diff options
author | Fathi Boudra <fathi.boudra@linaro.org> | 2013-04-28 09:33:08 +0300 |
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committer | Fathi Boudra <fathi.boudra@linaro.org> | 2013-04-28 09:33:08 +0300 |
commit | 3b4bd47f8f4ed3aaf7c81c9b5d2d37ad79fadf4a (patch) | |
tree | b9996006addfd7ae70a39672b76843b49aebc189 /mm/migrate.c |
Imported Upstream version 3.9.0HEADupstream/3.9.0upstreammaster
Diffstat (limited to 'mm/migrate.c')
-rw-r--r-- | mm/migrate.c | 1754 |
1 files changed, 1754 insertions, 0 deletions
diff --git a/mm/migrate.c b/mm/migrate.c new file mode 100644 index 00000000..3bbaf5d2 --- /dev/null +++ b/mm/migrate.c @@ -0,0 +1,1754 @@ +/* + * Memory Migration functionality - linux/mm/migration.c + * + * Copyright (C) 2006 Silicon Graphics, Inc., Christoph Lameter + * + * 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 + */ + +#include <linux/migrate.h> +#include <linux/export.h> +#include <linux/swap.h> +#include <linux/swapops.h> +#include <linux/pagemap.h> +#include <linux/buffer_head.h> +#include <linux/mm_inline.h> +#include <linux/nsproxy.h> +#include <linux/pagevec.h> +#include <linux/ksm.h> +#include <linux/rmap.h> +#include <linux/topology.h> +#include <linux/cpu.h> +#include <linux/cpuset.h> +#include <linux/writeback.h> +#include <linux/mempolicy.h> +#include <linux/vmalloc.h> +#include <linux/security.h> +#include <linux/memcontrol.h> +#include <linux/syscalls.h> +#include <linux/hugetlb.h> +#include <linux/hugetlb_cgroup.h> +#include <linux/gfp.h> +#include <linux/balloon_compaction.h> + +#include <asm/tlbflush.h> + +#define CREATE_TRACE_POINTS +#include <trace/events/migrate.h> + +#include "internal.h" + +/* + * migrate_prep() needs to be called before we start compiling a list of pages + * to be migrated using isolate_lru_page(). If scheduling work on other CPUs is + * undesirable, use migrate_prep_local() + */ +int migrate_prep(void) +{ + /* + * Clear the LRU lists so pages can be isolated. + * Note that pages may be moved off the LRU after we have + * drained them. Those pages will fail to migrate like other + * pages that may be busy. + */ + lru_add_drain_all(); + + return 0; +} + +/* Do the necessary work of migrate_prep but not if it involves other CPUs */ +int migrate_prep_local(void) +{ + lru_add_drain(); + + return 0; +} + +/* + * Add isolated pages on the list back to the LRU under page lock + * to avoid leaking evictable pages back onto unevictable list. + */ +void putback_lru_pages(struct list_head *l) +{ + struct page *page; + struct page *page2; + + list_for_each_entry_safe(page, page2, l, lru) { + list_del(&page->lru); + dec_zone_page_state(page, NR_ISOLATED_ANON + + page_is_file_cache(page)); + putback_lru_page(page); + } +} + +/* + * Put previously isolated pages back onto the appropriate lists + * from where they were once taken off for compaction/migration. + * + * This function shall be used instead of putback_lru_pages(), + * whenever the isolated pageset has been built by isolate_migratepages_range() + */ +void putback_movable_pages(struct list_head *l) +{ + struct page *page; + struct page *page2; + + list_for_each_entry_safe(page, page2, l, lru) { + list_del(&page->lru); + dec_zone_page_state(page, NR_ISOLATED_ANON + + page_is_file_cache(page)); + if (unlikely(balloon_page_movable(page))) + balloon_page_putback(page); + else + putback_lru_page(page); + } +} + +/* + * Restore a potential migration pte to a working pte entry + */ +static int remove_migration_pte(struct page *new, struct vm_area_struct *vma, + unsigned long addr, void *old) +{ + struct mm_struct *mm = vma->vm_mm; + swp_entry_t entry; + pmd_t *pmd; + pte_t *ptep, pte; + spinlock_t *ptl; + + if (unlikely(PageHuge(new))) { + ptep = huge_pte_offset(mm, addr); + if (!ptep) + goto out; + ptl = &mm->page_table_lock; + } else { + pmd = mm_find_pmd(mm, addr); + if (!pmd) + goto out; + if (pmd_trans_huge(*pmd)) + goto out; + + ptep = pte_offset_map(pmd, addr); + + /* + * Peek to check is_swap_pte() before taking ptlock? No, we + * can race mremap's move_ptes(), which skips anon_vma lock. + */ + + ptl = pte_lockptr(mm, pmd); + } + + spin_lock(ptl); + pte = *ptep; + if (!is_swap_pte(pte)) + goto unlock; + + entry = pte_to_swp_entry(pte); + + if (!is_migration_entry(entry) || + migration_entry_to_page(entry) != old) + goto unlock; + + get_page(new); + pte = pte_mkold(mk_pte(new, vma->vm_page_prot)); + if (is_write_migration_entry(entry)) + pte = pte_mkwrite(pte); +#ifdef CONFIG_HUGETLB_PAGE + if (PageHuge(new)) { + pte = pte_mkhuge(pte); + pte = arch_make_huge_pte(pte, vma, new, 0); + } +#endif + flush_cache_page(vma, addr, pte_pfn(pte)); + set_pte_at(mm, addr, ptep, pte); + + if (PageHuge(new)) { + if (PageAnon(new)) + hugepage_add_anon_rmap(new, vma, addr); + else + page_dup_rmap(new); + } else if (PageAnon(new)) + page_add_anon_rmap(new, vma, addr); + else + page_add_file_rmap(new); + + /* No need to invalidate - it was non-present before */ + update_mmu_cache(vma, addr, ptep); +unlock: + pte_unmap_unlock(ptep, ptl); +out: + return SWAP_AGAIN; +} + +/* + * Get rid of all migration entries and replace them by + * references to the indicated page. + */ +static void remove_migration_ptes(struct page *old, struct page *new) +{ + rmap_walk(new, remove_migration_pte, old); +} + +/* + * Something used the pte of a page under migration. We need to + * get to the page and wait until migration is finished. + * When we return from this function the fault will be retried. + */ +void migration_entry_wait(struct mm_struct *mm, pmd_t *pmd, + unsigned long address) +{ + pte_t *ptep, pte; + spinlock_t *ptl; + swp_entry_t entry; + struct page *page; + + ptep = pte_offset_map_lock(mm, pmd, address, &ptl); + pte = *ptep; + if (!is_swap_pte(pte)) + goto out; + + entry = pte_to_swp_entry(pte); + if (!is_migration_entry(entry)) + goto out; + + page = migration_entry_to_page(entry); + + /* + * Once radix-tree replacement of page migration started, page_count + * *must* be zero. And, we don't want to call wait_on_page_locked() + * against a page without get_page(). + * So, we use get_page_unless_zero(), here. Even failed, page fault + * will occur again. + */ + if (!get_page_unless_zero(page)) + goto out; + pte_unmap_unlock(ptep, ptl); + wait_on_page_locked(page); + put_page(page); + return; +out: + pte_unmap_unlock(ptep, ptl); +} + +#ifdef CONFIG_BLOCK +/* Returns true if all buffers are successfully locked */ +static bool buffer_migrate_lock_buffers(struct buffer_head *head, + enum migrate_mode mode) +{ + struct buffer_head *bh = head; + + /* Simple case, sync compaction */ + if (mode != MIGRATE_ASYNC) { + do { + get_bh(bh); + lock_buffer(bh); + bh = bh->b_this_page; + + } while (bh != head); + + return true; + } + + /* async case, we cannot block on lock_buffer so use trylock_buffer */ + do { + get_bh(bh); + if (!trylock_buffer(bh)) { + /* + * We failed to lock the buffer and cannot stall in + * async migration. Release the taken locks + */ + struct buffer_head *failed_bh = bh; + put_bh(failed_bh); + bh = head; + while (bh != failed_bh) { + unlock_buffer(bh); + put_bh(bh); + bh = bh->b_this_page; + } + return false; + } + + bh = bh->b_this_page; + } while (bh != head); + return true; +} +#else +static inline bool buffer_migrate_lock_buffers(struct buffer_head *head, + enum migrate_mode mode) +{ + return true; +} +#endif /* CONFIG_BLOCK */ + +/* + * Replace the page in the mapping. + * + * The number of remaining references must be: + * 1 for anonymous pages without a mapping + * 2 for pages with a mapping + * 3 for pages with a mapping and PagePrivate/PagePrivate2 set. + */ +static int migrate_page_move_mapping(struct address_space *mapping, + struct page *newpage, struct page *page, + struct buffer_head *head, enum migrate_mode mode) +{ + int expected_count = 0; + void **pslot; + + if (!mapping) { + /* Anonymous page without mapping */ + if (page_count(page) != 1) + return -EAGAIN; + return MIGRATEPAGE_SUCCESS; + } + + spin_lock_irq(&mapping->tree_lock); + + pslot = radix_tree_lookup_slot(&mapping->page_tree, + page_index(page)); + + expected_count = 2 + page_has_private(page); + if (page_count(page) != expected_count || + radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) { + spin_unlock_irq(&mapping->tree_lock); + return -EAGAIN; + } + + if (!page_freeze_refs(page, expected_count)) { + spin_unlock_irq(&mapping->tree_lock); + return -EAGAIN; + } + + /* + * In the async migration case of moving a page with buffers, lock the + * buffers using trylock before the mapping is moved. If the mapping + * was moved, we later failed to lock the buffers and could not move + * the mapping back due to an elevated page count, we would have to + * block waiting on other references to be dropped. + */ + if (mode == MIGRATE_ASYNC && head && + !buffer_migrate_lock_buffers(head, mode)) { + page_unfreeze_refs(page, expected_count); + spin_unlock_irq(&mapping->tree_lock); + return -EAGAIN; + } + + /* + * Now we know that no one else is looking at the page. + */ + get_page(newpage); /* add cache reference */ + if (PageSwapCache(page)) { + SetPageSwapCache(newpage); + set_page_private(newpage, page_private(page)); + } + + radix_tree_replace_slot(pslot, newpage); + + /* + * Drop cache reference from old page by unfreezing + * to one less reference. + * We know this isn't the last reference. + */ + page_unfreeze_refs(page, expected_count - 1); + + /* + * If moved to a different zone then also account + * the page for that zone. Other VM counters will be + * taken care of when we establish references to the + * new page and drop references to the old page. + * + * Note that anonymous pages are accounted for + * via NR_FILE_PAGES and NR_ANON_PAGES if they + * are mapped to swap space. + */ + __dec_zone_page_state(page, NR_FILE_PAGES); + __inc_zone_page_state(newpage, NR_FILE_PAGES); + if (!PageSwapCache(page) && PageSwapBacked(page)) { + __dec_zone_page_state(page, NR_SHMEM); + __inc_zone_page_state(newpage, NR_SHMEM); + } + spin_unlock_irq(&mapping->tree_lock); + + return MIGRATEPAGE_SUCCESS; +} + +/* + * The expected number of remaining references is the same as that + * of migrate_page_move_mapping(). + */ +int migrate_huge_page_move_mapping(struct address_space *mapping, + struct page *newpage, struct page *page) +{ + int expected_count; + void **pslot; + + if (!mapping) { + if (page_count(page) != 1) + return -EAGAIN; + return MIGRATEPAGE_SUCCESS; + } + + spin_lock_irq(&mapping->tree_lock); + + pslot = radix_tree_lookup_slot(&mapping->page_tree, + page_index(page)); + + expected_count = 2 + page_has_private(page); + if (page_count(page) != expected_count || + radix_tree_deref_slot_protected(pslot, &mapping->tree_lock) != page) { + spin_unlock_irq(&mapping->tree_lock); + return -EAGAIN; + } + + if (!page_freeze_refs(page, expected_count)) { + spin_unlock_irq(&mapping->tree_lock); + return -EAGAIN; + } + + get_page(newpage); + + radix_tree_replace_slot(pslot, newpage); + + page_unfreeze_refs(page, expected_count - 1); + + spin_unlock_irq(&mapping->tree_lock); + return MIGRATEPAGE_SUCCESS; +} + +/* + * Copy the page to its new location + */ +void migrate_page_copy(struct page *newpage, struct page *page) +{ + if (PageHuge(page) || PageTransHuge(page)) + copy_huge_page(newpage, page); + else + copy_highpage(newpage, page); + + if (PageError(page)) + SetPageError(newpage); + if (PageReferenced(page)) + SetPageReferenced(newpage); + if (PageUptodate(page)) + SetPageUptodate(newpage); + if (TestClearPageActive(page)) { + VM_BUG_ON(PageUnevictable(page)); + SetPageActive(newpage); + } else if (TestClearPageUnevictable(page)) + SetPageUnevictable(newpage); + if (PageChecked(page)) + SetPageChecked(newpage); + if (PageMappedToDisk(page)) + SetPageMappedToDisk(newpage); + + if (PageDirty(page)) { + clear_page_dirty_for_io(page); + /* + * Want to mark the page and the radix tree as dirty, and + * redo the accounting that clear_page_dirty_for_io undid, + * but we can't use set_page_dirty because that function + * is actually a signal that all of the page has become dirty. + * Whereas only part of our page may be dirty. + */ + if (PageSwapBacked(page)) + SetPageDirty(newpage); + else + __set_page_dirty_nobuffers(newpage); + } + + mlock_migrate_page(newpage, page); + ksm_migrate_page(newpage, page); + /* + * Please do not reorder this without considering how mm/ksm.c's + * get_ksm_page() depends upon ksm_migrate_page() and PageSwapCache(). + */ + ClearPageSwapCache(page); + ClearPagePrivate(page); + set_page_private(page, 0); + + /* + * If any waiters have accumulated on the new page then + * wake them up. + */ + if (PageWriteback(newpage)) + end_page_writeback(newpage); +} + +/************************************************************ + * Migration functions + ***********************************************************/ + +/* Always fail migration. Used for mappings that are not movable */ +int fail_migrate_page(struct address_space *mapping, + struct page *newpage, struct page *page) +{ + return -EIO; +} +EXPORT_SYMBOL(fail_migrate_page); + +/* + * Common logic to directly migrate a single page suitable for + * pages that do not use PagePrivate/PagePrivate2. + * + * Pages are locked upon entry and exit. + */ +int migrate_page(struct address_space *mapping, + struct page *newpage, struct page *page, + enum migrate_mode mode) +{ + int rc; + + BUG_ON(PageWriteback(page)); /* Writeback must be complete */ + + rc = migrate_page_move_mapping(mapping, newpage, page, NULL, mode); + + if (rc != MIGRATEPAGE_SUCCESS) + return rc; + + migrate_page_copy(newpage, page); + return MIGRATEPAGE_SUCCESS; +} +EXPORT_SYMBOL(migrate_page); + +#ifdef CONFIG_BLOCK +/* + * Migration function for pages with buffers. This function can only be used + * if the underlying filesystem guarantees that no other references to "page" + * exist. + */ +int buffer_migrate_page(struct address_space *mapping, + struct page *newpage, struct page *page, enum migrate_mode mode) +{ + struct buffer_head *bh, *head; + int rc; + + if (!page_has_buffers(page)) + return migrate_page(mapping, newpage, page, mode); + + head = page_buffers(page); + + rc = migrate_page_move_mapping(mapping, newpage, page, head, mode); + + if (rc != MIGRATEPAGE_SUCCESS) + return rc; + + /* + * In the async case, migrate_page_move_mapping locked the buffers + * with an IRQ-safe spinlock held. In the sync case, the buffers + * need to be locked now + */ + if (mode != MIGRATE_ASYNC) + BUG_ON(!buffer_migrate_lock_buffers(head, mode)); + + ClearPagePrivate(page); + set_page_private(newpage, page_private(page)); + set_page_private(page, 0); + put_page(page); + get_page(newpage); + + bh = head; + do { + set_bh_page(bh, newpage, bh_offset(bh)); + bh = bh->b_this_page; + + } while (bh != head); + + SetPagePrivate(newpage); + + migrate_page_copy(newpage, page); + + bh = head; + do { + unlock_buffer(bh); + put_bh(bh); + bh = bh->b_this_page; + + } while (bh != head); + + return MIGRATEPAGE_SUCCESS; +} +EXPORT_SYMBOL(buffer_migrate_page); +#endif + +/* + * Writeback a page to clean the dirty state + */ +static int writeout(struct address_space *mapping, struct page *page) +{ + struct writeback_control wbc = { + .sync_mode = WB_SYNC_NONE, + .nr_to_write = 1, + .range_start = 0, + .range_end = LLONG_MAX, + .for_reclaim = 1 + }; + int rc; + + if (!mapping->a_ops->writepage) + /* No write method for the address space */ + return -EINVAL; + + if (!clear_page_dirty_for_io(page)) + /* Someone else already triggered a write */ + return -EAGAIN; + + /* + * A dirty page may imply that the underlying filesystem has + * the page on some queue. So the page must be clean for + * migration. Writeout may mean we loose the lock and the + * page state is no longer what we checked for earlier. + * At this point we know that the migration attempt cannot + * be successful. + */ + remove_migration_ptes(page, page); + + rc = mapping->a_ops->writepage(page, &wbc); + + if (rc != AOP_WRITEPAGE_ACTIVATE) + /* unlocked. Relock */ + lock_page(page); + + return (rc < 0) ? -EIO : -EAGAIN; +} + +/* + * Default handling if a filesystem does not provide a migration function. + */ +static int fallback_migrate_page(struct address_space *mapping, + struct page *newpage, struct page *page, enum migrate_mode mode) +{ + if (PageDirty(page)) { + /* Only writeback pages in full synchronous migration */ + if (mode != MIGRATE_SYNC) + return -EBUSY; + return writeout(mapping, page); + } + + /* + * Buffers may be managed in a filesystem specific way. + * We must have no buffers or drop them. + */ + if (page_has_private(page) && + !try_to_release_page(page, GFP_KERNEL)) + return -EAGAIN; + + return migrate_page(mapping, newpage, page, mode); +} + +/* + * Move a page to a newly allocated page + * The page is locked and all ptes have been successfully removed. + * + * The new page will have replaced the old page if this function + * is successful. + * + * Return value: + * < 0 - error code + * MIGRATEPAGE_SUCCESS - success + */ +static int move_to_new_page(struct page *newpage, struct page *page, + int remap_swapcache, enum migrate_mode mode) +{ + struct address_space *mapping; + int rc; + + /* + * Block others from accessing the page when we get around to + * establishing additional references. We are the only one + * holding a reference to the new page at this point. + */ + if (!trylock_page(newpage)) + BUG(); + + /* Prepare mapping for the new page.*/ + newpage->index = page->index; + newpage->mapping = page->mapping; + if (PageSwapBacked(page)) + SetPageSwapBacked(newpage); + + mapping = page_mapping(page); + if (!mapping) + rc = migrate_page(mapping, newpage, page, mode); + else if (mapping->a_ops->migratepage) + /* + * Most pages have a mapping and most filesystems provide a + * migratepage callback. Anonymous pages are part of swap + * space which also has its own migratepage callback. This + * is the most common path for page migration. + */ + rc = mapping->a_ops->migratepage(mapping, + newpage, page, mode); + else + rc = fallback_migrate_page(mapping, newpage, page, mode); + + if (rc != MIGRATEPAGE_SUCCESS) { + newpage->mapping = NULL; + } else { + if (remap_swapcache) + remove_migration_ptes(page, newpage); + page->mapping = NULL; + } + + unlock_page(newpage); + + return rc; +} + +static int __unmap_and_move(struct page *page, struct page *newpage, + int force, enum migrate_mode mode) +{ + int rc = -EAGAIN; + int remap_swapcache = 1; + struct mem_cgroup *mem; + struct anon_vma *anon_vma = NULL; + + if (!trylock_page(page)) { + if (!force || mode == MIGRATE_ASYNC) + goto out; + + /* + * It's not safe for direct compaction to call lock_page. + * For example, during page readahead pages are added locked + * to