| /* |
| * 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/slab.h> |
| #include <linux/kernel_stat.h> |
| #include <linux/swap.h> |
| #include <linux/pagemap.h> |
| #include <linux/init.h> |
| #include <linux/highmem.h> |
| #include <linux/vmstat.h> |
| #include <linux/file.h> |
| #include <linux/writeback.h> |
| #include <linux/blkdev.h> |
| #include <linux/buffer_head.h> /* for try_to_release_page(), |
| buffer_heads_over_limit */ |
| #include <linux/mm_inline.h> |
| #include <linux/pagevec.h> |
| #include <linux/backing-dev.h> |
| #include <linux/rmap.h> |
| #include <linux/topology.h> |
| #include <linux/cpu.h> |
| #include <linux/cpuset.h> |
| #include <linux/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 <asm/tlbflush.h> |
| #include <asm/div64.h> |
| |
| #include <linux/swapops.h> |
| |
| #include "internal.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; |
| |
| /* 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; |
| |
| /* This context's SWAP_CLUSTER_MAX. If freeing memory for |
| * suspend, we effectively ignore SWAP_CLUSTER_MAX. |
| * In this context, it doesn't matter that we scan the |
| * whole list at once. */ |
| int swap_cluster_max; |
| |
| int swappiness; |
| |
| int all_unreclaimable; |
| |
| int order; |
| |
| /* Which cgroup do we reclaim from */ |
| struct mem_cgroup *mem_cgroup; |
| |
| /* |
| * Nodemask of nodes allowed by the caller. If NULL, all nodes |
| * are scanned. |
| */ |
| nodemask_t *nodemask; |
| |
| /* Pluggable isolate pages callback */ |
| unsigned long (*isolate_pages)(unsigned long nr, struct list_head *dst, |
| unsigned long *scanned, int order, int mode, |
| struct zone *z, struct mem_cgroup *mem_cont, |
| int active, int file); |
| }; |
| |
| #define lru_to_page(_head) (list_entry((_head)->prev, struct page, lru)) |
| |
| #ifdef ARCH_HAS_PREFETCH |
| #define prefetch_prev_lru_page(_page, _base, _field) \ |
| do { \ |
| if ((_page)->lru.prev != _base) { \ |
| struct page *prev; \ |
| \ |
| prev = lru_to_page(&(_page->lru)); \ |
| prefetch(&prev->_field); \ |
| } \ |
| } while (0) |
| #else |
| #define prefetch_prev_lru_page(_page, _base, _field) do { } while (0) |
| #endif |
| |
| #ifdef ARCH_HAS_PREFETCHW |
| #define prefetchw_prev_lru_page(_page, _base, _field) \ |
| do { \ |
| if ((_page)->lru.prev != _base) { \ |
| struct page *prev; \ |
| \ |
| prev = lru_to_page(&(_page->lru)); \ |
| prefetchw(&prev->_field); \ |
| } \ |
| } while (0) |
| #else |
| #define prefetchw_prev_lru_page(_page, _base, _field) do { } while (0) |
| #endif |
| |
| /* |
| * From 0 .. 100. Higher means more swappy. |
| */ |
| int vm_swappiness = 60; |
| long vm_total_pages; /* The total number of pages which the VM controls */ |
| |
| static LIST_HEAD(shrinker_list); |
| static DECLARE_RWSEM(shrinker_rwsem); |
| |
| #ifdef CONFIG_CGROUP_MEM_RES_CTLR |
| #define scanning_global_lru(sc) (!(sc)->mem_cgroup) |
| #else |
| #define scanning_global_lru(sc) (1) |
| #endif |
| |
| static struct zone_reclaim_stat *get_reclaim_stat(struct zone *zone, |
| struct scan_control *sc) |
| { |
| if (!scanning_global_lru(sc)) |
| return mem_cgroup_get_reclaim_stat(sc->mem_cgroup, zone); |
| |
| return &zone->reclaim_stat; |
| } |
| |
| static unsigned long zone_nr_pages(struct zone *zone, struct scan_control *sc, |
| enum lru_list lru) |
| { |
| if (!scanning_global_lru(sc)) |
| return mem_cgroup_zone_nr_pages(sc->mem_cgroup, zone, lru); |
| |
| return zone_page_state(zone, NR_LRU_BASE + lru); |
| } |
| |
| |
| /* |
| * Add a shrinker callback to be called from the vm |
| */ |
| void register_shrinker(struct shrinker *shrinker) |
| { |
| shrinker->nr = 0; |
| down_write(&shrinker_rwsem); |
| list_add_tail(&shrinker->list, &shrinker_list); |
| up_write(&shrinker_rwsem); |
| } |
| EXPORT_SYMBOL(register_shrinker); |
| |
| /* |
| * Remove one |
| */ |
| void unregister_shrinker(struct shrinker *shrinker) |
| { |
| down_write(&shrinker_rwsem); |
| list_del(&shrinker->list); |
| up_write(&shrinker_rwsem); |
| } |
| EXPORT_SYMBOL(unregister_shrinker); |
| |
| #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(unsigned long scanned, gfp_t gfp_mask, |
| unsigned long lru_pages) |
| { |
| struct shrinker *shrinker; |
| unsigned long ret = 0; |
| |
| if (scanned == 0) |
| scanned = SWAP_CLUSTER_MAX; |
| |
| if (!down_read_trylock(&shrinker_rwsem)) |
| return 1; /* Assume we'll be able to shrink next time */ |
| |
| list_for_each_entry(shrinker, &shrinker_list, list) { |
| unsigned long long delta; |
| unsigned long total_scan; |
| unsigned long max_pass = (*shrinker->shrink)(0, gfp_mask); |
| |
| delta = (4 * scanned) / shrinker->seeks; |
| delta *= max_pass; |
| do_div(delta, lru_pages + 1); |
| shrinker->nr += delta; |
| if (shrinker->nr < 0) { |
| printk(KERN_ERR "shrink_slab: %pF negative objects to " |
| "delete nr=%ld\n", |
| shrinker->shrink, shrinker->nr); |
| shrinker->nr = max_pass; |
| } |
| |
| /* |
| * Avoid risking looping forever due to too large nr value: |
| * never try to free more than twice the estimate number of |
| * freeable entries. |
| */ |
| if (shrinker->nr > max_pass * 2) |
| shrinker->nr = max_pass * 2; |
| |
| total_scan = shrinker->nr; |
| shrinker->nr = 0; |
| |
| while (total_scan >= SHRINK_BATCH) { |
| long this_scan = SHRINK_BATCH; |
| int shrink_ret; |
| int nr_before; |
| |
| nr_before = (*shrinker->shrink)(0, gfp_mask); |
| shrink_ret = (*shrinker->shrink)(this_scan, gfp_mask); |
| if (shrink_ret == -1) |
| break; |
| if (shrink_ret < nr_before) |
| ret += nr_before - shrink_ret; |
| count_vm_events(SLABS_SCANNED, this_scan); |
| total_scan -= this_scan; |
| |
| cond_resched(); |
| } |
| |
| shrinker->nr += total_scan; |
| } |
| up_read(&shrinker_rwsem); |
| return ret; |
| } |
| |
| /* Called without lock on whether page is mapped, so answer is unstable */ |
| static inline int page_mapping_inuse(struct page *page) |
| { |
| struct address_space *mapping; |
| |
| /* Page is in somebody's page tables. */ |
| if (page_mapped(page)) |
| return 1; |
| |
| /* Be more reluctant to reclaim swapcache than pagecache */ |
| if (PageSwapCache(page)) |
| return 1; |
| |
| mapping = page_mapping(page); |
| if (!mapping) |
| return 0; |
| |
| /* File is mmap'd by somebody? */ |
| return mapping_mapped(mapping); |
| } |
| |
| static inline int is_page_cache_freeable(struct page *page) |
| { |
| return page_count(page) - !!page_has_private(page) == 2; |
| } |
| |
| static int may_write_to_queue(struct backing_dev_info *bdi) |
| { |
| 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); |
| } |
| |
| /* Request for sync pageout. */ |
| enum pageout_io { |
| PAGEOUT_IO_ASYNC, |
| PAGEOUT_IO_SYNC, |
| }; |
| |
| /* 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, |
| enum pageout_io sync_writeback) |
| { |
| /* |
| * 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_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. |
| * See swapfile.c:page_queue_congested(). |
| */ |
| 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)) |
| 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, |
| .nonblocking = 1, |
| .for_reclaim = 1, |
| }; |
| |
| SetPageReclaim(page); |
| res = mapping->a_ops->writepage(page, &wbc); |
| if (res < 0) |
| handle_write_error(mapping, page, res); |
| if (res == AOP_WRITEPAGE_ACTIVATE) { |
| ClearPageReclaim(page); |
| return PAGE_ACTIVATE; |
| } |
| |
| /* |
| * Wait on writeback if requested to. This happens when |
| * direct reclaiming a large contiguous area and the |
| * first attempt to free a range of pages fails. |
| */ |
| if (PageWriteback(page) && sync_writeback == PAGEOUT_IO_SYNC) |
| wait_on_page_writeback(page); |
| |
| if (!PageWriteback(page)) { |
| /* synchronous write or broken a_ops? */ |
| ClearPageReclaim(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); |
| mem_cgroup_uncharge_swapcache(page, swap); |
| swap_free(swap); |
| } else { |
| __remove_from_page_cache(page); |
| spin_unlock_irq(&mapping->tree_lock); |
| mem_cgroup_uncharge_cache_page(page); |
| } |
| |
| return 1; |
| |
| cannot_free: |
| spin_unlock_irq(&mapping->tree_lock); |
| return 0; |
| } |
| |
| /* |
| * Attempt to detach a locked page from its ->mapping. If it is dirty or if |
| * someone else has a ref on the page, abort and return 0. If it was |
