| /* |
| * 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/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 <asm/tlbflush.h> |
| #include <asm/div64.h> |
| |
| #include <linux/swapops.h> |
| |
| /* 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; |
| |
| struct scan_control { |
| /* Ask refill_inactive_zone, or shrink_cache to scan this many pages */ |
| unsigned long nr_to_scan; |
| |
| /* Incremented by the number of inactive pages that were scanned */ |
| unsigned long nr_scanned; |
| |
| /* Incremented by the number of pages reclaimed */ |
| unsigned long nr_reclaimed; |
| |
| unsigned long nr_mapped; /* From page_state */ |
| |
| /* Ask shrink_caches, or shrink_zone to scan at this priority */ |
| unsigned int priority; |
| |
| /* 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; |
| }; |
| |
| /* |
| * The list of shrinker callbacks used by to apply pressure to |
| * ageable caches. |
| */ |
| struct shrinker { |
| shrinker_t shrinker; |
| struct list_head list; |
| int seeks; /* seeks to recreate an obj */ |
| long nr; /* objs pending delete */ |
| }; |
| |
| #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; |
| static long total_memory; |
| |
| static LIST_HEAD(shrinker_list); |
| static DECLARE_RWSEM(shrinker_rwsem); |
| |
| /* |
| * Add a shrinker callback to be called from the vm |
| */ |
| struct shrinker *set_shrinker(int seeks, shrinker_t theshrinker) |
| { |
| struct shrinker *shrinker; |
| |
| shrinker = kmalloc(sizeof(*shrinker), GFP_KERNEL); |
| if (shrinker) { |
| shrinker->shrinker = theshrinker; |
| shrinker->seeks = seeks; |
| shrinker->nr = 0; |
| down_write(&shrinker_rwsem); |
| list_add_tail(&shrinker->list, &shrinker_list); |
| up_write(&shrinker_rwsem); |
| } |
| return shrinker; |
| } |
| EXPORT_SYMBOL(set_shrinker); |
| |
| /* |
| * Remove one |
| */ |
| void remove_shrinker(struct shrinker *shrinker) |
| { |
| down_write(&shrinker_rwsem); |
| list_del(&shrinker->list); |
| up_write(&shrinker_rwsem); |
| kfree(shrinker); |
| } |
| EXPORT_SYMBOL(remove_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 encounted 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. |
| */ |
| int shrink_slab(unsigned long scanned, gfp_t gfp_mask, unsigned long lru_pages) |
| { |
| struct shrinker *shrinker; |
| int 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->shrinker)(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->shrinker)(0, gfp_mask); |
| shrink_ret = (*shrinker->shrinker)(this_scan, gfp_mask); |
| if (shrink_ret == -1) |
| break; |
| if (shrink_ret < nr_before) |
| ret += nr_before - shrink_ret; |
| mod_page_state(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) { |
| if (error == -ENOSPC) |
| set_bit(AS_ENOSPC, &mapping->flags); |
| else |
| set_bit(AS_EIO, &mapping->flags); |
| } |
| unlock_page(page); |
| } |
| |
| /* |
| * pageout is called by shrink_list() for each dirty page. Calls ->writepage(). |
| */ |
| static pageout_t pageout(struct page *page, struct address_space *mapping) |
| { |
| /* |
| * 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, |
| .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; |
| } |
| if (!PageWriteback(page)) { |
| /* synchronous write or broken a_ops? */ |
| ClearPageReclaim(page); |
| } |
| |
| return PAGE_SUCCESS; |
| } |
| |
| return PAGE_CLEAN; |
| } |
| |
| static int remove_mapping(struct address_space *mapping, struct page *page) |
| { |
| if (!mapping) |
| return 0; /* truncate got there first */ |
| |
| write_lock_irq(&mapping->tree_lock); |
| |
| /* |
| * The non-racy check for busy page. It is critical to check |
| * PageDirty _after_ making sure that the page is freeable and |
| * not in use by anybody. (pagecache + us == 2) |
| */ |
| 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_list adds the number of reclaimed pages to sc->nr_reclaimed |
| */ |
| static int shrink_list(struct list_head *page_list, struct scan_control *sc) |
| { |
| LIST_HEAD(ret_pages); |
| struct pagevec freed_pvec; |
| int pgactivate = 0; |
| int 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; |
| |
| 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++; |