the LRU. Later, when the IO completes the pages are + * marked uptodate and unlocked. However, the queueing + * could be merging multiple pages for one bio (e.g. + * mpage_readpages). If an allocation happens for the + * second or third page, the process can end up locking + * the same page twice and deadlocking. Rather than + * trying to be clever about what pages can be locked, + * avoid the use of lock_page for direct compaction + * altogether. + */ + if (current->flags & PF_MEMALLOC) + goto out; + + lock_page(page); + } + + /* charge against new page */ + mem_cgroup_prepare_migration(page, newpage, &mem); + + if (PageWriteback(page)) { + /* + * Only in the case of a full syncronous migration is it + * necessary to wait for PageWriteback. In the async case, + * the retry loop is too short and in the sync-light case, + * the overhead of stalling is too much + */ + if (mode != MIGRATE_SYNC) { + rc = -EBUSY; + goto uncharge; + } + if (!force) + goto uncharge; + wait_on_page_writeback(page); + } + /* + * By try_to_unmap(), page->mapcount goes down to 0 here. In this case, + * we cannot notice that anon_vma is freed while we migrates a page. + * This get_anon_vma() delays freeing anon_vma pointer until the end + * of migration. File cache pages are no problem because of page_lock() + * File Caches may use write_page() or lock_page() in migration, then, + * just care Anon page here. + */ + if (PageAnon(page) && !PageKsm(page)) { + /* + * Only page_lock_anon_vma_read() understands the subtleties of + * getting a hold on an anon_vma from outside one of its mms. + */ + anon_vma = page_get_anon_vma(page); + if (anon_vma) { + /* + * Anon page + */ + } else if (PageSwapCache(page)) { + /* + * We cannot be sure that the anon_vma of an unmapped + * swapcache page is safe to use because we don't + * know in advance if the VMA that this page belonged + * to still exists. If the VMA and others sharing the + * data have been freed, then the anon_vma could + * already be invalid. + * + * To avoid this possibility, swapcache pages get + * migrated but are not remapped when migration + * completes + */ + remap_swapcache = 0; + } else { + goto uncharge; + } + } + + if (unlikely(balloon_page_movable(page))) { + /* + * A ballooned page does not need any special attention from + * physical to virtual reverse mapping procedures. + * Skip any attempt to unmap PTEs or to remap swap cache, + * in order to avoid burning cycles at rmap level, and perform + * the page migration right away (proteced by page lock). + */ + rc = balloon_page_migrate(newpage, page, mode); + goto uncharge; + } + + /* + * Corner case handling: + * 1. When a new swap-cache page is read into, it is added to the LRU + * and treated as swapcache but it has no rmap yet. + * Calling try_to_unmap() against a page->mapping==NULL page will + * trigger a BUG. So handle it here. + * 2. An orphaned page (see truncate_complete_page) might have + * fs-private metadata. The page can be picked up due to memory + * offlining. Everywhere else except page reclaim, the page is + * invisible to the vm, so the page can not be migrated. So try to + * free the metadata, so the page can be freed. + */ + if (!page->mapping) { + VM_BUG_ON(PageAnon(page)); + if (page_has_private(page)) { + try_to_free_buffers(page); + goto uncharge; + } + goto skip_unmap; + } + + /* Establish migration ptes or remove ptes */ + try_to_unmap(page, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS); + +skip_unmap: + if (!page_mapped(page)) + rc = move_to_new_page(newpage, page, remap_swapcache, mode); + + if (rc && remap_swapcache) + remove_migration_ptes(page, page); + + /* Drop an anon_vma reference if we took one */ + if (anon_vma) + put_anon_vma(anon_vma); + +uncharge: + mem_cgroup_end_migration(mem, page, newpage, + (rc == MIGRATEPAGE_SUCCESS || + rc == MIGRATEPAGE_BALLOON_SUCCESS)); + unlock_page(page); +out: + return rc; +} + +/* + * Obtain the lock on page, remove all ptes and migrate the page + * to the newly allocated page in newpage. + */ +static int unmap_and_move(new_page_t get_new_page, unsigned long private, + struct page *page, int force, enum migrate_mode mode) +{ + int rc = 0; + int *result = NULL; + struct page *newpage = get_new_page(page, private, &result); + + if (!newpage) + return -ENOMEM; + + if (page_count(page) == 1) { + /* page was freed from under us. So we are done. */ + goto out; + } + + if (unlikely(PageTransHuge(page))) + if (unlikely(split_huge_page(page))) + goto out; + + rc = __unmap_and_move(page, newpage, force, mode); + + if (unlikely(rc == MIGRATEPAGE_BALLOON_SUCCESS)) { + /* + * A ballooned page has been migrated already. + * Now, it's the time to