| * successfully detached, return 1. Assumes the caller has a single ref on |
| * this page. |
| */ |
| int remove_mapping(struct address_space *mapping, struct page *page) |
| { |
| if (__remove_mapping(mapping, page)) { |
| /* |
| * Unfreezing the refcount with 1 rather than 2 effectively |
| * drops the pagecache ref for us without requiring another |
| * atomic operation. |
| */ |
| page_unfreeze_refs(page, 1); |
| return 1; |
| } |
| return 0; |
| } |
| |
| /** |
| * putback_lru_page - put previously isolated page onto appropriate LRU list |
| * @page: page to be put back to appropriate lru list |
| * |
| * Add previously isolated @page to appropriate LRU list. |
| * Page may still be unevictable for other reasons. |
| * |
| * lru_lock must not be held, interrupts must be enabled. |
| */ |
| void putback_lru_page(struct page *page) |
| { |
| int lru; |
| int active = !!TestClearPageActive(page); |
| int was_unevictable = PageUnevictable(page); |
| |
| VM_BUG_ON(PageLRU(page)); |
| |
| redo: |
| ClearPageUnevictable(page); |
| |
| if (page_evictable(page, NULL)) { |
| /* |
| * For evictable pages, we can use the cache. |
| * In event of a race, worst case is we end up with an |
| * unevictable page on [in]active list. |
| * We know how to handle that. |
| */ |
| lru = active + page_is_file_cache(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); |
| } |
| |
| /* |
| * page's status can change while we move it among lru. If an evictable |
| * page is on unevictable list, it never be freed. To avoid that, |
| * check after we added it to the list, again. |
| */ |
| if (lru == LRU_UNEVICTABLE && page_evictable(page, NULL)) { |
| if (!isolate_lru_page(page)) { |
| put_page(page); |
| goto redo; |
| } |
| /* This means someone else dropped this page from LRU |
| * So, it will be freed or putback to LRU again. There is |
| * nothing to do here. |
| */ |
| } |
| |
| if (was_unevictable && lru != LRU_UNEVICTABLE) |
| count_vm_event(UNEVICTABLE_PGRESCUED); |
| else if (!was_unevictable && lru == LRU_UNEVICTABLE) |
| count_vm_event(UNEVICTABLE_PGCULLED); |
| |
| put_page(page); /* drop ref from isolate */ |
| } |
| |
| /* |
| * shrink_page_list() returns the number of reclaimed pages |
| */ |
| static unsigned long shrink_page_list(struct list_head *page_list, |
| struct scan_control *sc, |
| enum pageout_io sync_writeback) |
| { |
| LIST_HEAD(ret_pages); |
| struct pagevec freed_pvec; |
| int pgactivate = 0; |
| unsigned long nr_reclaimed = 0; |
| |
| cond_resched(); |
| |
| pagevec_init(&freed_pvec, 1); |
| while (!list_empty(page_list)) { |
| struct address_space *mapping; |
| struct page *page; |
| int may_enter_fs; |
| int referenced; |
| |
| cond_resched(); |
| |
| page = lru_to_page(page_list); |
| list_del(&page->lru); |
| |
| if (!trylock_page(page)) |
| goto keep; |
| |
| VM_BUG_ON(PageActive(page)); |
| |
| sc->nr_scanned++; |
| |
| if (unlikely(!page_evictable(page, NULL))) |
| goto cull_mlocked; |
| |
| if (!sc->may_unmap && page_mapped(page)) |
| goto keep_locked; |
| |
| /* Double the slab pressure for mapped and swapcache pages */ |
| if (page_mapped(page) || PageSwapCache(page)) |
| sc->nr_scanned++; |
| |
| may_enter_fs = (sc->gfp_mask & __GFP_FS) || |
| (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); |
| |
| if (PageWriteback(page)) { |
| /* |
| * Synchronous reclaim is performed in two passes, |
| * first an asynchronous pass over the list to |
| * start parallel writeback, and a second synchronous |
| * pass to wait for the IO to complete. Wait here |
| * for any page for which writeback has already |
| * started. |
| */ |
| if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs) |
| wait_on_page_writeback(page); |
| else |
| goto keep_locked; |
| } |
| |
| referenced = page_referenced(page, 1, sc->mem_cgroup); |
| /* In active use or really unfreeable? Activate it. */ |
| if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && |
| referenced && page_mapping_inuse(page)) |
| goto activate_locked; |
| |
| /* |
| * Anonymous process memory has backing store? |
| * Try to allocate it some swap space here. |
| */ |
| if (PageAnon(page) && !PageSwapCache(page)) { |
| if (!(sc->gfp_mask & __GFP_IO)) |
| goto keep_locked; |
| if (!add_to_swap(page)) |
| goto activate_locked; |
| may_enter_fs = 1; |
| } |
| |
| mapping = page_mapping(page); |
| |
| /* |
| * The page is mapped into the page tables of one or more |
| * processes. Try to unmap it here. |
| */ |
| if (page_mapped(page) && mapping) { |
| switch (try_to_unmap(page, 0)) { |
| 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)) { |
| if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced) |
| 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, sync_writeback)) { |
| case PAGE_KEEP: |
| goto keep_locked; |
| case PAGE_ACTIVATE: |
| goto activate_locked; |
| case PAGE_SUCCESS: |
| if (PageWriteback(page) || 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++; |
| if (!pagevec_add(&freed_pvec, page)) { |
| __pagevec_free(&freed_pvec); |
| pagevec_reinit(&freed_pvec); |
| } |
| 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)); |
| } |
| list_splice(&ret_pages, page_list); |
| if (pagevec_count(&freed_pvec)) |
| __pagevec_free(&freed_pvec); |
| count_vm_events(PGACTIVATE, pgactivate); |
| return nr_reclaimed; |
| } |
| |
| /* LRU Isolation modes. */ |
| #define ISOLATE_INACTIVE 0 /* Isolate inactive pages. */ |
| #define ISOLATE_ACTIVE 1 /* Isolate active pages. */ |
| #define ISOLATE_BOTH 2 /* Isolate both active and inactive pages. */ |
| |
| /* |
| * Attempt to remove the specified page from its LRU. Only take this page |
| * if it is of the appropriate PageActive status. Pages which are being |
| * freed elsewhere are also ignored. |
| * |
| * page: page to consider |
| * mode: one of the LRU isolation modes defined above |
| * |
| * returns 0 on success, -ve errno on failure. |
| */ |
| int __isolate_lru_page(struct page *page, int mode, int file) |
| { |
| int ret = -EINVAL; |
| |
| /* Only take pages on the LRU. */ |
| if (!PageLRU(page)) |
| return ret; |
| |
| /* |
| * When checking the active state, we need to be sure we are |
| * dealing with comparible boolean values. Take the logical not |
| * of each. |
| */ |
| if (mode != ISOLATE_BOTH && (!PageActive(page) != !mode)) |
| return ret; |
| |
| if (mode != ISOLATE_BOTH && (!page_is_file_cache(page) != !file)) |
| return ret; |
| |
| /* |
| * When this function is being called for lumpy reclaim, we |
| * initially look into all LRU pages, active, inactive and |
| * unevictable; only give shrink_page_list evictable pages. |
| */ |
| if (PageUnevictable(page)) |
| return ret; |
| |
| ret = -EBUSY; |
| |
| if (likely(get_page_unless_zero(page))) { |
| /* |
| * Be careful not to clear PageLRU until after we're |
| * sure the page is not being freed elsewhere -- the |
| * page release code relies on it. |
| */ |
| ClearPageLRU(page); |
| ret = 0; |
| mem_cgroup_del_lru(page); |
| } |
| |
| return ret; |
| } |
| |
| /* |
| * zone->lru_lock is heavily contended. Some of the functions that |
| * shrink the lists perform better by taking out a batch of pages |
| * and working on them outside the LRU lock. |
| * |
| * For pagecache intensive workloads, this function is the hottest |
| * spot in the kernel (apart from copy_*_user functions). |
| * |
| * Appropriate locks must be held before calling this function. |
| * |
| * @nr_to_scan: The number of pages to look through on the list. |
| * @src: The LRU list to pull pages off. |
| * @dst: The temp list to put pages on to. |
| * @scanned: The number of pages that were scanned. |
| * @order: The caller's attempted allocation order |
| * @mode: One of the LRU isolation modes |
| * @file: True [1] if isolating file [!anon] pages |
| * |
| * returns how many pages were moved onto *@dst. |
| */ |
| static unsigned long isolate_lru_pages(unsigned long nr_to_scan, |
| struct list_head *src, struct list_head *dst, |
| unsigned long *scanned, int order, int mode, int file) |
| { |
| unsigned long nr_taken = 0; |
| unsigned long scan; |
| |
| for (scan = 0; scan < nr_to_scan && !list_empty(src); scan++) { |
| struct page *page; |
| unsigned long pfn; |
| unsigned long end_pfn; |
| unsigned long page_pfn; |
| int zone_id; |
| |
| page = lru_to_page(src); |