| |
| if (PageWriteback(page)) |
| goto keep_locked; |
| |
| referenced = page_referenced(page, 1); |
| /* In active use or really unfreeable? Activate it. */ |
| if (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 (!sc->may_swap) |
| goto keep_locked; |
| if (!add_to_swap(page, GFP_ATOMIC)) |
| goto activate_locked; |
| } |
| #endif /* CONFIG_SWAP */ |
| |
| mapping = page_mapping(page); |
| may_enter_fs = (sc->gfp_mask & __GFP_FS) || |
| (PageSwapCache(page) && (sc->gfp_mask & __GFP_IO)); |
| |
| /* |
| * The page is mapped into the page tables of one or more |
| * processes. Try to unmap it here. |
| */ |
| if (page_mapped(page) && mapping) { |
| /* |
| * No unmapping if we do not swap |
| */ |
| if (!sc->may_swap) |
| goto keep_locked; |
| |
| 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 (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)) { |
| 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 (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 (!remove_mapping(mapping, page)) |
| goto keep_locked; |
| |
| free_it: |
| unlock_page(page); |
| 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); |
| BUG_ON(PageLRU(page)); |
| } |
| list_splice(&ret_pages, page_list); |
| if (pagevec_count(&freed_pvec)) |
| __pagevec_release_nonlru(&freed_pvec); |
| mod_page_state(pgactivate, pgactivate); |
| sc->nr_reclaimed += reclaimed; |
| return reclaimed; |
| } |
| |
| #ifdef CONFIG_MIGRATION |
| static inline void move_to_lru(struct page *page) |
| { |
| list_del(&page->lru); |
| if (PageActive(page)) { |
| /* |
| * lru_cache_add_active checks that |
| * the PG_active bit is off. |
| */ |
| ClearPageActive(page); |
| lru_cache_add_active(page); |
| } else { |
| lru_cache_add(page); |
| } |
| put_page(page); |
| } |
| |
| /* |
| * Add isolated pages on the list back to the LRU. |
| * |
| * returns the number of pages put back. |
| */ |
| int putback_lru_pages(struct list_head *l) |
| { |
| struct page *page; |
| struct page *page2; |
| int count = 0; |
| |
| list_for_each_entry_safe(page, page2, l, lru) { |
| move_to_lru(page); |
| count++; |
| } |
| return count; |
| } |
| |
| /* |
| * Non migratable page |
| */ |
| int fail_migrate_page(struct page *newpage, struct page *page) |
| { |
| return -EIO; |
| } |
| EXPORT_SYMBOL(fail_migrate_page); |
| |
| /* |
| * swapout a single page |
| * page is locked upon entry, unlocked on exit |
| */ |
| static int swap_page(struct page *page) |
| { |
| struct address_space *mapping = page_mapping(page); |
| |
| if (page_mapped(page) && mapping) |
| if (try_to_unmap(page, 1) != SWAP_SUCCESS) |
| goto unlock_retry; |
| |
| if (PageDirty(page)) { |
| /* Page is dirty, try to write it out here */ |
| switch(pageout(page, mapping)) { |
| case PAGE_KEEP: |
| case PAGE_ACTIVATE: |
| goto unlock_retry; |
| |
| case PAGE_SUCCESS: |
| goto retry; |
| |
| case PAGE_CLEAN: |
| ; /* try to free the page below */ |
| } |
| } |
| |
| if (PagePrivate(page)) { |
| if (!try_to_release_page(page, GFP_KERNEL) || |
| (!mapping && page_count(page) == 1)) |
| goto unlock_retry; |
| } |
| |
| if (remove_mapping(mapping, page)) { |
| /* Success */ |
| unlock_page(page); |
| return 0; |
| } |
| |
| unlock_retry: |
| unlock_page(page); |
| |
| retry: |
| return -EAGAIN; |
| } |
| EXPORT_SYMBOL(swap_page); |
| |
| /* |
| * Page migration was first developed in the context of the memory hotplug |
| * project. The main authors of the migration code are: |
| * |
| * IWAMOTO Toshihiro <iwamoto@valinux.co.jp> |
| * Hirokazu Takahashi <taka@valinux.co.jp> |
| * Dave Hansen <haveblue@us.ibm.com> |
| * Christoph Lameter <clameter@sgi.com> |
| */ |
| |
| /* |
| * Remove references for a page and establish the new page with the correct |
| * basic settings to be able to stop accesses to the page. |
| */ |
| int migrate_page_remove_references(struct page *newpage, |
| struct page *page, int nr_refs) |
| { |
| struct address_space *mapping = page_mapping(page); |
| struct page **radix_pointer; |
| |
| /* |
| * Avoid doing any of the following work if the page count |
| * indicates that the page is in use or truncate has removed |
| * the page. |
