| /* |
| * 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 <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; |
| |
| /* This context's GFP mask */ |
| gfp_t gfp_mask; |
| |
| int may_writepage; |
| |
| /* 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; |
| |
| /* |
| * Pages that have (or should have) IO pending. If we run into |
| * a lot of these, we're better off waiting a little for IO to |
| * finish rather than scanning more pages in the VM. |
| */ |
| int nr_io_pages; |
| |
| /* Which cgroup do we reclaim from */ |
| struct mem_cgroup *mem_cgroup; |
| |
| /* 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); |
| }; |
| |
| #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); |
| |
| /* |
| * 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 "%s: nr=%ld\n", |
| __FUNCTION__, 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) - !!PagePrivate(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 (PagePrivate(page)) { |
| if (try_to_free_buffers(page)) { |
| ClearPageDirty(page); |
| printk("%s: orphaned page\n", __FUNCTION__); |
| 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; |
| } |
| |
| /* |
| * 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) |
| { |
| BUG_ON(!PageLocked(page)); |
| BUG_ON(mapping != page_mapping(page)); |
| |
| write_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 (unlikely(page_count(page) != 2)) |
| goto cannot_free; |
| smp_rmb(); |
| if (unlikely(PageDirty(page))) |
| goto cannot_free; |
| |
| if (PageSwapCache(page)) { |
| swp_entry_t swap = { .val = page_private(page) }; |
| __delete_from_swap_cache(page); |
| write_unlock_irq(&mapping->tree_lock); |
| swap_free(swap); |
| __put_page(page); /* The pagecache ref */ |
| return 1; |
| } |
| |
| __remove_from_page_cache(page); |
| write_unlock_irq(&mapping->tree_lock); |
| __put_page(page); |
| return 1; |
| |
| cannot_free: |
| write_unlock_irq(&mapping->tree_lock); |
| return 0; |
| } |
| |
| /* |
| * 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 (TestSetPageLocked(page)) |
| goto keep; |
| |
| VM_BUG_ON(PageActive(page)); |
| |
| sc->nr_scanned++; |
| |
| if (!sc->may_swap && 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 { |
| sc->nr_io_pages++; |
| 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; |
| |
| #ifdef CONFIG_SWAP |
| /* |
| * Anonymous process memory has backing store? |
| * Try to allocate it some swap space here. |
| */ |
| if (PageAnon(page) && !PageSwapCache(page)) |
| if (!add_to_swap(page, GFP_ATOMIC)) |
| goto activate_locked; |
| #endif /* CONFIG_SWAP */ |
| |
| 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_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) { |
| sc->nr_io_pages++; |
| 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)) { |
| sc->nr_io_pages++; |
| goto keep; |
| } |
| /* |
| * A synchronous write - probably a ramdisk. Go |
| * ahead and try to reclaim the page. |
| */ |
| if (TestSetPageLocked(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 (PagePrivate(page)) { |
| if (!try_to_release_page(page, sc->gfp_mask)) |
| goto activate_locked; |
| if (!mapping && page_count(page) == 1) |
| goto free_it; |
| } |
| |
| if (!mapping || !remove_mapping(mapping, page)) |
| goto keep_locked; |
| |
| free_it: |
| unlock_page(page); |
| nr_reclaimed++; |
| if (!pagevec_add(&freed_pvec, page)) |
| __pagevec_release_nonlru(&freed_pvec); |
| continue; |
| |
| activate_locked: |
| SetPageActive(page); |
| pgactivate++; |
| keep_locked: |