wrap-up counters, + * handle the page back to Buddy and return. + */ + dec_zone_page_state(page, NR_ISOLATED_ANON + + page_is_file_cache(page)); + balloon_page_free(page); + return MIGRATEPAGE_SUCCESS; + } +out: + if (rc != -EAGAIN) { + /* + * A page that has been migrated has all references + * removed and will be freed. A page that has not been + * migrated will have kepts its references and be + * restored. + */ + list_del(&page->lru); + dec_zone_page_state(page, NR_ISOLATED_ANON + + page_is_file_cache(page)); + putback_lru_page(page); + } + /* + * Move the new page to the LRU. If migration was not successful + * then this will free the page. + */ + putback_lru_page(newpage); + if (result) { + if (rc) + *result = rc; + else + *result = page_to_nid(newpage); + } + return rc; +} + +/* + * Counterpart of unmap_and_move_page() for hugepage migration. + * + * This function doesn't wait the completion of hugepage I/O + * because there is no race between I/O and migration for hugepage. + * Note that currently hugepage I/O occurs only in direct I/O + * where no lock is held and PG_writeback is irrelevant, + * and writeback status of all subpages are counted in the reference + * count of the head page (i.e. if all subpages of a 2MB hugepage are + * under direct I/O, the reference of the head page is 512 and a bit more.) + * This means that when we try to migrate hugepage whose subpages are + * doing direct I/O, some references remain after try_to_unmap() and + * hugepage migration fails without data corruption. + * + * There is also no race when direct I/O is issued on the page under migration, + * because then pte is replaced with migration swap entry and direct I/O code + * will wait in the page fault for migration to complete. + */ +static int unmap_and_move_huge_page(new_page_t get_new_page, + unsigned long private, struct page *hpage, + int force, enum migrate_mode mode) +{ + int rc = 0; + int *result = NULL; + struct page *new_hpage = get_new_page(hpage, private, &result); + struct anon_vma *anon_vma = NULL; + + if (!new_hpage) + return -ENOMEM; + + rc = -EAGAIN; + + if (!trylock_page(hpage)) { + if (!force || mode != MIGRATE_SYNC) + goto out; + lock_page(hpage); + } + + if (PageAnon(hpage)) + anon_vma = page_get_anon_vma(hpage); + + try_to_unmap(hpage, TTU_MIGRATION|TTU_IGNORE_MLOCK|TTU_IGNORE_ACCESS); + + if (!page_mapped(hpage)) + rc = move_to_new_page(new_hpage, hpage, 1, mode); + + if (rc) + remove_migration_ptes(hpage, hpage); + + if (anon_vma) + put_anon_vma(anon_vma); + + if (!rc) + hugetlb_cgroup_migrate(hpage, new_hpage); + + unlock_page(hpage); +out: + put_page(new_hpage); + if (result) { + if (rc) + *result = rc; + else + *result = page_to_nid(new_hpage); + } + return rc; +} + +/* + * migrate_pages + * + * The function takes one list of pages to migrate and a function + * that determines from the page to be migrated and the private data + * the target of the move and allocates the page. + * + * The function returns after 10 attempts or if no pages + * are movable anymore because to has become empty + * or no retryable pages exist anymore. + * Caller should call putback_lru_pages to return pages to the LRU + * or free list only if ret != 0. + * + * Return: Number of pages not migrated or error code. + */ +int migrate_pages(struct list_head *from, new_page_t get_new_page, + unsigned long private, enum migrate_mode mode, int reason) +{ + int retry = 1; + int nr_failed = 0; + int nr_succeeded = 0; + int pass = 0; + struct page *page; + struct page *page2; + int swapwrite = current->flags & PF_SWAPWRITE; + int rc; + + if (!swapwrite) + current->flags |= PF_SWAPWRITE; + + for(pass = 0; pass < 10 && retry; pass++) { + retry = 0; + + list_for_each_entry_safe(page, page2, from, lru) { + cond_resched(); + + rc = unmap_and_move(get_new_page, private, + page, pass > 2, mode); + + switch(rc) { + case -ENOMEM: + goto out; + case -EAGAIN: + retry++; + break; + case MIGRATEPAGE_SUCCESS: + nr_succeeded++; + break; + default: + /* Permanent failure */ + nr_failed++; + break; + } + } + } + rc = nr_failed + retry; +out: + if (nr_succeeded) + count_vm_events(PGMIGRATE_SUCCESS, nr_succeeded); + if (nr_failed) + count_vm_events(PGMIGRATE_FAIL, nr_failed); + trace_mm_migrate_pages(nr_succeeded, nr_failed, mode, reason); + + if (!swapwrite) + current->flags &= ~PF_SWAPWRITE; + + return rc; +} + +int migrate_huge_page(struct page *hpage, new_page_t get_new_page, + unsigned long private, enum migrate_mode mode) +{ + int pass, rc; + + for (pass = 0; pass < 10; pass++) { + rc = unmap_and_move_huge_page(get_new_page, private, + hpage, pass > 2, mode); + switch (rc) { + case -ENOMEM: + goto out; + case -EAGAIN: + /* try