| */ |
| if (!mapping || page_mapcount(page) + nr_refs != page_count(page)) |
| return 1; |
| |
| /* |
| * Establish swap ptes for anonymous pages or destroy pte |
| * maps for files. |
| * |
| * In order to reestablish file backed mappings the fault handlers |
| * will take the radix tree_lock which may then be used to stop |
| * processses from accessing this page until the new page is ready. |
| * |
| * A process accessing via a swap pte (an anonymous page) will take a |
| * page_lock on the old page which will block the process until the |
| * migration attempt is complete. At that time the PageSwapCache bit |
| * will be examined. If the page was migrated then the PageSwapCache |
| * bit will be clear and the operation to retrieve the page will be |
| * retried which will find the new page in the radix tree. Then a new |
| * direct mapping may be generated based on the radix tree contents. |
| * |
| * If the page was not migrated then the PageSwapCache bit |
| * is still set and the operation may continue. |
| */ |
| try_to_unmap(page, 1); |
| |
| /* |
| * Give up if we were unable to remove all mappings. |
| */ |
| if (page_mapcount(page)) |
| return 1; |
| |
| write_lock_irq(&mapping->tree_lock); |
| |
| radix_pointer = (struct page **)radix_tree_lookup_slot( |
| &mapping->page_tree, |
| page_index(page)); |
| |
| if (!page_mapping(page) || page_count(page) != nr_refs || |
| *radix_pointer != page) { |
| write_unlock_irq(&mapping->tree_lock); |
| return 1; |
| } |
| |
| /* |
| * Now we know that no one else is looking at the page. |
| * |
| * Certain minimal information about a page must be available |
| * in order for other subsystems to properly handle the page if they |
| * find it through the radix tree update before we are finished |
| * copying the page. |
| */ |
| get_page(newpage); |
| newpage->index = page->index; |
| newpage->mapping = page->mapping; |
| if (PageSwapCache(page)) { |
| SetPageSwapCache(newpage); |
| set_page_private(newpage, page_private(page)); |
| } |
| |
| *radix_pointer = newpage; |
| __put_page(page); |
| write_unlock_irq(&mapping->tree_lock); |
| |
| return 0; |
| } |
| EXPORT_SYMBOL(migrate_page_remove_references); |
| |
| /* |
| * Copy the page to its new location |
| */ |
| void migrate_page_copy(struct page *newpage, struct page *page) |
| { |
| copy_highpage(newpage, page); |
| |
| if (PageError(page)) |
| SetPageError(newpage); |
| if (PageReferenced(page)) |
| SetPageReferenced(newpage); |
| if (PageUptodate(page)) |
| SetPageUptodate(newpage); |
| if (PageActive(page)) |
| SetPageActive(newpage); |
| if (PageChecked(page)) |
| SetPageChecked(newpage); |
| if (PageMappedToDisk(page)) |
| SetPageMappedToDisk(newpage); |
| |
| if (PageDirty(page)) { |
| clear_page_dirty_for_io(page); |
| set_page_dirty(newpage); |
| } |
| |
| ClearPageSwapCache(page); |
| ClearPageActive(page); |
| ClearPagePrivate(page); |
| set_page_private(page, 0); |
| page->mapping = NULL; |
| |
| /* |
| * If any waiters have accumulated on the new page then |
| * wake them up. |
| */ |
| if (PageWriteback(newpage)) |
| end_page_writeback(newpage); |
| } |
| EXPORT_SYMBOL(migrate_page_copy); |
| |
| /* |
| * Common logic to directly migrate a single page suitable for |
| * pages that do not use PagePrivate. |
| * |
| * Pages are locked upon entry and exit. |
| */ |
| int migrate_page(struct page *newpage, struct page *page) |
| { |
| BUG_ON(PageWriteback(page)); /* Writeback must be complete */ |
| |
| if (migrate_page_remove_references(newpage, page, 2)) |
| return -EAGAIN; |
| |
| migrate_page_copy(newpage, page); |
| |
| /* |
| * Remove auxiliary swap entries and replace |
| * them with real ptes. |
| * |
| * Note that a real pte entry will allow processes that are not |
| * waiting on the page lock to use the new page via the page tables |
| * before the new page is unlocked. |
| */ |
| remove_from_swap(newpage); |
| return 0; |
| } |
| EXPORT_SYMBOL(migrate_page); |
| |
| /* |
| * migrate_pages |
| * |
| * Two lists are passed to this function. The first list |
| * contains the pages isolated from the LRU to be migrated. |