| prefetchw_prev_lru_page(page, src, flags); |
| |
| VM_BUG_ON(!PageLRU(page)); |
| |
| switch (__isolate_lru_page(page, mode, file)) { |
| case 0: |
| list_move(&page->lru, dst); |
| nr_taken++; |
| break; |
| |
| case -EBUSY: |
| /* else it is being freed elsewhere */ |
| list_move(&page->lru, src); |
| continue; |
| |
| default: |
| BUG(); |
| } |
| |
| if (!order) |
| continue; |
| |
| /* |
| * Attempt to take all pages in the order aligned region |
| * surrounding the tag page. Only take those pages of |
| * the same active state as that tag page. We may safely |
| * round the target page pfn down to the requested order |
| * as the mem_map is guarenteed valid out to MAX_ORDER, |
| * where that page is in a different zone we will detect |
| * it from its zone id and abort this block scan. |
| */ |
| zone_id = page_zone_id(page); |
| page_pfn = page_to_pfn(page); |
| pfn = page_pfn & ~((1 << order) - 1); |
| end_pfn = pfn + (1 << order); |
| for (; pfn < end_pfn; pfn++) { |
| struct page *cursor_page; |
| |
| /* The target page is in the block, ignore it. */ |
| if (unlikely(pfn == page_pfn)) |
| continue; |
| |
| /* Avoid holes within the zone. */ |
| if (unlikely(!pfn_valid_within(pfn))) |
| break; |
| |
| cursor_page = pfn_to_page(pfn); |
| |
| /* Check that we have not crossed a zone boundary. */ |
| if (unlikely(page_zone_id(cursor_page) != zone_id)) |
| continue; |
| switch (__isolate_lru_page(cursor_page, mode, file)) { |
| case 0: |
| list_move(&cursor_page->lru, dst); |
| nr_taken++; |
| scan++; |
| break; |
| |
| case -EBUSY: |
| /* else it is being freed elsewhere */ |
| list_move(&cursor_page->lru, src); |
| default: |
| break; /* ! on LRU or wrong list */ |
| } |
| } |
| } |
| |
| *scanned = scan; |
| return nr_taken; |
| } |
| |
| static unsigned long isolate_pages_global(unsigned long nr, |
| struct list_head *dst, |
| unsigned long *scanned, int order, |
| int mode, struct zone *z, |
| struct mem_cgroup *mem_cont, |
| int active, int file) |
| { |
| int lru = LRU_BASE; |
| if (active) |
| lru += LRU_ACTIVE; |
| if (file) |
| lru += LRU_FILE; |
| return isolate_lru_pages(nr, &z->lru[lru].list, dst, scanned, order, |
| mode, !!file); |
| } |
| |
| /* |
| * clear_active_flags() is a helper for shrink_active_list(), clearing |
| * any active bits from the pages in the list. |
| */ |
| static unsigned long clear_active_flags(struct list_head *page_list, |
| unsigned int *count) |
| { |
| int nr_active = 0; |
| int lru; |
| struct page *page; |
| |
| list_for_each_entry(page, page_list, lru) { |
| lru = page_is_file_cache(page); |
| if (PageActive(page)) { |
| lru += LRU_ACTIVE; |
| ClearPageActive(page); |
| nr_active++; |
| } |
| count[lru]++; |
| } |
| |
| return nr_active; |
| } |
| |
| /** |
| * isolate_lru_page - tries to isolate a page from its LRU list |
| * @page: page to isolate from its LRU list |
| * |
| * Isolates a @page from an LRU list, clears PageLRU and adjusts the |
| * vmstat statistic corresponding to whatever LRU list the page was on. |
| * |
| * Returns 0 if the page was removed from an LRU list. |
| * Returns -EBUSY if the page was not on an LRU list. |
| * |
| * The returned page will have PageLRU() cleared. If it was found on |
| * the active list, it will have PageActive set. If it was found on |
| * the unevictable list, it will have the PageUnevictable bit set. That flag |
| * may need to be cleared by the caller before letting the page go. |
| * |
| * The vmstat statistic corresponding to the list on which the page was |
| * found will be decremented. |
| * |
| * Restrictions: |
| * (1) Must be called with an elevated refcount on the page. This is a |
| * fundamentnal difference from isolate_lru_pages (which is called |
| * without a stable reference). |
| * (2) the lru_lock must not be held. |
| * (3) interrupts must be enabled. |
| */ |
| int isolate_lru_page(struct page *page) |
| { |
| int ret = -EBUSY; |
| |
| if (PageLRU(page)) { |
| struct zone *zone = page_zone(page); |
| |
| spin_lock_irq(&zone->lru_lock); |
| if (PageLRU(page) && get_page_unless_zero(page)) { |
| int lru = page_lru(page); |
| ret = 0; |
| ClearPageLRU(page); |
| |
| del_page_from_lru_list(zone, page, lru); |
| } |
| spin_unlock_irq(&zone->lru_lock); |
| } |
| return ret; |
| } |
| |
| /* |
| * shrink_inactive_list() is a helper for shrink_zone(). It returns the number |
| * of reclaimed pages |
| */ |
| static unsigned long shrink_inactive_list(unsigned long max_scan, |
| struct zone *zone, struct scan_control *sc, |
| int priority, int file) |
| { |
| LIST_HEAD(page_list); |
| struct pagevec pvec; |
| unsigned long nr_scanned = 0; |
| unsigned long nr_reclaimed = 0; |
| struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); |
| int lumpy_reclaim = 0; |
| |
| /* |
| * If we need a large contiguous chunk of memory, or have |
| * trouble getting a small set of contiguous pages, we |
| * will reclaim both active and inactive pages. |
| * |
| * We use the same threshold as pageout congestion_wait below. |
| */ |
| if (sc->order > PAGE_ALLOC_COSTLY_ORDER) |
| lumpy_reclaim = 1; |
| else if (sc->order && priority < DEF_PRIORITY - 2) |
| lumpy_reclaim = 1; |
| |
| pagevec_init(&pvec, 1); |
| |
| lru_add_drain(); |
| spin_lock_irq(&zone->lru_lock); |
| do { |
| struct page *page; |
| unsigned long nr_taken; |
| unsigned long nr_scan; |
| unsigned long nr_freed; |
| unsigned long nr_active; |
| unsigned int count[NR_LRU_LISTS] = { 0, }; |
| int mode = lumpy_reclaim ? ISOLATE_BOTH : ISOLATE_INACTIVE; |
| |
| nr_taken = sc->isolate_pages(sc->swap_cluster_max, |
| &page_list, &nr_scan, sc->order, mode, |
| zone, sc->mem_cgroup, 0, file); |
| nr_active = clear_active_flags(&page_list, count); |
| __count_vm_events(PGDEACTIVATE, nr_active); |
| |
| __mod_zone_page_state(zone, NR_ACTIVE_FILE, |
| -count[LRU_ACTIVE_FILE]); |
| __mod_zone_page_state(zone, NR_INACTIVE_FILE, |
| -count[LRU_INACTIVE_FILE]); |
| __mod_zone_page_state(zone, NR_ACTIVE_ANON, |
| -count[LRU_ACTIVE_ANON]); |
| __mod_zone_page_state(zone, NR_INACTIVE_ANON, |
| -count[LRU_INACTIVE_ANON]); |
| |
| if (scanning_global_lru(sc)) |
| zone->pages_scanned += nr_scan; |
| |
| reclaim_stat->recent_scanned[0] += count[LRU_INACTIVE_ANON]; |
| reclaim_stat->recent_scanned[0] += count[LRU_ACTIVE_ANON]; |
| reclaim_stat->recent_scanned[1] += count[LRU_INACTIVE_FILE]; |
| reclaim_stat->recent_scanned[1] += count[LRU_ACTIVE_FILE]; |
| |
| spin_unlock_irq(&zone->lru_lock); |
| |
| nr_scanned += nr_scan; |
| nr_freed = shrink_page_list(&page_list, sc, PAGEOUT_IO_ASYNC); |
| |
| /* |
| * If we are direct reclaiming for contiguous pages and we do |
| * not reclaim everything in the list, try again and wait |
| * for IO to complete. This will stall high-order allocations |
| * but that should be acceptable to the caller |
| */ |
| if (nr_freed < nr_taken && !current_is_kswapd() && |
| lumpy_reclaim) { |
| congestion_wait(WRITE, HZ/10); |
| |
| /* |
| * The attempt at page out may have made some |
| * of the pages active, mark them inactive again. |
| */ |
| nr_active = clear_active_flags(&page_list, count); |
| count_vm_events(PGDEACTIVATE, nr_active); |
| |
| nr_freed += shrink_page_list(&page_list, sc, |
| PAGEOUT_IO_SYNC); |
| } |
| |
| nr_reclaimed += nr_freed; |
| local_irq_disable(); |
| if (current_is_kswapd()) { |
| __count_zone_vm_events(PGSCAN_KSWAPD, zone, nr_scan); |
| __count_vm_events(KSWAPD_STEAL, nr_freed); |
| } else if (scanning_global_lru(sc)) |
| __count_zone_vm_events(PGSCAN_DIRECT, zone, nr_scan); |
| |
| __count_zone_vm_events(PGSTEAL, zone, nr_freed); |
| |
| if (nr_taken == 0) |
| goto done; |
| |
| spin_lock(&zone->lru_lock); |
| /* |
| * Put back any unfreeable pages. |
| */ |
| while (!list_empty(&page_list)) { |
| int lru; |
| page = lru_to_page(&page_list); |
| VM_BUG_ON(PageLRU(page)); |
| list_del(&page->lru); |
| if (unlikely(!page_evictable(page, NULL))) { |
| spin_unlock_irq(&zone->lru_lock); |
| putback_lru_page(page); |
| spin_lock_irq(&zone->lru_lock); |
| continue; |
| } |
| SetPageLRU(page); |
| lru = page_lru(page); |
| add_page_to_lru_list(zone, page, lru); |
| if (PageActive(page)) { |
| int file = !!page_is_file_cache(page); |
| reclaim_stat->recent_rotated[file]++; |
| } |
| if (!pagevec_add(&pvec, page)) { |
| spin_unlock_irq(&zone->lru_lock); |