| unlock_page(page); |
| keep: |
| list_add(&page->lru, &ret_pages); |
| VM_BUG_ON(PageLRU(page)); |
| } |
| list_splice(&ret_pages, page_list); |
| if (pagevec_count(&freed_pvec)) |
| __pagevec_release_nonlru(&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 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; |
| |
| ret = -EBUSY; |
| if (likely(get_page_unless_zero(page))) { |
| /* |
| * Be careful not to clear PageLRU until after we're |
| * sure the page is not being freed elsewhere -- the |
| * page release code relies on it. |
| */ |
| ClearPageLRU(page); |
| ret = 0; |
| } |
| |
| return ret; |
| } |
| |
| /* |
| * zone->lru_lock is heavily contended. Some of the functions that |
| * shrink the lists perform better by taking out a batch of pages |
| * and working on them outside the LRU lock. |
| * |
| * For pagecache intensive workloads, this function is the hottest |
| * spot in the kernel (apart from copy_*_user functions). |
| * |
| * Appropriate locks must be held before calling this function. |
| * |
| * @nr_to_scan: The number of pages to look through on the list. |
| * @src: The LRU list to pull pages off. |
| * @dst: The temp list to put pages on to. |
| * @scanned: The number of pages that were scanned. |
| * @order: The caller's attempted allocation order |
| * @mode: One of the LRU isolation modes |
| * |
| * 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) |
| { |
| 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)) { |
| 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)) { |
| 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; |
| } |
| } |
| } |
| |
| *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) |
| { |
| if (active) |
| return isolate_lru_pages(nr, &z->active_list, dst, |
| scanned, order, mode); |
| else |
| return isolate_lru_pages(nr, &z->inactive_list, dst, |
| scanned, order, mode); |
| } |
| |
| /* |
| * 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) |
| { |
| int nr_active = 0; |
| struct page *page; |
| |
| list_for_each_entry(page, page_list, lru) |
| if (PageActive(page)) { |
| ClearPageActive(page); |
| nr_active++; |
| } |
| |
| return nr_active; |
| } |
| |
| /* |
| * 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) |
| { |
| LIST_HEAD(page_list); |
| struct pagevec pvec; |
| unsigned long nr_scanned = 0; |
| unsigned long nr_reclaimed = 0; |
| |
| 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; |
| |
| nr_taken = sc->isolate_pages(sc->swap_cluster_max, |
| &page_list, &nr_scan, sc->order, |
| (sc->order > PAGE_ALLOC_COSTLY_ORDER)? |
| ISOLATE_BOTH : ISOLATE_INACTIVE, |
| zone, sc->mem_cgroup, 0); |
| nr_active = clear_active_flags(&page_list); |
| __count_vm_events(PGDEACTIVATE, nr_active); |
| |
| __mod_zone_page_state(zone, NR_ACTIVE, -nr_active); |
| __mod_zone_page_state(zone, NR_INACTIVE, |
| -(nr_taken - nr_active)); |
| zone->pages_scanned += nr_scan; |
| 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() && |
| sc->order > PAGE_ALLOC_COSTLY_ORDER) { |
| 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_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 |
| __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)) { |
| page = lru_to_page(&page_list); |
| VM_BUG_ON(PageLRU(page)); |
| SetPageLRU(page); |
| list_del(&page->lru); |
| if (PageActive(page)) |
| add_page_to_active_list(zone, page); |
| else |
| add_page_to_inactive_list(zone, page); |
| 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; |
| } |
| |