| * The second list contains new pages that the pages isolated |
| * can be moved to. If the second list is NULL then all |
| * pages are swapped out. |
| * |
| * The function returns after 10 attempts or if no pages |
| * are movable anymore because to has become empty |
| * or no retryable pages exist anymore. |
| * |
| * Return: Number of pages not migrated when "to" ran empty. |
| */ |
| int migrate_pages(struct list_head *from, struct list_head *to, |
| struct list_head *moved, struct list_head *failed) |
| { |
| int retry; |
| int nr_failed = 0; |
| int pass = 0; |
| struct page *page; |
| struct page *page2; |
| int swapwrite = current->flags & PF_SWAPWRITE; |
| int rc; |
| |
| if (!swapwrite) |
| current->flags |= PF_SWAPWRITE; |
| |
| redo: |
| retry = 0; |
| |
| list_for_each_entry_safe(page, page2, from, lru) { |
| struct page *newpage = NULL; |
| struct address_space *mapping; |
| |
| cond_resched(); |
| |
| rc = 0; |
| if (page_count(page) == 1) |
| /* page was freed from under us. So we are done. */ |
| goto next; |
| |
| if (to && list_empty(to)) |
| break; |
| |
| /* |
| * Skip locked pages during the first two passes to give the |
| * functions holding the lock time to release the page. Later we |
| * use lock_page() to have a higher chance of acquiring the |
| * lock. |
| */ |
| rc = -EAGAIN; |
| if (pass > 2) |
| lock_page(page); |
| else |
| if (TestSetPageLocked(page)) |
| goto next; |
| |
| /* |
| * Only wait on writeback if we have already done a pass where |
| * we we may have triggered writeouts for lots of pages. |
| */ |
| if (pass > 0) { |
| wait_on_page_writeback(page); |
| } else { |
| if (PageWriteback(page)) |
| goto unlock_page; |
| } |
| |
| /* |
| * Anonymous pages must have swap cache references otherwise |
| * the information contained in the page maps cannot be |
| * preserved. |
| */ |
| if (PageAnon(page) && !PageSwapCache(page)) { |
| if (!add_to_swap(page, GFP_KERNEL)) { |
| rc = -ENOMEM; |
| goto unlock_page; |
| } |
| } |
| |
| if (!to) { |
| rc = swap_page(page); |
| goto next; |
| } |
| |
| newpage = lru_to_page(to); |
| lock_page(newpage); |
| |
| /* |
| * Pages are properly locked and writeback is complete. |
| * Try to migrate the page. |
| */ |
| mapping = page_mapping(page); |
| if (!mapping) |
| goto unlock_both; |
| |
| if (mapping->a_ops->migratepage) { |
| /* |
| * Most pages have a mapping and most filesystems |
| * should provide a migration function. Anonymous |
| * pages are part of swap space which also has its |
| * own migration function. This is the most common |
| * path for page migration. |
| */ |
| rc = mapping->a_ops->migratepage(newpage, page); |
| goto unlock_both; |
| } |
| |
| /* |
| * Default handling if a filesystem does not provide |
| * a migration function. We can only migrate clean |
| * pages so try to write out any dirty pages first. |
| */ |
| if (PageDirty(page)) { |
| switch (pageout(page, mapping)) { |
| case PAGE_KEEP: |
| case PAGE_ACTIVATE: |
| goto unlock_both; |
| |
| case PAGE_SUCCESS: |
| unlock_page(newpage); |
| goto next; |
| |
| case PAGE_CLEAN: |
| ; /* try to migrate the page below */ |
| } |
| } |
| |
| /* |
| * Buffers are managed in a filesystem specific way. |
| * We must have no buffers or drop them. |
| */ |
| if (!page_has_buffers(page) || |
| try_to_release_page(page, GFP_KERNEL)) { |
| rc = migrate_page(newpage, page); |
| goto unlock_both; |
| } |
| |
| /* |
| * On early passes with mapped pages simply |
| * retry. There may be a lock held for some |
| * buffers that may go away. Later |
| * swap them out. |
| */ |
| if (pass > 4) { |
| /* |
| * Persistently unable to drop buffers..... As a |
| * measure of last resort we fall back to |
| * swap_page(). |
| */ |
| unlock_page(newpage); |
| newpage = NULL; |
| rc = swap_page(page); |
| goto next; |
| } |
| |
| unlock_both: |
| unlock_page(newpage); |
| |
| unlock_page: |
| unlock_page(page); |
| |
| next: |
| if (rc == -EAGAIN) { |
| retry++; |
| } else if (rc) { |
| /* Permanent failure */ |
| list_move(&page->lru, failed); |
| nr_failed++; |
| } else { |
| if (newpage) { |
| /* Successful migration. Return page to LRU */ |