| __pagevec_release(&pvec); |
| spin_lock_irq(&zone->lru_lock); |
| } |
| } |
| } while (nr_scanned < max_scan); |
| spin_unlock(&zone->lru_lock); |
| done: |
| local_irq_enable(); |
| pagevec_release(&pvec); |
| return nr_reclaimed; |
| } |
| |
| /* |
| * We are about to scan this zone at a certain priority level. If that priority |
| * level is smaller (ie: more urgent) than the previous priority, then note |
| * that priority level within the zone. This is done so that when the next |
| * process comes in to scan this zone, it will immediately start out at this |
| * priority level rather than having to build up its own scanning priority. |
| * Here, this priority affects only the reclaim-mapped threshold. |
| */ |
| static inline void note_zone_scanning_priority(struct zone *zone, int priority) |
| { |
| if (priority < zone->prev_priority) |
| zone->prev_priority = priority; |
| } |
| |
| /* |
| * 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 shrink_active_list(unsigned long nr_pages, struct zone *zone, |
| struct scan_control *sc, int priority, int file) |
| { |
| unsigned long pgmoved; |
| unsigned long pgscanned; |
| LIST_HEAD(l_hold); /* The pages which were snipped off */ |
| LIST_HEAD(l_inactive); |
| struct page *page; |
| struct pagevec pvec; |
| enum lru_list lru; |
| struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); |
| |
| lru_add_drain(); |
| spin_lock_irq(&zone->lru_lock); |
| pgmoved = sc->isolate_pages(nr_pages, &l_hold, &pgscanned, sc->order, |
| ISOLATE_ACTIVE, zone, |
| sc->mem_cgroup, 1, file); |
| /* |
| * zone->pages_scanned is used for detect zone's oom |
| * mem_cgroup remembers nr_scan by itself. |
| */ |
| if (scanning_global_lru(sc)) { |
| zone->pages_scanned += pgscanned; |
| } |
| reclaim_stat->recent_scanned[!!file] += pgmoved; |
| |
| if (file) |
| __mod_zone_page_state(zone, NR_ACTIVE_FILE, -pgmoved); |
| else |
| __mod_zone_page_state(zone, NR_ACTIVE_ANON, -pgmoved); |
| spin_unlock_irq(&zone->lru_lock); |
| |
| pgmoved = 0; /* count referenced (mapping) mapped pages */ |
| while (!list_empty(&l_hold)) { |
| cond_resched(); |
| page = lru_to_page(&l_hold); |
| list_del(&page->lru); |
| |
| if (unlikely(!page_evictable(page, NULL))) { |
| putback_lru_page(page); |
| continue; |
| } |
| |
| /* page_referenced clears PageReferenced */ |
| if (page_mapping_inuse(page) && |
| page_referenced(page, 0, sc->mem_cgroup)) |
| pgmoved++; |
| |
| list_add(&page->lru, &l_inactive); |
| } |
| |
| /* |
| * Move the pages to the [file or anon] inactive list. |
| */ |
| pagevec_init(&pvec, 1); |
| lru = LRU_BASE + file * LRU_FILE; |
| |
| spin_lock_irq(&zone->lru_lock); |
| /* |
| * Count referenced pages from currently used mappings as |
| * rotated, even though they are moved to the inactive list. |
| * This helps balance scan pressure between file and anonymous |
| * pages in get_scan_ratio. |
| */ |
| reclaim_stat->recent_rotated[!!file] += pgmoved; |
| |
| pgmoved = 0; /* count pages moved to inactive list */ |
| while (!list_empty(&l_inactive)) { |
| page = lru_to_page(&l_inactive); |
| prefetchw_prev_lru_page(page, &l_inactive, flags); |
| VM_BUG_ON(PageLRU(page)); |
| SetPageLRU(page); |
| VM_BUG_ON(!PageActive(page)); |
| ClearPageActive(page); |
| |
| list_move(&page->lru, &zone->lru[lru].list); |
| mem_cgroup_add_lru_list(page, lru); |
| pgmoved++; |
| if (!pagevec_add(&pvec, page)) { |
| spin_unlock_irq(&zone->lru_lock); |
| if (buffer_heads_over_limit) |
| pagevec_strip(&pvec); |
| __pagevec_release(&pvec); |
| spin_lock_irq(&zone->lru_lock); |
| } |
| } |
| __mod_zone_page_state(zone, NR_LRU_BASE + lru, pgmoved); |
| __count_zone_vm_events(PGREFILL, zone, pgscanned); |
| __count_vm_events(PGDEACTIVATE, pgmoved); |
| spin_unlock_irq(&zone->lru_lock); |
| if (buffer_heads_over_limit) |
| pagevec_strip(&pvec); |
| pagevec_release(&pvec); |
| } |
| |
| static int inactive_anon_is_low_global(struct zone *zone) |
| { |
| unsigned long active, inactive; |
| |
| active = zone_page_state(zone, NR_ACTIVE_ANON); |
| inactive = zone_page_state(zone, NR_INACTIVE_ANON); |
| |
| if (inactive * zone->inactive_ratio < active) |
| return 1; |
| |
| return 0; |
| } |
| |
| /** |
| * inactive_anon_is_low - check if anonymous pages need to be deactivated |
| * @zone: zone to check |
| * @sc: scan control of this context |
| * |
| * Returns true if the zone does not have enough inactive anon pages, |
| * meaning some active anon pages need to be deactivated. |
| */ |
| static int inactive_anon_is_low(struct zone *zone, struct scan_control *sc) |
| { |
| int low; |
| |
| if (scanning_global_lru(sc)) |
| low = inactive_anon_is_low_global(zone); |
| else |
| low = mem_cgroup_inactive_anon_is_low(sc->mem_cgroup); |
| return low; |
| } |
| |
| static int inactive_file_is_low_global(struct zone *zone) |
| { |
| unsigned long active, inactive; |
| |
| active = zone_page_state(zone, NR_ACTIVE_FILE); |
| inactive = zone_page_state(zone, NR_INACTIVE_FILE); |
| |
| return (active > inactive); |
| } |
| |
| /** |
| * inactive_file_is_low - check if file pages need to be deactivated |
| * @zone: zone to check |
| * @sc: scan control of this context |
| * |
| * When the system is doing streaming IO, memory pressure here |
| * ensures that active file pages get deactivated, until more |
| * than half of the file pages are on the inactive list. |
| * |
| * Once we get to that situation, protect the system's working |
| * set from being evicted by disabling active file page aging. |
| * |
| * This uses a different ratio than the anonymous pages, because |
| * the page cache uses a use-once replacement algorithm. |
| */ |
| static int inactive_file_is_low(struct zone *zone, struct scan_control *sc) |
| { |
| int low; |
| |
| if (scanning_global_lru(sc)) |
| low = inactive_file_is_low_global(zone); |
| else |
| low = mem_cgroup_inactive_file_is_low(sc->mem_cgroup); |
| return low; |
| } |
| |
| static unsigned long shrink_list(enum lru_list lru, unsigned long nr_to_scan, |
| struct zone *zone, struct scan_control *sc, int priority) |
| { |
| int file = is_file_lru(lru); |
| |
| if (lru == LRU_ACTIVE_FILE && inactive_file_is_low(zone, sc)) { |
| shrink_active_list(nr_to_scan, zone, sc, priority, file); |
| return 0; |
| } |
| |
| if (lru == LRU_ACTIVE_ANON && inactive_anon_is_low(zone, sc)) { |
| shrink_active_list(nr_to_scan, zone, sc, priority, file); |
| return 0; |
| } |
| return shrink_inactive_list(nr_to_scan, zone, sc, priority, file); |
| } |
| |
| /* |
| * Determine how aggressively the anon and file LRU lists should be |
| * scanned. The relative value of each set of LRU lists is determined |
| * by looking at the fraction of the pages scanned we did rotate back |
| * onto the active list instead of evict. |
| * |
| * percent[0] specifies how much pressure to put on ram/swap backed |
| * memory, while percent[1] determines pressure on the file LRUs. |
| */ |
| static void get_scan_ratio(struct zone *zone, struct scan_control *sc, |
| unsigned long *percent) |
| { |
| unsigned long anon, file, free; |
| unsigned long anon_prio, file_prio; |
| unsigned long ap, fp; |
| struct zone_reclaim_stat *reclaim_stat = get_reclaim_stat(zone, sc); |
| |
| /* If we have no swap space, do not bother scanning anon pages. */ |
| if (!sc->may_swap || (nr_swap_pages <= 0)) { |
| percent[0] = 0; |
| percent[1] = 100; |
| return; |
| } |
| |
| anon = zone_nr_pages(zone, sc, LRU_ACTIVE_ANON) + |
| zone_nr_pages(zone, sc, LRU_INACTIVE_ANON); |
| file = zone_nr_pages(zone, sc, LRU_ACTIVE_FILE) + |
| zone_nr_pages(zone, sc, LRU_INACTIVE_FILE); |
| |
| if (scanning_global_lru(sc)) { |
| free = zone_page_state(zone, NR_FREE_PAGES); |
| /* If we have very few page cache pages, |
| force-scan anon pages. */ |
| if (unlikely(file + free <= high_wmark_pages(zone))) { |
| percent[0] = 100; |
| percent[1] = 0; |
| return; |
| } |
| } |
| |
| /* |
| * 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] |
| */ |
| if (unlikely(reclaim_stat->recent_scanned[0] > anon / 4)) { |
| spin_lock_irq(&zone->lru_lock); |
| reclaim_stat->recent_scanned[0] /= 2; |
| reclaim_stat->recent_rotated[0] /= 2; |
| spin_unlock_irq(&zone->lru_lock); |
| } |
| |
| if (unlikely(reclaim_stat->recent_scanned[1] > file / 4)) { |
| spin_lock_irq(&zone->lru_lock); |