| static inline int zone_is_near_oom(struct zone *zone) |
| { |
| return zone->pages_scanned >= (zone_page_state(zone, NR_ACTIVE) |
| + zone_page_state(zone, NR_INACTIVE))*3; |
| } |
| |
| /* |
| * 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) |
| { |
| unsigned long pgmoved; |
| int pgdeactivate = 0; |
| unsigned long pgscanned; |
| LIST_HEAD(l_hold); /* The pages which were snipped off */ |
| LIST_HEAD(l_inactive); /* Pages to go onto the inactive_list */ |
| LIST_HEAD(l_active); /* Pages to go onto the active_list */ |
| struct page *page; |
| struct pagevec pvec; |
| int reclaim_mapped = 0; |
| |
| if (sc->may_swap) { |
| long mapped_ratio; |
| long distress; |
| long swap_tendency; |
| long imbalance; |
| |
| if (zone_is_near_oom(zone)) |
| goto force_reclaim_mapped; |
| |
| /* |
| * `distress' is a measure of how much trouble we're having |
| * reclaiming pages. 0 -> no problems. 100 -> great trouble. |
| */ |
| distress = 100 >> min(zone->prev_priority, priority); |
| |
| /* |
| * The point of this algorithm is to decide when to start |
| * reclaiming mapped memory instead of just pagecache. Work out |
| * how much memory |
| * is mapped. |
| */ |
| mapped_ratio = ((global_page_state(NR_FILE_MAPPED) + |
| global_page_state(NR_ANON_PAGES)) * 100) / |
| vm_total_pages; |
| |
| /* |
| * Now decide how much we really want to unmap some pages. The |
| * mapped ratio is downgraded - just because there's a lot of |
| * mapped memory doesn't necessarily mean that page reclaim |
| * isn't succeeding. |
| * |
| * The distress ratio is important - we don't want to start |
| * going oom. |
| * |
| * A 100% value of vm_swappiness overrides this algorithm |
| * altogether. |
| */ |
| swap_tendency = mapped_ratio / 2 + distress + sc->swappiness; |
| |
| /* |
| * If there's huge imbalance between active and inactive |
| * (think active 100 times larger than inactive) we should |
| * become more permissive, or the system will take too much |
| * cpu before it start swapping during memory pressure. |
| * Distress is about avoiding early-oom, this is about |
| * making swappiness graceful despite setting it to low |
| * values. |
| * |
| * Avoid div by zero with nr_inactive+1, and max resulting |
| * value is vm_total_pages. |
| */ |
| imbalance = zone_page_state(zone, NR_ACTIVE); |
| imbalance /= zone_page_state(zone, NR_INACTIVE) + 1; |
| |
| /* |
| * Reduce the effect of imbalance if swappiness is low, |
| * this means for a swappiness very low, the imbalance |
| * must be much higher than 100 for this logic to make |
| * the difference. |
| * |
| * Max temporary value is vm_total_pages*100. |
| */ |
| imbalance *= (vm_swappiness + 1); |
| imbalance /= 100; |
| |
| /* |
| * If not much of the ram is mapped, makes the imbalance |
| * less relevant, it's high priority we refill the inactive |
| * list with mapped pages only in presence of high ratio of |
| * mapped pages. |
| * |
| * Max temporary value is vm_total_pages*100. |
| */ |
| imbalance *= mapped_ratio; |
| imbalance /= 100; |
| |
| /* apply imbalance feedback to swap_tendency */ |
| swap_tendency += imbalance; |
| |
| /* |
| * Now use this metric to decide whether to start moving mapped |
| * memory onto the inactive list. |
| */ |
| if (swap_tendency >= 100) |
| force_reclaim_mapped: |
| reclaim_mapped = 1; |
| } |
| |
| 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); |
| zone->pages_scanned += pgscanned; |
| __mod_zone_page_state(zone, NR_ACTIVE, -pgmoved); |
| spin_unlock_irq(&zone->lru_lock); |
| |