| move_to_lru(newpage); |
| } |
| list_move(&page->lru, moved); |
| } |
| } |
| if (retry && pass++ < 10) |
| goto redo; |
| |
| if (!swapwrite) |
| current->flags &= ~PF_SWAPWRITE; |
| |
| return nr_failed + retry; |
| } |
| |
| /* |
| * Isolate one page from the LRU lists and put it on the |
| * indicated list with elevated refcount. |
| * |
| * Result: |
| * 0 = page not on LRU list |
| * 1 = page removed from LRU list and added to the specified list. |
| */ |
| int isolate_lru_page(struct page *page) |
| { |
| int ret = 0; |
| |
| if (PageLRU(page)) { |
| struct zone *zone = page_zone(page); |
| spin_lock_irq(&zone->lru_lock); |
| if (TestClearPageLRU(page)) { |
| ret = 1; |
| get_page(page); |
| if (PageActive(page)) |
| del_page_from_active_list(zone, page); |
| else |
| del_page_from_inactive_list(zone, page); |
| } |
| spin_unlock_irq(&zone->lru_lock); |
| } |
| |
| return ret; |
| } |
| #endif |
| |
| /* |
| * 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. |
| * |
| * returns how many pages were moved onto *@dst. |
| */ |
| static int isolate_lru_pages(int nr_to_scan, struct list_head *src, |
| struct list_head *dst, int *scanned) |
| { |
| int nr_taken = 0; |
| struct page *page; |
| int scan = 0; |
| |
| while (scan++ < nr_to_scan && !list_empty(src)) { |
| page = lru_to_page(src); |
| prefetchw_prev_lru_page(page, src, flags); |
| |
| if (!TestClearPageLRU(page)) |
| BUG(); |
| list_del(&page->lru); |
| if (get_page_testone(page)) { |
| /* |
| * It is being freed elsewhere |
| */ |
| __put_page(page); |
| SetPageLRU(page); |
| list_add(&page->lru, src); |
| continue; |
| } else { |
| list_add(&page->lru, dst); |
| nr_taken++; |
| } |
| } |
| |
| *scanned = scan; |
| return nr_taken; |
| } |
| |
| /* |
| * shrink_cache() adds the number of pages reclaimed to sc->nr_reclaimed |
| */ |
| static void shrink_cache(struct zone *zone, struct scan_control *sc) |
| { |
| LIST_HEAD(page_list); |
| struct pagevec pvec; |
| int max_scan = sc->nr_to_scan; |
| |
| pagevec_init(&pvec, 1); |
| |
| lru_add_drain(); |
| spin_lock_irq(&zone->lru_lock); |
| while (max_scan > 0) { |
| struct page *page; |
| int nr_taken; |
| int nr_scan; |
| int nr_freed; |
| |
| nr_taken = isolate_lru_pages(sc->swap_cluster_max, |
| &zone->inactive_list, |
| &page_list, &nr_scan); |
| zone->nr_inactive -= nr_taken; |
| zone->pages_scanned += nr_scan; |
| spin_unlock_irq(&zone->lru_lock); |
| |
| if (nr_taken == 0) |
| goto done; |
| |
| max_scan -= nr_scan; |
| nr_freed = shrink_list(&page_list, sc); |
| |
| local_irq_disable(); |
| if (current_is_kswapd()) { |
| __mod_page_state_zone(zone, pgscan_kswapd, nr_scan); |
| __mod_page_state(kswapd_steal, nr_freed); |
| } else |
| __mod_page_state_zone(zone, pgscan_direct, nr_scan); |
| __mod_page_state_zone(zone, pgsteal, nr_freed); |
| |
| spin_lock(&zone->lru_lock); |
| /* |
| * Put back any unfreeable pages. |
| */ |
| while (!list_empty(&page_list)) { |
| page = lru_to_page(&page_list); |
| if (TestSetPageLRU(page)) |
| BUG(); |
| 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); |
| } |
| } |
| } |
| spin_unlock_irq(&zone->lru_lock); |
| done: |
| pagevec_release(&pvec); |
| } |
| |
| /* |
| * 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 |
| refill_inactive_zone(struct zone *zone, struct scan_control *sc) |
| { |
| int pgmoved; |
| int pgdeactivate = 0; |
| int pgscanned; |
| int nr_pages = sc->nr_to_scan; |
| 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 (unlikely(sc->may_swap)) { |
| long mapped_ratio; |
| long distress; |
| long swap_tendency; |
| |
| /* |
| * `distress' is a measure of how much trouble we're having |
| * reclaiming pages. 0 -> no problems. 100 -> great trouble. |
| */ |
| distress = 100 >> zone->prev_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 = (sc->nr_mapped * 100) / total_memory; |
| |
| /* |
| * 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 + vm_swappiness; |
| |
| /* |
| * Now use this metric to decide whether to start moving mapped |
| * memory onto the inactive list. |
| */ |
| if (swap_tendency >= 100) |
| reclaim_mapped = 1; |
| } |
| |
| lru_add_drain(); |
