SHMEM */ |
| |
| static void warn_scan_unevictable_pages(void) |
| { |
| printk_once(KERN_WARNING |
| "%s: The scan_unevictable_pages sysctl/node-interface has been " |
| "disabled for lack of a legitimate use case. If you have " |
| "one, please send an email to linux-mm@kvack.org.\n", |
| current->comm); |
| } |
| |
| /* |
| * 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) |
| { |
| warn_scan_unevictable_pages(); |
| proc_doulongvec_minmax(table, write, buffer, length, ppos); |
| 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 device *dev, |
| struct device_attribute *attr, |
| char *buf) |
| { |
| warn_scan_unevictable_pages(); |
| return sprintf(buf, "0\n"); /* always zero; should fit... */ |
| } |
| |
| static ssize_t write_scan_unevictable_node(struct device *dev, |
| struct device_attribute *attr, |
| const char *buf, size_t count) |
| { |
| warn_scan_unevictable_pages(); |
| return 1; |
| } |
| |
| |
| static DEVICE_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 device_create_file(&node->dev, &dev_attr_scan_unevictable_pages); |
| } |
| |
| void scan_unevictable_unregister_node(struct node *node) |
| { |
| device_remove_file(&node->dev, &dev_attr_scan_unevictable_pages); |
| } |
| #endif |