| while (!list_empty(&l_hold)) { |
| cond_resched(); |
| page = lru_to_page(&l_hold); |
| list_del(&page->lru); |
| if (page_mapped(page)) { |
| if (!reclaim_mapped || |
| (total_swap_pages == 0 && PageAnon(page)) || |
| page_referenced(page, 0, sc->mem_cgroup)) { |
| list_add(&page->lru, &l_active); |
| continue; |
| } |
| } |
| list_add(&page->lru, &l_inactive); |
| } |
| |
| pagevec_init(&pvec, 1); |
| pgmoved = 0; |
| spin_lock_irq(&zone->lru_lock); |
| 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->inactive_list); |
| mem_cgroup_move_lists(page_get_page_cgroup(page), false); |
| pgmoved++; |
| if (!pagevec_add(&pvec, page)) { |
| __mod_zone_page_state(zone, NR_INACTIVE, pgmoved); |
| spin_unlock_irq(&zone->lru_lock); |
| pgdeactivate += pgmoved; |
| pgmoved = 0; |
| if (buffer_heads_over_limit) |
| pagevec_strip(&pvec); |
| __pagevec_release(&pvec); |
| spin_lock_irq(&zone->lru_lock); |
| } |
| } |
| __mod_zone_page_state(zone, NR_INACTIVE, pgmoved); |
| pgdeactivate += pgmoved; |
| if (buffer_heads_over_limit) { |
| spin_unlock_irq(&zone->lru_lock); |
| pagevec_strip(&pvec); |
| spin_lock_irq(&zone->lru_lock); |
| } |
| |
| pgmoved = 0; |
| while (!list_empty(&l_active)) { |
| page = lru_to_page(&l_active); |
| prefetchw_prev_lru_page(page, &l_active, flags); |
| VM_BUG_ON(PageLRU(page)); |
| SetPageLRU(page); |
| VM_BUG_ON(!PageActive(page)); |
| list_move(&page->lru, &zone->active_list); |
| mem_cgroup_move_lists(page_get_page_cgroup(page), true); |
| pgmoved++; |
| if (!pagevec_add(&pvec, page)) { |
| __mod_zone_page_state(zone, NR_ACTIVE, pgmoved); |
| pgmoved = 0; |
| spin_unlock_irq(&zone->lru_lock); |
| __pagevec_release(&pvec); |
| spin_lock_irq(&zone->lru_lock); |
| } |
| } |
| __mod_zone_page_state(zone, NR_ACTIVE, pgmoved); |
| |
| __count_zone_vm_events(PGREFILL, zone, pgscanned); |
| __count_vm_events(PGDEACTIVATE, pgdeactivate); |
| spin_unlock_irq(&zone->lru_lock); |
| |
| pagevec_release(&pvec); |
| } |
| |
| /* |
| * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. |
| */ |
| static unsigned long shrink_zone(int priority, struct zone *zone, |
| struct scan_control *sc) |
| { |
| unsigned long nr_active; |
| unsigned long nr_inactive; |
| unsigned long nr_to_scan; |
| unsigned long nr_reclaimed = 0; |
| |
| /* |
| * Add one to `nr_to_scan' just to make sure that the kernel will |
| * slowly sift through the active list. |
| */ |
| zone->nr_scan_active += |
| (zone_page_state(zone, NR_ACTIVE) >> priority) + 1; |
| nr_active = zone->nr_scan_active; |
| if (nr_active >= sc->swap_cluster_max) |
| zone->nr_scan_active = 0; |
| else |
| nr_active = 0; |
| |
| zone->nr_scan_inactive += |
| (zone_page_state(zone, NR_INACTIVE) >> priority) + 1; |
| nr_inactive = zone->nr_scan_inactive; |
| if (nr_inactive >= sc->swap_cluster_max) |
| zone->nr_scan_inactive = 0; |
| else |
| nr_inactive = 0; |
| |
| while (nr_active || nr_inactive) { |
| if (nr_active) { |
| nr_to_scan = min(nr_active, |
| (unsigned long)sc->swap_cluster_max); |
| nr_active -= nr_to_scan; |
| shrink_active_list(nr_to_scan, zone, sc, priority); |
| } |
| |
| if (nr_inactive) { |
| nr_to_scan = min(nr_inactive, |
| (unsigned long)sc->swap_cluster_max); |
| nr_inactive -= nr_to_scan; |
| nr_reclaimed += shrink_inactive_list(nr_to_scan, zone, |
| sc); |
| } |
| } |
| |
| throttle_vm_writeout(sc->gfp_mask); |
| return nr_reclaimed; |
| } |
| |
| /* |
| * 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 pages_high. Because: |