| spin_lock_irq(&zone->lru_lock); |
| pgmoved = isolate_lru_pages(nr_pages, &zone->active_list, |
| &l_hold, &pgscanned); |
| zone->pages_scanned += pgscanned; |
| 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)) { |
| 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); |
| if (TestSetPageLRU(page)) |
| BUG(); |
| if (!TestClearPageActive(page)) |
| BUG(); |
| list_move(&page->lru, &zone->inactive_list); |
| pgmoved++; |
| if (!pagevec_add(&pvec, page)) { |
| 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); |
| } |
| } |
| 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); |
| if (TestSetPageLRU(page)) |
| BUG(); |
| BUG_ON(!PageActive(page)); |
| list_move(&page->lru, &zone->active_list); |
| pgmoved++; |
| if (!pagevec_add(&pvec, page)) { |
| zone->nr_active += pgmoved; |
| pgmoved = 0; |
| spin_unlock_irq(&zone->lru_lock); |
| __pagevec_release(&pvec); |
| spin_lock_irq(&zone->lru_lock); |
| } |
| } |
| zone->nr_active += pgmoved; |
| spin_unlock(&zone->lru_lock); |
| |
| __mod_page_state_zone(zone, pgrefill, pgscanned); |
| __mod_page_state(pgdeactivate, pgdeactivate); |
| local_irq_enable(); |
| |
| pagevec_release(&pvec); |
| } |
| |
| /* |
| * This is a basic per-zone page freer. Used by both kswapd and direct reclaim. |
| */ |
| static void |
| shrink_zone(struct zone *zone, struct scan_control *sc) |
| { |
| unsigned long nr_active; |
| unsigned long nr_inactive; |
| |
| atomic_inc(&zone->reclaim_in_progress); |
| |
| /* |
| * 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->nr_active >> sc->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->nr_inactive >> sc->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) { |
| sc->nr_to_scan = min(nr_active, |
| (unsigned long)sc->swap_cluster_max); |
| nr_active -= sc->nr_to_scan; |
| refill_inactive_zone(zone, sc); |
| } |
| |
| if (nr_inactive) { |
| sc->nr_to_scan = min(nr_inactive, |
| (unsigned long)sc->swap_cluster_max); |
| nr_inactive -= sc->nr_to_scan; |
| shrink_cache(zone, sc); |
| } |
| } |
| |
| throttle_vm_writeout(); |
| |
| atomic_dec(&zone->reclaim_in_progress); |
| } |
| |
| /* |
| * 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 void |
| shrink_caches(struct zone **zones, struct scan_control *sc) |
| { |
| int i; |
| |
| for (i = 0; zones[i] != NULL; i++) { |
| struct zone *zone = zones[i]; |
| |
| if (!populated_zone(zone)) |
| continue; |
| |
| if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) |
| continue; |
| |
| zone->temp_priority = sc->priority; |
| if (zone->prev_priority > sc->priority) |
| zone->prev_priority = sc->priority; |
| |
| if (zone->all_unreclaimable && sc->priority != DEF_PRIORITY) |
| continue; /* Let kswapd poll it */ |
| |
| shrink_zone(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. |
| */ |
| int try_to_free_pages(struct zone **zones, gfp_t gfp_mask) |
| { |
| int priority; |
| int ret = 0; |
| int total_scanned = 0, total_reclaimed = 0; |
| struct reclaim_state *reclaim_state = current->reclaim_state; |
| struct scan_control sc; |
| unsigned long lru_pages = 0; |
| int i; |
| |
| sc.gfp_mask = gfp_mask; |
| sc.may_writepage = !laptop_mode; |
| sc.may_swap = 1; |
| |
| inc_page_state(allocstall); |
| |
| for (i = 0; zones[i] != NULL; i++) { |
| struct zone *zone = zones[i]; |
| |
| if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) |
| continue; |
| |
| zone->temp_priority = DEF_PRIORITY; |
| lru_pages += zone->nr_active + zone->nr_inactive; |
| } |
| |
| for (priority = DEF_PRIORITY; priority >= 0; priority--) { |
| sc.nr_mapped = read_page_state(nr_mapped); |
| sc.nr_scanned = 0; |
| sc.nr_reclaimed = 0; |
| sc.priority = priority; |
| sc.swap_cluster_max = SWAP_CLUSTER_MAX; |
| if (!priority) |
| disable_swap_token(); |
| shrink_caches(zones, &sc); |
| shrink_slab(sc.nr_scanned, gfp_mask, lru_pages); |
| if (reclaim_state) { |
| sc.nr_reclaimed += reclaim_state->reclaimed_slab; |
| reclaim_state->reclaimed_slab = 0; |
| } |
| total_scanned += sc.nr_scanned; |
| total_reclaimed += sc.nr_reclaimed; |
| if (total_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) |
| blk_congestion_wait(WRITE, HZ/10); |
| } |
| out: |