| reclaim_stat->recent_scanned[1] /= 2; |
| reclaim_stat->recent_rotated[1] /= 2; |
| spin_unlock_irq(&zone->lru_lock); |
| } |
| |
| /* |
| * With swappiness at 100, anonymous and file have the same priority. |
| * This scanning priority is essentially the inverse of IO cost. |
| */ |
| anon_prio = sc->swappiness; |
| file_prio = 200 - sc->swappiness; |
| |
| /* |
| * The amount of pressure on anon vs file pages is inversely |
| * proportional to the fraction of recently scanned pages on |
| * each list that were recently referenced and in active use. |
| */ |
| ap = (anon_prio + 1) * (reclaim_stat->recent_scanned[0] + 1); |
| ap /= reclaim_stat->recent_rotated[0] + 1; |
| |
| fp = (file_prio + 1) * (reclaim_stat->recent_scanned[1] + 1); |
| fp /= reclaim_stat->recent_rotated[1] + 1; |
| |
| /* Normalize to percentages */ |
| percent[0] = 100 * ap / (ap + fp + 1); |
| percent[1] = 100 - percent[0]; |
| } |
| |
| /* |
| * Smallish @nr_to_scan's are deposited in @nr_saved_scan, |
| * until we collected @swap_cluster_max pages to scan. |
| */ |
| static unsigned long nr_scan_try_batch(unsigned long nr_to_scan, |
| unsigned long *nr_saved_scan, |
| unsigned long swap_cluster_max) |
| { |
| unsigned long nr; |
| |
| *nr_saved_scan += nr_to_scan; |
| nr = *nr_saved_scan; |
| |
| if (nr >= swap_cluster_max) |
| *nr_saved_scan = 0; |
| else |
| nr = 0; |
| |
| return nr; |
| } |
| |
| /* |
| * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. |
| */ |
| static void shrink_zone(int priority, struct zone *zone, |
| struct scan_control *sc) |
| { |
| unsigned long nr[NR_LRU_LISTS]; |
| unsigned long nr_to_scan; |
| unsigned long percent[2]; /* anon @ 0; file @ 1 */ |
| enum lru_list l; |
| unsigned long nr_reclaimed = sc->nr_reclaimed; |
| unsigned long swap_cluster_max = sc->swap_cluster_max; |
| |
| get_scan_ratio(zone, sc, percent); |
| |
| for_each_evictable_lru(l) { |
| int file = is_file_lru(l); |
| unsigned long scan; |
| |
| scan = zone_nr_pages(zone, sc, l); |
| if (priority) { |
| scan >>= priority; |
| scan = (scan * percent[file]) / 100; |
| } |
| if (scanning_global_lru(sc)) |
| nr[l] = nr_scan_try_batch(scan, |
| &zone->lru[l].nr_saved_scan, |
| swap_cluster_max); |
| else |
| nr[l] = scan; |
| } |
| |
| while (nr[LRU_INACTIVE_ANON] || nr[LRU_ACTIVE_FILE] || |
| nr[LRU_INACTIVE_FILE]) { |
| for_each_evictable_lru(l) { |
| if (nr[l]) { |
| nr_to_scan = min(nr[l], swap_cluster_max); |
| nr[l] -= nr_to_scan; |
| |
| nr_reclaimed += shrink_list(l, nr_to_scan, |
| zone, sc, priority); |
| } |
| } |
| /* |
| * On large memory systems, scan >> priority can become |
| * really large. This is fine for the starting priority; |
| * we want to put equal scanning pressure on each zone. |
| * However, if the VM has a harder time of freeing pages, |
| * with multiple processes reclaiming pages, the total |
| * freeing target can get unreasonably large. |
| */ |
| if (nr_reclaimed > swap_cluster_max && |
| priority < DEF_PRIORITY && !current_is_kswapd()) |
| break; |
| } |
| |
| sc->nr_reclaimed = nr_reclaimed; |
| |
| /* |
| * Even if we did not try to evict anon pages at all, we want to |
| * rebalance the anon lru active/inactive ratio. |
| */ |
| if (inactive_anon_is_low(zone, sc) && nr_swap_pages > 0) |
| shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0); |
| |
| throttle_vm_writeout(sc->gfp_mask); |
| } |
| |
| /* |
| * This is the direct reclaim path, for page-allocating processes. We only |
| * try to reclaim pages from zones which will satisfy the caller's allocation |
| * request. |
| * |
| * We reclaim from a zone even if that zone is over high_wmark_pages(zone). |
| * Because: |
| * a) The caller may be trying to free *extra* pages to satisfy a higher-order |
| * allocation or |
| * b) The target zone may be at high_wmark_pages(zone) but the lower zones |
| * must go *over* high_wmark_pages(zone) to satisfy the `incremental min' |
| * zone defense algorithm. |
| * |
| * If a zone is deemed to be full of pinned pages then just give it a light |
| * scan then give up on it. |
| */ |
| static void shrink_zones(int priority, struct zonelist *zonelist, |
| struct scan_control *sc) |
| { |
| enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask); |
| struct zoneref *z; |
| struct zone *zone; |
| |
| sc->all_unreclaimable = 1; |
| for_each_zone_zonelist_nodemask(zone, z, zonelist, high_zoneidx, |
| sc->nodemask) { |
| if (!populated_zone(zone)) |
| continue; |
| /* |
| * Take care memory controller reclaiming has small influence |
| * to global LRU. |
| */ |
| if (scanning_global_lru(sc)) { |
| if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
| continue; |
| note_zone_scanning_priority(zone, priority); |
| |
| if (zone_is_all_unreclaimable(zone) && |
| priority != DEF_PRIORITY) |
| continue; /* Let kswapd poll it */ |
| sc->all_unreclaimable = 0; |
| } else { |
| /* |
| * Ignore cpuset limitation here. We just want to reduce |
| * # of used pages by us regardless of memory shortage. |
| */ |
| sc->all_unreclaimable = 0; |
| mem_cgroup_note_reclaim_priority(sc->mem_cgroup, |
| priority); |
| } |
| |
| shrink_zone(priority, zone, sc); |
| } |
| } |
| |
| /* |
| * 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 pdflush 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) |
| { |
| int priority; |
| unsigned long ret = 0; |
| unsigned long total_scanned = 0; |
| struct reclaim_state *reclaim_state = current->reclaim_state; |
| unsigned long lru_pages = 0; |
| struct zoneref *z; |
| struct zone *zone; |
| enum zone_type high_zoneidx = gfp_zone(sc->gfp_mask); |
| |
| delayacct_freepages_start(); |
| |
| if (scanning_global_lru(sc)) |
| count_vm_event(ALLOCSTALL); |
| /* |
| * mem_cgroup will not do shrink_slab. |
| */ |
| if (scanning_global_lru(sc)) { |
| for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) { |
| |
| if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
| continue; |
| |
| lru_pages += zone_lru_pages(zone); |
| } |
| } |
| |
| for (priority = DEF_PRIORITY; priority >= 0; priority--) { |
| sc->nr_scanned = 0; |
| if (!priority) |
| disable_swap_token(); |
| shrink_zones(priority, zonelist, sc); |
| /* |
| * Don't shrink slabs when reclaiming memory from |
| * over limit cgroups |
| */ |
| if (scanning_global_lru(sc)) { |
| shrink_slab(sc->nr_scanned, sc->gfp_mask, 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->swap_cluster_max) { |
| ret = sc->nr_reclaimed; |
| goto out; |
| } |
| |
| /* |
| * Try to write back as many pages as we just scanned. This |
| * tends to cause slow streaming writers to write data to the |
| * disk smoothly, at the dirtying rate, which is nice. But |
| * that's undesirable in laptop mode, where we *want* lumpy |
| * writeout. So in laptop mode, write out the whole world. |
| */ |
| if (total_scanned > sc->swap_cluster_max + |
| sc->swap_cluster_max / 2) { |
| wakeup_pdflush(laptop_mode ? 0 : total_scanned); |
| sc->may_writepage = 1; |
| } |
| |
| /* Take a nap, wait for some writeback to complete */ |
| if (sc->nr_scanned && priority < DEF_PRIORITY - 2) |
| congestion_wait(WRITE, HZ/10); |
| } |
| /* top priority shrink_zones still had more to do? don't OOM, then */ |
| if (!sc->all_unreclaimable && scanning_global_lru(sc)) |
| ret = sc->nr_reclaimed; |
| out: |
| /* |
| * Now that we've scanned all the zones at this priority level, note |
| * that level within the zone so that the next thread which performs |
| * scanning of this zone will immediately start out at this priority |
| * level. This affects only the decision whether or not to bring |
| * mapped pages onto the inactive list. |
| */ |
| if (priority < 0) |
| priority = 0; |
| |
| if (scanning_global_lru(sc)) { |
| for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) { |
| |
| if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
| continue; |
| |
| zone->prev_priority = priority; |
| } |
| } else |
| mem_cgroup_record_reclaim_priority(sc->mem_cgroup, priority); |
| |
| delayacct_freepages_end(); |
| |
| return ret; |
| } |
| |
| unsigned long try_to_free_pages(struct zonelist *zonelist, int order, |
| gfp_t gfp_mask, nodemask_t *nodemask) |
| { |
| struct scan_control sc = { |
| .gfp_mask = gfp_mask, |
| .may_writepage = !laptop_mode, |
| .swap_cluster_max = SWAP_CLUSTER_MAX, |