| * a) The caller may be trying to free *extra* pages to satisfy a higher-order |
| * allocation or |
| * b) The zones may be over pages_high but they must go *over* pages_high to |
| * satisfy the `incremental min' zone defense algorithm. |
| * |
| * Returns the number of reclaimed pages. |
| * |
| * If a zone is deemed to be full of pinned pages then just give it a light |
| * scan then give up on it. |
| */ |
| static unsigned long shrink_zones(int priority, struct zone **zones, |
| struct scan_control *sc) |
| { |
| unsigned long nr_reclaimed = 0; |
| int i; |
| |
| sc->all_unreclaimable = 1; |
| for (i = 0; zones[i] != NULL; i++) { |
| struct zone *zone = zones[i]; |
| |
| if (!populated_zone(zone)) |
| continue; |
| |
| 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; |
| |
| nr_reclaimed += shrink_zone(priority, zone, sc); |
| } |
| return nr_reclaimed; |
| } |
| |
| /* |
| * 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. |
| */ |
| static unsigned long do_try_to_free_pages(struct zone **zones, gfp_t gfp_mask, |
| struct scan_control *sc) |
| { |
| int priority; |
| int ret = 0; |
| unsigned long total_scanned = 0; |
| unsigned long nr_reclaimed = 0; |
| struct reclaim_state *reclaim_state = current->reclaim_state; |
| unsigned long lru_pages = 0; |
| int i; |
| |
| count_vm_event(ALLOCSTALL); |
| |
| for (i = 0; zones[i] != NULL; i++) { |
| struct zone *zone = zones[i]; |
| |
| if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
| continue; |
| |
| lru_pages += zone_page_state(zone, NR_ACTIVE) |
| + zone_page_state(zone, NR_INACTIVE); |
| } |
| |
| for (priority = DEF_PRIORITY; priority >= 0; priority--) { |
| sc->nr_scanned = 0; |
| sc->nr_io_pages = 0; |
| if (!priority) |
| disable_swap_token(); |
| nr_reclaimed += shrink_zones(priority, zones, sc); |
| /* |
| * Don't shrink slabs when reclaiming memory from |
| * over limit cgroups |
| */ |
| if (sc->mem_cgroup == NULL) |
| shrink_slab(sc->nr_scanned, gfp_mask, lru_pages); |
| if (reclaim_state) { |
| nr_reclaimed += reclaim_state->reclaimed_slab; |
| reclaim_state->reclaimed_slab = 0; |
| } |
| total_scanned += sc->nr_scanned; |
| if (nr_reclaimed >= sc->swap_cluster_max) { |
| ret = 1; |
| 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 && |
| sc->nr_io_pages > sc->swap_cluster_max) |
| congestion_wait(WRITE, HZ/10); |
| } |
| /* top priority shrink_caches still had more to do? don't OOM, then */ |
| if (!sc->all_unreclaimable && sc->mem_cgroup == NULL) |
| ret = 1; |
| 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; |
| for (i = 0; zones[i] != NULL; i++) { |
| struct zone *zone = zones[i]; |
| |
| if (!cpuset_zone_allowed_hardwall(zone, GFP_KERNEL)) |
| continue; |
| |
| zone->prev_priority = priority; |
| } |
| return ret; |
| } |
| |
| unsigned long try_to_free_pages(struct zone **zones, int order, gfp_t gfp_mask) |
| { |
| struct scan_control sc = { |
| .gfp_mask = gfp_mask, |
| .may_writepage = !laptop_mode, |
| .swap_cluster_max = SWAP_CLUSTER_MAX, |
| .may_swap = 1, |
| .swappiness = vm_swappiness, |
| .order = order, |
| .mem_cgroup = NULL, |
| .isolate_pages = isolate_pages_global, |
| }; |
| |
| return do_try_to_free_pages(zones, gfp_mask, &sc); |
| } |
| |
| #ifdef CONFIG_CGROUP_MEM_CONT |
| |
| unsigned long try_to_free_mem_cgroup_pages(struct mem_cgroup *mem_cont, |
| gfp_t gfp_mask) |
| { |
| struct scan_control sc = { |
| .gfp_mask = gfp_mask, |
| .may_writepage = !laptop_mode, |
| .may_swap = 1, |
| .swap_cluster_max = SWAP_CLUSTER_MAX, |
| .swappiness = vm_swappiness, |