| for (i = 0; zones[i] != 0; i++) { |
| struct zone *zone = zones[i]; |
| |
| if (!cpuset_zone_allowed(zone, __GFP_HARDWALL)) |
| continue; |
| |
| zone->prev_priority = zone->temp_priority; |
| } |
| return ret; |
| } |
| |
| /* |
| * For kswapd, balance_pgdat() will work across all this node's zones until |
| * they are all at pages_high. |
| * |
| * If `nr_pages' is non-zero then it is the number of pages which are to be |
| * reclaimed, regardless of the zone occupancies. This is a software suspend |
| * special. |
| * |
| * 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 int balance_pgdat(pg_data_t *pgdat, int nr_pages, int order) |
| { |
| int to_free = nr_pages; |
| int all_zones_ok; |
| int priority; |
| int i; |
| int total_scanned, total_reclaimed; |
| struct reclaim_state *reclaim_state = current->reclaim_state; |
| struct scan_control sc; |
| |
| loop_again: |
| total_scanned = 0; |
| total_reclaimed = 0; |
| sc.gfp_mask = GFP_KERNEL; |
| sc.may_writepage = !laptop_mode; |
| sc.may_swap = 1; |
| sc.nr_mapped = read_page_state(nr_mapped); |
| |
| inc_page_state(pageoutrun); |
| |
| for (i = 0; i < pgdat->nr_zones; i++) { |
| struct zone *zone = pgdat->node_zones + i; |
| |
| zone->temp_priority = 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; |
| |
| if (nr_pages == 0) { |
| /* |
| * Scan in the highmem->dma direction for the highest |
| * zone which needs scanning |
| */ |
| for (i = pgdat->nr_zones - 1; i >= 0; i--) { |
| struct zone *zone = pgdat->node_zones + i; |
| |
| if (!populated_zone(zone)) |
| continue; |
| |
| if (zone->all_unreclaimable && |
| priority != DEF_PRIORITY) |
| continue; |
| |
| if (!zone_watermark_ok(zone, order, |
| zone->pages_high, 0, 0)) { |
| end_zone = i; |
| goto scan; |
| } |
| } |
| goto out; |
| } else { |
| end_zone = pgdat->nr_zones - 1; |
| } |
| scan: |
| for (i = 0; i <= end_zone; i++) { |
| struct zone *zone = pgdat->node_zones + i; |
| |
| lru_pages += zone->nr_active + 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->all_unreclaimable && priority != DEF_PRIORITY) |
| continue; |
| |
| if (nr_pages == 0) { /* Not software suspend */ |
| if (!zone_watermark_ok(zone, order, |
| zone->pages_high, end_zone, 0)) |
| all_zones_ok = 0; |
| } |
| zone->temp_priority = priority; |
| if (zone->prev_priority > priority) |
| zone->prev_priority = priority; |
| sc.nr_scanned = 0; |
| sc.nr_reclaimed = 0; |
| sc.priority = priority; |
| sc.swap_cluster_max = nr_pages? nr_pages : SWAP_CLUSTER_MAX; |
| shrink_zone(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_reclaimed += sc.nr_reclaimed; |
| total_scanned += sc.nr_scanned; |
| if (zone->all_unreclaimable) |
| continue; |
| if (nr_slab == 0 && zone->pages_scanned >= |
| (zone->nr_active + zone->nr_inactive) * 4) |
| zone->all_unreclaimable = 1; |
| /* |
| * If we've done a decent amount of scanning and |
| * the reclaim ratio is low, start doing writepage |
| * even in laptop mode |
| */ |
| if (total_scanned > SWAP_CLUSTER_MAX * 2 && |
| total_scanned > total_reclaimed+total_reclaimed/2) |
| sc.may_writepage = 1; |
| } |
| if (nr_pages && to_free > total_reclaimed) |
| continue; /* swsusp: need to do more work */ |
| 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) |
| blk_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 ((total_reclaimed >= SWAP_CLUSTER_MAX) && (!nr_pages)) |
| break; |
| } |
| out: |
| for (i = 0; i < pgdat->nr_zones; i++) { |
| struct zone *zone = pgdat->node_zones + i; |
| |
| zone->prev_priority = zone->temp_priority; |
| } |
| if (!all_zones_ok) { |
| cond_resched(); |
| goto loop_again; |
| } |
| |
| return total_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; |
| |
| daemonize("kswapd%d", pgdat->node_id); |
| 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; |
| |
| order = 0; |
| for ( ; ; ) { |
| unsigned long new_order; |
| |
| try_to_freeze(); |
| |
| 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 { |
| schedule(); |
| order = pgdat->kswapd_max_order; |
| } |
| finish_wait(&pgdat->kswapd_wait, &wait); |
| |
| balance_pgdat(pgdat, 0, 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(zone, __GFP_HARDWALL)) |