| .may_unmap = 1, |
| .may_swap = 1, |
| .swappiness = vm_swappiness, |
| .order = order, |
| .mem_cgroup = NULL, |
| .isolate_pages = isolate_pages_global, |
| .nodemask = nodemask, |
| }; |
| |
| return do_try_to_free_pages(zonelist, &sc); |
| } |
| |
| #ifdef CONFIG_CGROUP_MEM_RES_CTLR |
| |
| unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont, |
| gfp_t gfp_mask, |
| bool noswap, |
| unsigned int swappiness) |
| { |
| struct scan_control sc = { |
| .may_writepage = !laptop_mode, |
| .may_unmap = 1, |
| .may_swap = !noswap, |
| .swap_cluster_max = SWAP_CLUSTER_MAX, |
| .swappiness = swappiness, |
| .order = 0, |
| .mem_cgroup = mem_cont, |
| .isolate_pages = mem_cgroup_isolate_pages, |
| .nodemask = NULL, /* we don't care the placement */ |
| }; |
| struct zonelist *zonelist; |
| |
| sc.gfp_mask = (gfp_mask & GFP_RECLAIM_MASK) | |
| (GFP_HIGHUSER_MOVABLE & ~GFP_RECLAIM_MASK); |
| zonelist = NODE_DATA(numa_node_id())->node_zonelists; |
| return do_try_to_free_pages(zonelist, &sc); |
| } |
| #endif |
| |
| /* |
| * For kswapd, balance_pgdat() will work across all this node's zones until |
| * they are all at high_wmark_pages(zone). |
| * |
| * Returns the number of pages which were actually freed. |
| * |
| * 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 all_zones_ok; |
| int priority; |
| int i; |
| unsigned long total_scanned; |
| struct reclaim_state *reclaim_state = current->reclaim_state; |
| struct scan_control sc = { |
| .gfp_mask = GFP_KERNEL, |
| .may_unmap = 1, |
| .may_swap = 1, |
| .swap_cluster_max = SWAP_CLUSTER_MAX, |
| .swappiness = vm_swappiness, |
| .order = order, |
| .mem_cgroup = NULL, |
| .isolate_pages = isolate_pages_global, |
| }; |
| /* |
| * temp_priority is used to remember the scanning priority at which |
| * this zone was successfully refilled to |
| * free_pages == high_wmark_pages(zone). |
| */ |
| int temp_priority[MAX_NR_ZONES]; |
| |
| loop_again: |
| total_scanned = 0; |
| sc.nr_reclaimed = 0; |
| sc.may_writepage = !laptop_mode; |
| count_vm_event(PAGEOUTRUN); |
| |
| for (i = 0; i < pgdat->nr_zones; i++) |
| temp_priority[i] = DEF_PRIORITY; |
| |
| for (priority = DEF_PRIORITY; priority >= 0; priority--) { |
| int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ |
| unsigned long lru_pages = 0; |
| |
| /* The swap token gets in the way of swapout... */ |
| if (!priority) |
| disable_swap_token(); |
| |
| all_zones_ok = 1; |
| |
| /* |
| * 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_is_all_unreclaimable(zone) && |
| priority != DEF_PRIORITY) |
| continue; |
| |
| /* |
| * Do some background aging of the anon list, to give |
| * pages a chance to be referenced before reclaiming. |
| */ |
| if (inactive_anon_is_low(zone, &sc)) |
| shrink_active_list(SWAP_CLUSTER_MAX, zone, |
| &sc, priority, 0); |
| |
| if (!zone_watermark_ok(zone, order, |
| high_wmark_pages(zone), 0, 0)) { |
| end_zone = i; |
| break; |
| } |
| } |
| if (i < 0) |
| goto out; |
| |
| for (i = 0; i <= end_zone; i++) { |
| struct zone *zone = pgdat->node_zones + i; |
| |
| lru_pages += zone_lru_pages(zone); |
| } |
| |
| /* |
| * Now scan the zone in the dma->highmem direction, stopping |
| * at the last zone which needs scanning. |
| * |
| * We do this because the page allocator works in the opposite |
| * direction. This prevents the page allocator from allocating |
| * pages behind kswapd's direction of progress, which would |
| * cause too much scanning of the lower zones. |
| */ |
| for (i = 0; i <= end_zone; i++) { |
| struct zone *zone = pgdat->node_zones + i; |
| int nr_slab; |
| |
| if (!populated_zone(zone)) |
| continue; |
| |
| if (zone_is_all_unreclaimable(zone) && |
| priority != DEF_PRIORITY) |
| continue; |
| |
| if (!zone_watermark_ok(zone, order, |
| high_wmark_pages(zone), end_zone, 0)) |
| all_zones_ok = 0; |
| temp_priority[i] = priority; |
| sc.nr_scanned = 0; |
| note_zone_scanning_priority(zone, priority); |
| /* |
| * We put equal pressure on every zone, unless one |
| * zone has way too many pages free already. |
| */ |
| if (!zone_watermark_ok(zone, order, |
| 8*high_wmark_pages(zone), end_zone, 0)) |
| shrink_zone(priority, zone, &sc); |
| reclaim_state->reclaimed_slab = 0; |
| nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL, |
| lru_pages); |
| sc.nr_reclaimed += reclaim_state->reclaimed_slab; |
| total_scanned += sc.nr_scanned; |
| if (zone_is_all_unreclaimable(zone)) |
| continue; |
| if (nr_slab == 0 && zone->pages_scanned >= |
| (zone_lru_pages(zone) * 6)) |
| zone_set_flag(zone, |
| ZONE_ALL_UNRECLAIMABLE); |
| /* |
| * If we've done a decent amount of scanning and |
| * the reclaim ratio is low, start doing writepage |
| * even in laptop mode |
| */ |
| if (total_scanned > SWAP_CLUSTER_MAX * 2 && |
| total_scanned > sc.nr_reclaimed + sc.nr_reclaimed / 2) |
| sc.may_writepage = 1; |
| } |
| if (all_zones_ok) |
| break; /* kswapd: all done */ |
| /* |
| * OK, kswapd is getting into trouble. Take a nap, then take |
| * another pass across the zones. |
| */ |
| if (total_scanned && priority < DEF_PRIORITY - 2) |
| congestion_wait(WRITE, HZ/10); |
| |
| /* |
| * We do this so kswapd doesn't build up large priorities for |
| * example when it is freeing in parallel with allocators. It |
| * matches the direct reclaim path behaviour in terms of impact |
| * on zone->*_priority. |
| */ |
| if (sc.nr_reclaimed >= SWAP_CLUSTER_MAX) |
| break; |
| } |
| out: |
| /* |
| * Note within each zone the priority level at which this zone was |
| * brought into a happy state. So that the next thread which scans this |
| * zone will start out at that priority level. |
| */ |
| for (i = 0; i < pgdat->nr_zones; i++) { |
| struct zone *zone = pgdat->node_zones + i; |
| |
| zone->prev_priority = temp_priority[i]; |
| } |
| if (!all_zones_ok) { |
| cond_resched(); |
| |
| try_to_freeze(); |
| |
| /* |
| * Fragmentation may mean that the system cannot be |
| * rebalanced for high-order allocations in all zones. |
| * At this point, if nr_reclaimed < SWAP_CLUSTER_MAX, |
| * it means the zones have been fully scanned and are still |
| * not balanced. For high-order allocations, there is |
| * little point trying all over again as kswapd may |
| * infinite loop. |
| * |
| * Instead, recheck all watermarks at order-0 as they |
| * are the most important. If watermarks are ok, kswapd will go |
| * back to sleep. High-order users can still perform direct |
| * reclaim if they wish. |
| */ |
| if (sc.nr_reclaimed < SWAP_CLUSTER_MAX) |
| order = sc.order = 0; |
| |
| goto loop_again; |
| } |
| |
| return sc.nr_reclaimed; |
| } |
| |
| /* |
| * 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; |
| pg_data_t *pgdat = (pg_data_t*)p; |
| struct task_struct *tsk = current; |
| DEFINE_WAIT(wait); |
| 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 = 0; |
| for ( ; ; ) { |
| unsigned long new_order; |
| |
| prepare_to_wait(&pgdat->kswapd_wait, &wait, TASK_INTERRUPTIBLE); |
| new_order = pgdat->kswapd_max_order; |
| pgdat->kswapd_max_order = 0; |
| if (order < new_order) { |
| /* |
| * Don't sleep if someone wants a larger 'order' |
| * allocation |
| */ |
| order = new_order; |
| } else { |
| if (!freezing(current)) |
| schedule(); |
| |
| order = pgdat->kswapd_max_order; |
| } |
| finish_wait(&pgdat->kswapd_wait, &wait); |
| |
| if (!try_to_freeze()) { |
| /* We can speed up thawing tasks if we don't call |
| * balance_pgdat after returning from the refrigerator |
| */ |
| balance_pgdat(pgdat, order); |
| } |
| } |
| 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) |
| { |
| pg_data_t *pgdat; |
| |
| if (!populated_zone(zone)) |
| return; |
| |
| pgdat = zone->zone_pgdat; |
| if (zone_watermark_ok(zone, order, low_wmark_pages(zone), 0, 0)) |
| return; |
| if (pgdat->kswapd_max_order < order) |
| pgdat->kswapd_max_order = order; |
| if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
| return; |
| if (!waitqueue_active(&pgdat->kswapd_wait)) |
| return; |
| wake_up_interruptible(&pgdat->kswapd_wait); |
| } |
| |
| unsigned long global_lru_pages(void) |
| { |
| return global_page_state(NR_ACTIVE_ANON) |
| + global_page_state(NR_ACTIVE_FILE) |
| + global_page_state(NR_INACTIVE_ANON) |
| + global_page_state(NR_INACTIVE_FILE); |
| } |
| |
| #ifdef CONFIG_HIBERNATION |
| /* |
| * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages |
| * from LRU lists system-wide, for given pass and priority. |
| * |
| * For pass > 3 we also try to shrink the LRU lists that contain a few pages |
| */ |
| static void shrink_all_zones(unsigned long nr_pages, int prio, |
| int pass, struct scan_control *sc) |
| { |
| struct zone *zone; |
| unsigned long nr_reclaimed = 0; |
| |
| for_each_populated_zone(zone) { |
| enum lru_list l; |
| |
| if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY) |
| continue; |
| |
| for_each_evictable_lru(l) { |
| enum zone_stat_item ls = NR_LRU_BASE + l; |
| unsigned long lru_pages = zone_page_state(zone, ls); |
| |
| /* For pass = 0, we don't shrink the active list */ |
| if (pass == 0 && (l == LRU_ACTIVE_ANON || |
| l == LRU_ACTIVE_FILE)) |
| continue; |
| |
| zone->lru[l].nr_saved_scan += (lru_pages >> prio) + 1; |
| if (zone->lru[l].nr_saved_scan >= nr_pages || pass > 3) { |
| unsigned long nr_to_scan; |
| |
| zone->lru[l].nr_saved_scan = 0; |
| nr_to_scan = min(nr_pages, lru_pages); |
| nr_reclaimed += shrink_list(l, nr_to_scan, zone, |
| sc, prio); |
| if (nr_reclaimed >= nr_pages) { |
| sc->nr_reclaimed += nr_reclaimed; |
| return; |
| } |
| } |
| } |
| } |
| sc->nr_reclaimed += nr_reclaimed; |
| } |
| |
| /* |
| * Try to free `nr_pages' 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_pages) |
| { |
| unsigned long lru_pages, nr_slab; |
| int pass; |
| struct reclaim_state reclaim_state; |
| struct scan_control sc = { |
| .gfp_mask = GFP_KERNEL, |
| .may_unmap = 0, |
| .may_writepage = 1, |
| .isolate_pages = isolate_pages_global, |
| .nr_reclaimed = 0, |
| }; |
| |
| current->reclaim_state = &reclaim_state; |
| |
| lru_pages = global_lru_pages(); |
| nr_slab = global_page_state(NR_SLAB_RECLAIMABLE); |
| /* If slab caches are huge, it's better to hit them first */ |
| while (nr_slab >= lru_pages) { |
| reclaim_state.reclaimed_slab = 0; |
| shrink_slab(nr_pages, sc.gfp_mask, lru_pages); |
| if (!reclaim_state.reclaimed_slab) |
| break; |
| |
| sc.nr_reclaimed += reclaim_state.reclaimed_slab; |
| if (sc.nr_reclaimed >= nr_pages) |
| goto out; |
| |
| nr_slab -= reclaim_state.reclaimed_slab; |
| } |
| |
| /* |
| * We try to shrink LRUs in 5 passes: |
| * 0 = Reclaim from inactive_list only |
| * 1 = Reclaim from active list but don't reclaim mapped |
| * 2 = 2nd pass of type 1 |
| * 3 = Reclaim mapped (normal reclaim) |
| * 4 = 2nd pass of type 3 |
| */ |
| for (pass = 0; pass < 5; pass++) { |
| int prio; |
| |
| /* Force reclaiming mapped pages in the passes #3 and #4 */ |
| if (pass > 2) |
| sc.may_unmap = 1; |
| |
| for (prio = DEF_PRIORITY; prio >= 0; prio--) { |
| unsigned long nr_to_scan = nr_pages - sc.nr_reclaimed; |
| |
| sc.nr_scanned = 0; |
| sc.swap_cluster_max = nr_to_scan; |
| shrink_all_zones(nr_to_scan, prio, pass, &sc); |
| if (sc.nr_reclaimed >= nr_pages) |
| goto out; |
| |
| reclaim_state.reclaimed_slab = 0; |
| shrink_slab(sc.nr_scanned, sc.gfp_mask, |
| global_lru_pages()); |
| sc.nr_reclaimed += reclaim_state.reclaimed_slab; |
| if (sc.nr_reclaimed >= nr_pages) |
| goto out; |
| |
| if (sc.nr_scanned && prio < DEF_PRIORITY - 2) |
| congestion_wait(WRITE, HZ / 10); |
| } |
| } |
| |
| /* |
| * If sc.nr_reclaimed = 0, we could not shrink LRUs, but there may be |
| * something in slab caches |
| */ |
| if (!sc.nr_reclaimed) { |
| do { |
| reclaim_state.reclaimed_slab = 0; |
| shrink_slab(nr_pages, sc.gfp_mask, global_lru_pages()); |
| sc.nr_reclaimed += reclaim_state.reclaimed_slab; |
| } while (sc.nr_reclaimed < nr_pages && |
| reclaim_state.reclaimed_slab > 0); |
| } |
| |
| |
| out: |
| current->reclaim_state = NULL; |
| |
| return sc.nr_reclaimed; |
| } |
| #endif /* CONFIG_HIBERNATION */ |
| |
| /* It's optimal to keep kswapds on the same CPUs as their memory, but |
| not required for correctness. So if the last cpu in a node goes |
| away, we get changed to run anywhere: as the first one comes back, |
| restore their cpu bindings. */ |
| static int __devinit cpu_callback(struct notifier_block *nfb, |
| unsigned long action, void *hcpu) |
| { |
| int nid; |
| |
| if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { |
| for_each_node_state(nid, N_HIGH_MEMORY) { |
| pg_data_t *pgdat = NODE_DATA(nid); |
| const struct cpumask *mask; |
| |
| mask = cpumask_of_node(pgdat->node_id); |
| |
| if (cpumask_any_and(cpu_online_mask, mask) < nr_cpu_ids) |
| /* One of our CPUs online: restore mask */ |
| set_cpus_allowed_ptr(pgdat->kswapd, mask); |
| } |
| } |
| return NOTIFY_OK; |
| } |
| |
| /* |
| * This kswapd start function will be called by init and node-hot-add. |
| * On node-hot-add, kswapd will moved to proper cpus if cpus are hot-added. |
| */ |
| int kswapd_run(int nid) |
| { |
| pg_data_t *pgdat = NODE_DATA(nid); |
| int ret = 0; |
| |
| if (pgdat->kswapd) |
| return 0; |
| |
| pgdat->kswapd = kthread_run(kswapd, pgdat, "kswapd%d", nid); |
| if (IS_ERR(pgdat->kswapd)) { |
| /* failure at boot is fatal */ |
| BUG_ON(system_state == SYSTEM_BOOTING); |
| printk("Failed to start kswapd on node %d\n",nid); |
| ret = -1; |
| } |
| return ret; |
| } |
| |
| static int __init kswapd_init(void) |
| { |
| int nid; |
| |
| swap_setup(); |
| for_each_node_state(nid, N_HIGH_MEMORY) |
| kswapd_run(nid); |
| hotcpu_notifier(cpu_callback, 0); |
| return 0; |
| } |
| |
| module_init(kswapd_init) |
| |
| #ifdef CONFIG_NUMA |
| /* |
| * Zone reclaim mode |
| * |
| * If non-zero call zone_reclaim when the number of free pages falls below |
| * the watermarks. |
| */ |
| int zone_reclaim_mode __read_mostly; |
| |
| #define RECLAIM_OFF 0 |
| #define RECLAIM_ZONE (1<<0) /* Run shrink_inactive_list on the zone */ |
| #define RECLAIM_WRITE (1<<1) /* Writeout pages during reclaim */ |
| #define RECLAIM_SWAP (1<<2) /* Swap pages out during reclaim */ |
| |
| /* |
| * Priority for ZONE_RECLAIM. This determines the fraction of pages |
| * of a node considered for each zone_reclaim. 4 scans 1/16th of |
| * a zone. |
| */ |
| #define ZONE_RECLAIM_PRIORITY 4 |
| |
| /* |
| * Percentage of pages in a zone that must be unmapped for zone_reclaim to |
| * occur. |
| */ |
| int sysctl_min_unmapped_ratio = 1; |
| |
| /* |
| * If the number of slab pages in a zone grows beyond this percentage then |
| * slab reclaim needs to occur. |
| */ |
| int sysctl_min_slab_ratio = 5; |
| |
| /* |
| * Try to free up some pages from this zone through reclaim. |
| */ |
| static int __zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) |
| { |
| /* Minimum pages needed in order to stay on node */ |
| const unsigned long nr_pages = 1 << order; |
| struct task_struct *p = current; |
| struct reclaim_state reclaim_state; |
| int priority; |
| struct scan_control sc = { |
| .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), |
| .may_unmap = !!(zone_reclaim_mode & RECLAIM_SWAP), |
| .may_swap = 1, |
| .swap_cluster_max = max_t(unsigned long, nr_pages, |
| SWAP_CLUSTER_MAX), |
| .gfp_mask = gfp_mask, |
| .swappiness = vm_swappiness, |
| .order = order, |
| .isolate_pages = isolate_pages_global, |
| }; |
| unsigned long slab_reclaimable; |
| |
| disable_swap_token(); |
| 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; |
| reclaim_state.reclaimed_slab = 0; |
| p->reclaim_state = &reclaim_state; |
| |
| if (zone_page_state(zone, NR_FILE_PAGES) - |
| zone_page_state(zone, NR_FILE_MAPPED) > |
| zone->min_unmapped_pages) { |
| /* |
| * Free memory by calling shrink zone with increasing |
| * priorities until we have enough memory freed. |
| */ |
| priority = ZONE_RECLAIM_PRIORITY; |
| do { |
| note_zone_scanning_priority(zone, priority); |
| shrink_zone(priority, zone, &sc); |
| priority--; |
| } while (priority >= 0 && sc.nr_reclaimed < nr_pages); |
| } |
| |
| slab_reclaimable = zone_page_state(zone, NR_SLAB_RECLAIMABLE); |
| if (slab_reclaimable > 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. |
| */ |
| while (shrink_slab(sc.nr_scanned, gfp_mask, order) && |
| zone_page_state(zone, NR_SLAB_RECLAIMABLE) > |
| slab_reclaimable - nr_pages) |
| ; |
| |
| /* |
| * Update nr_reclaimed by the number of slab pages we |
| * reclaimed from this zone. |
| */ |
| sc.nr_reclaimed += slab_reclaimable - |
| zone_page_state(zone, NR_SLAB_RECLAIMABLE); |
| } |
| |
| p->reclaim_state = NULL; |