| .order = 0, |
| .mem_cgroup = mem_cont, |
| .isolate_pages = mem_cgroup_isolate_pages, |
| }; |
| int node; |
| struct zone **zones; |
| int target_zone = gfp_zone(GFP_HIGHUSER_MOVABLE); |
| |
| for_each_online_node(node) { |
| zones = NODE_DATA(node)->node_zonelists[target_zone].zones; |
| if (do_try_to_free_pages(zones, sc.gfp_mask, &sc)) |
| return 1; |
| } |
| return 0; |
| } |
| #endif |
| |
| /* |
| * For kswapd, balance_pgdat() will work across all this node's zones until |
| * they are all at pages_high. |
| * |
| * 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 > pages_high, but once a zone is found to have |
| * free_pages <= pages_high, 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; |
| unsigned long nr_reclaimed; |
| struct reclaim_state *reclaim_state = current->reclaim_state; |
| struct scan_control sc = { |
| .gfp_mask = GFP_KERNEL, |
| .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 == pages_high. |
| */ |
| int temp_priority[MAX_NR_ZONES]; |
| |
| loop_again: |
| total_scanned = 0; |
| 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(); |
| |
| sc.nr_io_pages = 0; |
| 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; |
| |
| if (!zone_watermark_ok(zone, order, zone->pages_high, |
| 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_page_state(zone, NR_ACTIVE) |
| + zone_page_state(zone, NR_INACTIVE); |
| } |
| |
| /* |
| * 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, zone->pages_high, |
| 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*zone->pages_high, |
| end_zone, 0)) |
| nr_reclaimed += shrink_zone(priority, zone, &sc); |
| reclaim_state->reclaimed_slab = 0; |
| nr_slab = shrink_slab(sc.nr_scanned, GFP_KERNEL, |
| lru_pages); |
| 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_page_state(zone, NR_ACTIVE) |
| + zone_page_state(zone, NR_INACTIVE)) * 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 > nr_reclaimed + 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 && |
| sc.nr_io_pages > sc.swap_cluster_max) |
| 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 (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(); |
| |
| goto loop_again; |
| } |
| |
| return 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, |
| }; |
| cpumask_t cpumask; |
| |
| cpumask = node_to_cpumask(pgdat->node_id); |
| if (!cpus_empty(cpumask)) |
| set_cpus_allowed(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, zone->pages_low, 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); |
| } |
| |
| #ifdef CONFIG_PM |
| /* |
| * Helper function for shrink_all_memory(). Tries to reclaim 'nr_pages' pages |
| * from LRU lists system-wide, for given pass and priority, and returns the |
| * number of reclaimed pages |
| * |
| * For pass > 3 we also try to shrink the LRU lists that contain a few pages |
| */ |
| static unsigned long shrink_all_zones(unsigned long nr_pages, int prio, |
| int pass, struct scan_control *sc) |
| { |
| struct zone *zone; |
| unsigned long nr_to_scan, ret = 0; |
| |
| for_each_zone(zone) { |
| |
| if (!populated_zone(zone)) |
| continue; |
| |
| if (zone_is_all_unreclaimable(zone) && prio != DEF_PRIORITY) |
| continue; |
| |
| /* For pass = 0 we don't shrink the active list */ |
| if (pass > 0) { |
| zone->nr_scan_active += |
| (zone_page_state(zone, NR_ACTIVE) >> prio) + 1; |
| if (zone->nr_scan_active >= nr_pages || pass > 3) { |
| zone->nr_scan_active = 0; |
| nr_to_scan = min(nr_pages, |
| zone_page_state(zone, NR_ACTIVE)); |