| return; |
| if (!waitqueue_active(&pgdat->kswapd_wait)) |
| return; |
| wake_up_interruptible(&pgdat->kswapd_wait); |
| } |
| |
| #ifdef CONFIG_PM |
| /* |
| * Try to free `nr_pages' of memory, system-wide. Returns the number of freed |
| * pages. |
| */ |
| int shrink_all_memory(int nr_pages) |
| { |
| pg_data_t *pgdat; |
| int nr_to_free = nr_pages; |
| int ret = 0; |
| struct reclaim_state reclaim_state = { |
| .reclaimed_slab = 0, |
| }; |
| |
| current->reclaim_state = &reclaim_state; |
| for_each_pgdat(pgdat) { |
| int freed; |
| freed = balance_pgdat(pgdat, nr_to_free, 0); |
| ret += freed; |
| nr_to_free -= freed; |
| if (nr_to_free <= 0) |
| break; |
| } |
| current->reclaim_state = NULL; |
| return ret; |
| } |
| #endif |
| |
| #ifdef CONFIG_HOTPLUG_CPU |
| /* 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; |
| |
| if (action == CPU_ONLINE) { |
| for_each_pgdat(pgdat) { |
| 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; |
| } |
| #endif /* CONFIG_HOTPLUG_CPU */ |
| |
| static int __init kswapd_init(void) |
| { |
| pg_data_t *pgdat; |
| swap_setup(); |
| for_each_pgdat(pgdat) |
| pgdat->kswapd |
| = find_task_by_pid(kernel_thread(kswapd, pgdat, CLONE_KERNEL)); |
| total_memory = nr_free_pagecache_pages(); |
| 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. |
| * |
| * In the future we may add flags to the mode. However, the page allocator |
| * should only have to check that zone_reclaim_mode != 0 before calling |
| * zone_reclaim(). |
| */ |
| 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 */ |
| #define RECLAIM_SLAB (1<<3) /* Do a global slab shrink if the zone is out of memory */ |
| |
| /* |
| * Mininum time between zone reclaim scans |
| */ |
| int zone_reclaim_interval __read_mostly = 30*HZ; |
| |
| /* |
| * 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 |
| |
| /* |
| * Try to free up some pages from this zone through reclaim. |
| */ |
| int zone_reclaim(struct zone *zone, gfp_t gfp_mask, unsigned int order) |
| { |
| int nr_pages; |
| struct task_struct *p = current; |
| struct reclaim_state reclaim_state; |
| struct scan_control sc; |
| cpumask_t mask; |
| int node_id; |
| |
| if (time_before(jiffies, |
| zone->last_unsuccessful_zone_reclaim + zone_reclaim_interval)) |
| return 0; |
| |
| if (!(gfp_mask & __GFP_WAIT) || |
| zone->all_unreclaimable || |
| atomic_read(&zone->reclaim_in_progress) > 0) |
| return 0; |
| |
| node_id = zone->zone_pgdat->node_id; |
| mask = node_to_cpumask(node_id); |
| if (!cpus_empty(mask) && node_id != numa_node_id()) |
| return 0; |
| |
| sc.may_writepage = !!(zone_reclaim_mode & RECLAIM_WRITE); |
| sc.may_swap = !!(zone_reclaim_mode & RECLAIM_SWAP); |
| sc.nr_scanned = 0; |
| sc.nr_reclaimed = 0; |
| sc.priority = ZONE_RECLAIM_PRIORITY + 1; |
| sc.nr_mapped = read_page_state(nr_mapped); |
| sc.gfp_mask = gfp_mask; |
| |
| disable_swap_token(); |
| |
| nr_pages = 1 << order; |
| if (nr_pages > SWAP_CLUSTER_MAX) |
| sc.swap_cluster_max = nr_pages; |
| else |
| sc.swap_cluster_max = SWAP_CLUSTER_MAX; |
| |
| cond_resched(); |
| p->flags |= PF_MEMALLOC; |
| reclaim_state.reclaimed_slab = 0; |
| p->reclaim_state = &reclaim_state; |
| |
| /* |
| * Free memory by calling shrink zone with increasing priorities |
| * until we have enough memory freed. |
| */ |
| do { |
| sc.priority--; |
| shrink_zone(zone, &sc); |
| |
| } while (sc.nr_reclaimed < nr_pages && sc.priority > 0); |
| |
| if (sc.nr_reclaimed < nr_pages && (zone_reclaim_mode & RECLAIM_SLAB)) { |
| /* |
| * shrink_slab does not currently allow us to determine |
| * how many pages were freed in the zone. So we just |
| * shake the slab and then go offnode for a single allocation. |
| * |
| * shrink_slab will free memory on all zones and may take |
| * a long time. |
| */ |
| shrink_slab(sc.nr_scanned, gfp_mask, order); |
| sc.nr_reclaimed = 1; /* Avoid getting the off node timeout */ |
| } |
| |
| p->reclaim_state = NULL; |
| current->flags &= ~PF_MEMALLOC; |
| |
| if (sc.nr_reclaimed == 0) |
| zone->last_unsuccessful_zone_reclaim = jiffies; |
| |
| return sc.nr_reclaimed >= nr_pages; |
| } |
| #endif |
| |