| current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); |
| 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_page_state(zone, NR_FILE_PAGES) - |
| zone_page_state(zone, NR_FILE_MAPPED) <= zone->min_unmapped_pages |
| && zone_page_state(zone, NR_SLAB_RECLAIMABLE) |
| <= zone->min_slab_pages) |
| return 0; |
| |
| if (zone_is_all_unreclaimable(zone)) |
| return 0; |
| |
| /* |
| * Do not scan if the allocation should not be delayed. |
| */ |
| if (!(gfp_mask & __GFP_WAIT) || (current->flags & PF_MEMALLOC)) |
| return 0; |
| |
| /* |
| * 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 0; |
| |
| if (zone_test_and_set_flag(zone, ZONE_RECLAIM_LOCKED)) |
| return 0; |
| ret = __zone_reclaim(zone, gfp_mask, order); |
| zone_clear_flag(zone, ZONE_RECLAIM_LOCKED); |
| |
| return ret; |
| } |
| #endif |
| |
| /* |
| * page_evictable - test whether a page is evictable |
| * @page: the page to test |
| * @vma: the VMA in which the page is or will be mapped, may be NULL |
| * |
| * Test whether page is evictable--i.e., should be placed on active/inactive |
| * lists vs unevictable list. The vma argument is !NULL when called from the |
| * fault path to determine how to instantate a new page. |
| * |
| * Reasons page might not be evictable: |
| * (1) page's mapping marked unevictable |
| * (2) page is part of an mlocked VMA |
| * |
| */ |
| int page_evictable(struct page *page, struct vm_area_struct *vma) |
| { |
| |
| if (mapping_unevictable(page_mapping(page))) |
| return 0; |
| |
| if (PageMlocked(page) || (vma && is_mlocked_vma(vma, page))) |
| return 0; |
| |
| return 1; |
| } |
| |
| /** |
| * check_move_unevictable_page - check page for evictability and move to appropriate zone lru list |
| * @page: page to check evictability and move to appropriate lru list |
| * @zone: zone page is in |
| * |
| * Checks a page for evictability and moves the page to the appropriate |
| * zone lru list. |
| * |
| * Restrictions: zone->lru_lock must be held, page must be on LRU and must |
| * have PageUnevictable set. |
| */ |
| static void check_move_unevictable_page(struct page *page, struct zone *zone) |
| { |
| VM_BUG_ON(PageActive(page)); |
| |
| retry: |
| ClearPageUnevictable(page); |
| if (page_evictable(page, NULL)) { |
| enum lru_list l = LRU_INACTIVE_ANON + page_is_file_cache(page); |
| |
| __dec_zone_state(zone, NR_UNEVICTABLE); |
| list_move(&page->lru, &zone->lru[l].list); |
| mem_cgroup_move_lists(page, LRU_UNEVICTABLE, l); |
| __inc_zone_state(zone, NR_INACTIVE_ANON + l); |
| __count_vm_event(UNEVICTABLE_PGRESCUED); |
| } else { |
| /* |
| * rotate unevictable list |
| */ |
| SetPageUnevictable(page); |
| list_move(&page->lru, &zone->lru[LRU_UNEVICTABLE].list); |
| mem_cgroup_rotate_lru_list(page, LRU_UNEVICTABLE); |
| if (page_evictable(page, NULL)) |
| goto retry; |
| } |
| } |
| |
| /** |
| * scan_mapping_unevictable_pages - scan an address space for evictable pages |
| * @mapping: struct address_space to scan for evictable pages |
| * |
| * Scan all pages in mapping. Check unevictable pages for |
| * evictability and move them to the appropriate zone lru list. |
| */ |
| void scan_mapping_unevictable_pages(struct address_space *mapping) |
| { |
| pgoff_t next = 0; |
| pgoff_t end = (i_size_read(mapping->host) + PAGE_CACHE_SIZE - 1) >> |
| PAGE_CACHE_SHIFT; |
| struct zone *zone; |
| struct pagevec pvec; |
| |
| if (mapping->nrpages == 0) |
| return; |
| |
| pagevec_init(&pvec, 0); |
| while (next < end && |
| pagevec_lookup(&pvec, mapping, next, PAGEVEC_SIZE)) { |
| int i; |
| int pg_scanned = 0; |
| |
| zone = NULL; |
| |
| for (i = 0; i < pagevec_count(&pvec); i++) { |
| struct page *page = pvec.pages[i]; |
| pgoff_t page_index = page->index; |
| struct zone *pagezone = page_zone(page); |
| |
| pg_scanned++; |
| if (page_index > next) |
| next = page_index; |
| next++; |
| |
| if (pagezone != zone) { |
| if (zone) |
| spin_unlock_irq(&zone->lru_lock); |
| zone = pagezone; |
| spin_lock_irq(&zone->lru_lock); |
| } |
| |
| if (PageLRU(page) && PageUnevictable(page)) |
| check_move_unevictable_page(page, zone); |
| } |
| if (zone) |
| spin_unlock_irq(&zone->lru_lock); |
| pagevec_release(&pvec); |
| |
| count_vm_events(UNEVICTABLE_PGSCANNED, pg_scanned); |
| } |
| |
| } |
| |
| /** |
| * scan_zone_unevictable_pages - check unevictable list for evictable pages |
| * @zone - zone of which to scan the unevictable list |
| * |
| * Scan @zone's unevictable LRU lists to check for pages that have become |
| * evictable. Move those that have to @zone's inactive list where they |
| * become candidates for reclaim, unless shrink_inactive_zone() decides |
| * to reactivate them. Pages that are still unevictable are rotated |
| * back onto @zone's unevictable list. |
| */ |
| #define SCAN_UNEVICTABLE_BATCH_SIZE 16UL /* arbitrary lock hold batch size */ |
| static void scan_zone_unevictable_pages(struct zone *zone) |
| { |
| struct list_head *l_unevictable = &zone->lru[LRU_UNEVICTABLE].list; |
| unsigned long scan; |
| unsigned long nr_to_scan = zone_page_state(zone, NR_UNEVICTABLE); |
| |
| while (nr_to_scan > 0) { |
| unsigned long batch_size = min(nr_to_scan, |
| SCAN_UNEVICTABLE_BATCH_SIZE); |
| |
| spin_lock_irq(&zone->lru_lock); |
| for (scan = 0; scan < batch_size; scan++) { |
| struct page *page = lru_to_page(l_unevictable); |
| |
| if (!trylock_page(page)) |
| continue; |
| |
| prefetchw_prev_lru_page(page, l_unevictable, flags); |
| |
| if (likely(PageLRU(page) && PageUnevictable(page))) |
| check_move_unevictable_page(page, zone); |
| |
| unlock_page(page); |
| } |
| spin_unlock_irq(&zone->lru_lock); |
| |
| nr_to_scan -= batch_size; |
| } |
| } |
| |
| |
| /** |
| * scan_all_zones_unevictable_pages - scan all unevictable lists for evictable pages |
| * |
| * A really big hammer: scan all zones' unevictable LRU lists to check for |
| * pages that have become evictable. Move those back to the zones' |
| * inactive list where they become candidates for reclaim. |
| * This occurs when, e.g., we have unswappable pages on the unevictable lists, |
| * and we add swap to the system. As such, it runs in the context of a task |
| * that has possibly/probably made some previously unevictable pages |
| * evictable. |
| */ |
| static void scan_all_zones_unevictable_pages(void) |
| { |
| struct zone *zone; |
| |
| for_each_zone(zone) { |
| scan_zone_unevictable_pages(zone); |
| } |
| } |
| |
| /* |
| * scan_unevictable_pages [vm] sysctl handler. On demand re-scan of |
| * all nodes' unevictable lists for evictable pages |
| */ |
| unsigned long scan_unevictable_pages; |
| |
| int scan_unevictable_handler(struct ctl_table *table, int write, |
| struct file *file, void __user *buffer, |
| size_t *length, loff_t *ppos) |
| { |
| proc_doulongvec_minmax(table, write, file, buffer, length, ppos); |
| |
| if (write && *(unsigned long *)table->data) |
| scan_all_zones_unevictable_pages(); |
| |
| scan_unevictable_pages = 0; |
| return 0; |
| } |
| |
| /* |
| * per node 'scan_unevictable_pages' attribute. On demand re-scan of |
| * a specified node's per zone unevictable lists for evictable pages. |
| */ |
| |
| static ssize_t read_scan_unevictable_node(struct sys_device *dev, |
| struct sysdev_attribute *attr, |
| char *buf) |
| { |
| return sprintf(buf, "0\n"); /* always zero; should fit... */ |
| } |
| |
| static ssize_t write_scan_unevictable_node(struct sys_device *dev, |
| struct sysdev_attribute *attr, |
| const char *buf, size_t count) |
| { |
| struct zone *node_zones = NODE_DATA(dev->id)->node_zones; |
| struct zone *zone; |
| unsigned long res; |
| unsigned long req = strict_strtoul(buf, 10, &res); |
| |
| if (!req) |
| return 1; /* zero is no-op */ |
| |
| for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) { |
| if (!populated_zone(zone)) |
| continue; |
| scan_zone_unevictable_pages(zone); |
| } |
| return 1; |
| } |
| |
| |
| static SYSDEV_ATTR(scan_unevictable_pages, S_IRUGO | S_IWUSR, |
| read_scan_unevictable_node, |
| write_scan_unevictable_node); |
| |
| int scan_unevictable_register_node(struct node *node) |
| { |
| return sysdev_create_file(&node->sysdev, &attr_scan_unevictable_pages); |
| } |
| |
| void scan_unevictable_unregister_node(struct node *node) |
| { |
| sysdev_remove_file(&node->sysdev, &attr_scan_unevictable_pages); |
| } |
| |