| shrink_active_list(nr_to_scan, zone, sc, prio); |
| } |
| } |
| |
| zone->nr_scan_inactive += |
| (zone_page_state(zone, NR_INACTIVE) >> prio) + 1; |
| if (zone->nr_scan_inactive >= nr_pages || pass > 3) { |
| zone->nr_scan_inactive = 0; |
| nr_to_scan = min(nr_pages, |
| zone_page_state(zone, NR_INACTIVE)); |
| ret += shrink_inactive_list(nr_to_scan, zone, sc); |
| if (ret >= nr_pages) |
| return ret; |
| } |
| } |
| |
| return ret; |
| } |
| |
| static unsigned long count_lru_pages(void) |
| { |
| return global_page_state(NR_ACTIVE) + global_page_state(NR_INACTIVE); |
| } |
| |
| /* |
| * 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; |
| unsigned long ret = 0; |
| int pass; |
| struct reclaim_state reclaim_state; |
| struct scan_control sc = { |
| .gfp_mask = GFP_KERNEL, |
| .may_swap = 0, |
| .swap_cluster_max = nr_pages, |
| .may_writepage = 1, |
| .swappiness = vm_swappiness, |
| .isolate_pages = isolate_pages_global, |
| }; |
| |
| current->reclaim_state = &reclaim_state; |
| |
| lru_pages = count_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; |
| |
| ret += reclaim_state.reclaimed_slab; |
| if (ret >= 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_swap = 1; |
| sc.swappiness = 100; |
| } |
| |
| for (prio = DEF_PRIORITY; prio >= 0; prio--) { |
| unsigned long nr_to_scan = nr_pages - ret; |
| |
| sc.nr_scanned = 0; |
| ret += shrink_all_zones(nr_to_scan, prio, pass, &sc); |
| if (ret >= nr_pages) |
| goto out; |
| |
| reclaim_state.reclaimed_slab = 0; |
| shrink_slab(sc.nr_scanned, sc.gfp_mask, |
| count_lru_pages()); |
| ret += reclaim_state.reclaimed_slab; |
| if (ret >= nr_pages) |
| goto out; |
| |
| if (sc.nr_scanned && prio < DEF_PRIORITY - 2) |
| congestion_wait(WRITE, HZ / 10); |
| } |
| } |
| |
| /* |
| * If ret = 0, we could not shrink LRUs, but there may be something |
| * in slab caches |
| */ |
| if (!ret) { |
| do { |
| reclaim_state.reclaimed_slab = 0; |
| shrink_slab(nr_pages, sc.gfp_mask, count_lru_pages()); |
| ret += reclaim_state.reclaimed_slab; |
| } while (ret < nr_pages && reclaim_state.reclaimed_slab > 0); |
| } |
| |
| out: |
| current->reclaim_state = NULL; |
| |
| return ret; |
| } |
| #endif |
| |
| /* 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) |
| { |
| pg_data_t *pgdat; |
| cpumask_t mask; |
| int nid; |
| |
| if (action == CPU_ONLINE || action == CPU_ONLINE_FROZEN) { |
| for_each_node_state(nid, N_HIGH_MEMORY) { |
| pgdat = NODE_DATA(nid); |
| mask = node_to_cpumask(pgdat->node_id); |
| if (any_online_cpu(mask) != NR_CPUS) |
| /* One of our CPUs online: restore mask */ |
| set_cpus_allowed(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_cache 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; |
| unsigned long nr_reclaimed = 0; |
| struct scan_control sc = { |
| .may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE), |
| .may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP), |
| .swap_cluster_max = max_t(unsigned long, nr_pages, |
| SWAP_CLUSTER_MAX), |
| .gfp_mask = gfp_mask, |
| .swappiness = vm_swappiness, |
| .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); |
| nr_reclaimed += shrink_zone(priority, zone, &sc); |
| priority--; |
| } while (priority >= 0 && 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. |
| */ |
| nr_reclaimed += slab_reclaimable - |
| zone_page_state(zone, NR_SLAB_RECLAIMABLE); |
| } |
| |
| p->reclaim_state = NULL; |
| current->flags &= ~(PF_MEMALLOC | PF_SWAPWRITE); |
| return 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 |