again */ + cond_resched(); + break; + case MIGRATEPAGE_SUCCESS: + goto out; + default: + rc = -EIO; + goto out; + } + } +out: + return rc; +} + +#ifdef CONFIG_NUMA +/* + * Move a list of individual pages + */ +struct page_to_node { + unsigned long addr; + struct page *page; + int node; + int status; +}; + +static struct page *new_page_node(struct page *p, unsigned long private, + int **result) +{ + struct page_to_node *pm = (struct page_to_node *)private; + + while (pm->node != MAX_NUMNODES && pm->page != p) + pm++; + + if (pm->node == MAX_NUMNODES) + return NULL; + + *result = &pm->status; + + return alloc_pages_exact_node(pm->node, + GFP_HIGHUSER_MOVABLE | GFP_THISNODE, 0); +} + +/* + * Move a set of pages as indicated in the pm array. The addr + * field must be set to the virtual address of the page to be moved + * and the node number must contain a valid target node. + * The pm array ends with node = MAX_NUMNODES. + */ +static int do_move_page_to_node_array(struct mm_struct *mm, + struct page_to_node *pm, + int migrate_all) +{ + int err; + struct page_to_node *pp; + LIST_HEAD(pagelist); + + down_read(&mm->mmap_sem); + + /* + * Build a list of pages to migrate + */ + for (pp = pm; pp->node != MAX_NUMNODES; pp++) { + struct vm_area_struct *vma; + struct page *page; + + err = -EFAULT; + vma = find_vma(mm, pp->addr); + if (!vma || pp->addr < vma->vm_start || !vma_migratable(vma)) + goto set_status; + + page = follow_page(vma, pp->addr, FOLL_GET|FOLL_SPLIT); + + err = PTR_ERR(page); + if (IS_ERR(page)) + goto set_status; + + err = -ENOENT; + if (!page) + goto set_status; + + /* Use PageReserved to check for zero page */ + if (PageReserved(page)) + goto put_and_set; + + pp->page = page; + err = page_to_nid(page); + + if (err == pp->node) + /* + * Node already in the right place + */ + goto put_and_set; + + err = -EACCES; + if (page_mapcount(page) > 1 && + !migrate_all) + goto put_and_set; + + err = isolate_lru_page(page); + if (!err) { + list_add_tail(&page->lru, &pagelist); + inc_zone_page_state(page, NR_ISOLATED_ANON + + page_is_file_cache(page)); + } +put_and_set: + /* + * Either remove the duplicate refcount from + * isolate_lru_page() or drop the page ref if it was + * not isolated. + */ + put_page(page); +set_status: + pp->status = err; + } + + err = 0; + if (!list_empty(&pagelist)) { + err = migrate_pages(&pagelist, new_page_node, + (unsigned long)pm, MIGRATE_SYNC, MR_SYSCALL); + if (err) + putback_lru_pages(&pagelist); + } + + up_read(&mm->mmap_sem); + return err; +} + +/* + * Migrate an array of page address onto an array of nodes and fill + * the corresponding array of status. + */ +static int do_pages_move(struct mm_struct *mm, nodemask_t task_nodes, + unsigned long nr_pages, + const void __user * __user *pages, + const int __user *nodes, + int __user *status, int flags) +{ + struct page_to_node *pm; + unsigned long chunk_nr_pages; + unsigned long chunk_start; + int err; + + err = -ENOMEM; + pm = (struct page_to_node *)__get_free_page(GFP_KERNEL); + if (!pm) + goto out; + + migrate_prep(); + + /* + * Store a chunk of page_to_node array in a page, + * but keep the last one as a marker + */ + chunk_nr_pages = (PAGE_SIZE / sizeof(struct page_to_node)) - 1; + + for (chunk_start = 0; + chunk_start < nr_pages; + chunk_start += chunk_nr_pages) { + int j; + + if (chunk_start + chunk_nr_pages > nr_pages) + chunk_nr_pages = nr_pages - chunk_start; + + /* fill the chunk pm with addrs and nodes from user-space */ + for (j = 0; j < chunk_nr_pages; j++) { + const void __user *p; + int node; + + err = -EFAULT; + if (get_user(p, pages + j + chunk_start)) + goto out_pm; + pm[j].addr = (unsigned long) p; + + if (get_user(node, nodes + j + chunk_start)) + goto out_pm; + + err = -ENODEV; + if (node < 0 || node >= MAX_NUMNODES) + goto out_pm; + + if (!node_state(node, N_MEMORY)) + goto out_pm; + + err = -EACCES; + if (!node_isset(node, task_nodes)) + goto out_pm; + + pm[j].node = node; + } + + /* End marker for this chunk */ + pm[chunk_nr_pages].node = MAX_NUMNODES; + + /* Migrate this chunk */ + err = do_move_page_to_node_array(mm, pm, + flags & MPOL_MF_MOVE_ALL); + if (err < 0) + goto out_pm; + + /* Return status information */ + for (j = 0; j < chunk_nr_pages; j++) + if (put_user(pm[j].status, status + j + chunk_start)) { + err = -EFAULT; + goto out_pm; + } + } + err = 0; + +out_pm: + free_page((unsigned long)pm); +out: + return err; +} + +/* + * Determine the nodes of an array of pages and store it in an array of status. + */ +static void do_pages_stat_array(struct mm_struct *mm, unsigned long nr_pages, + const void __user **pages, int *status) +{ + unsigned long i; + + down_read(&mm->mmap_sem); + + for (i = 0; i < nr_pages; i++) { + unsigned long addr = (unsigned long)(*pages); + struct vm_area_struct *vma; + struct page *page; + int err = -EFAULT; + + vma = find_vma(mm, addr); + if (!vma || addr < vma->vm_start) + goto set_status; + + page = follow_page(vma, addr, 0); + + err = PTR_ERR(page); + if (IS_ERR(page)) + goto set_status; + + err = -ENOENT; + /* Use PageReserved to check for zero page */ + if (!page || PageReserved(page)) + goto set_status; + + err = page_to_nid(page); +set_status: + *status = err; + + pages++; + status++; + } + + up_read(&mm->mmap_sem); +} + +/* + * Determine the nodes of a user array of pages and store it in + * a user array of status. + */ +static int do_pages_stat(struct mm_struct *mm, unsigned long nr_pages, + const void __user * __user *pages, + int __user *status) +{ +#define DO_PAGES_STAT_CHUNK_NR 16 + const void __user *chunk_pages[DO_PAGES_STAT_CHUNK_NR]; + int chunk_status[DO_PAGES_STAT_CHUNK_NR]; + + while (nr_pages) { + unsigned long chunk_nr; + + chunk_nr = nr_pages; + if (chunk_nr > DO_PAGES_STAT_CHUNK_NR) + chunk_nr = DO_PAGES_STAT_CHUNK_NR; + + if (copy_from_user(chunk_pages, pages, chunk_nr * sizeof(*chunk_pages))) + break; + + do_pages_stat_array(mm, chunk_nr, chunk_pages, chunk_status); + + if (copy_to_user(status, chunk_status, chunk_nr * sizeof(*status))) + break; + + pages += chunk_nr; + status += chunk_nr; + nr_pages -= chunk_nr; + } + return nr_pages ? -EFAULT : 0; +} + +/* + * Move a list of pages in the address space of the currently executing + * process. + */ +SYSCALL_DEFINE6(move_pages, pid_t, pid, unsigned long, nr_pages, + const void __user * __user *, pages, + const int __user *, nodes, + int __user *, status, int, flags) +{ + const struct cred *cred = current_cred(), *tcred; + struct task_struct *task; + struct mm_struct *mm; + int err; + nodemask_t task_nodes; + + /* Check flags */ + if (flags & ~(MPOL_MF_MOVE|MPOL_MF_MOVE_ALL)) + return -EINVAL; + + if ((flags & MPOL_MF_MOVE_ALL) && !capable(CAP_SYS_NICE)) + return -EPERM; + + /* Find the mm_struct */ + rcu_read_lock(); + task = pid ? find_task_by_vpid(pid) : current; + if (!task) { + rcu_read_unlock(); + return -ESRCH; + } + get_task_struct(task); + + /* + * Check if this process has the right to modify the specified + * process. The right exists if the process has administrative + * capabilities, superuser privileges or the same + * userid as the target process. + */ + tcred = __task_cred(task); + if (!uid_eq(cred->euid, tcred->suid) && !uid_eq(cred->euid, tcred->uid) && + !uid_eq(cred->uid, tcred->suid) && !uid_eq(cred->uid, tcred->uid) && + !capable(CAP_SYS_NICE)) { + rcu_read_unlock(); + err = -EPERM; + goto out; + } + rcu_read_unlock(); + + err = security_task_movememory(task); + if (err) + goto out; + + task_nodes = cpuset_mems_allowed(task); + mm = get_task_mm(task); + put_task_struct(task); + + if (!mm) + return -EINVAL; + + if (nodes) + err = do_pages_move(mm, task_nodes, nr_pages, pages, + nodes, status, flags); + else + err = do_pages_stat(mm, nr_pages, pages, status); + + mmput(mm); + return err; + +out: + put_task_struct(task); + return err; +} + +/* + * Call migration functions in the vma_ops that may prepare + * memory in a vm for migration. migration functions may perform + * the migration for vmas that do not have an underlying page struct. + */ +int migrate_vmas(struct mm_struct *mm, const nodemask_t *to, + const nodemask_t *from, unsigned long flags) +{ + struct vm_area_struct *vma; + int err = 0; + + for (vma = mm->mmap; vma && !err; vma = vma->vm_next) { + if (vma->vm_ops && vma->vm_ops->migrate) { + err = vma->vm_ops->migrate(vma, to, from, flags); + if (err) + break; + } + } + return err; +} + +#ifdef CONFIG_NUMA_BALANCING +/* + * Returns true if this is a safe migration target node for misplaced NUMA + * pages. Currently it only checks the watermarks which crude + */ +static bool migrate_balanced_pgdat(struct pglist_data *pgdat, + unsigned long nr_migrate_pages) +{ + int z; + for (z = pgdat->nr_zones - 1; z >= 0; z--) { + struct zone *zone = pgdat->node_zones + z; + + if (!populated_zone(zone)) + continue; + + if (zone->all_unreclaimable) + continue; + + /* Avoid waking kswapd by allocating pages_to_migrate pages. */ + if (!zone_watermark_ok(zone, 0, + high_wmark_pages(zone) + + nr_migrate_pages, + 0, 0)) + continue; + return true; + } + return false; +} + +static struct page *alloc_misplaced_dst_page(struct page *page, + unsigned long data, + int **result) +{ + int nid = (int) data; + struct page *newpage; + + newpage = alloc_pages_exact_node(nid, + (GFP_HIGHUSER_MOVABLE | GFP_THISNODE | + __GFP_NOMEMALLOC | __GFP_NORETRY | + __GFP_NOWARN) & + ~GFP_IOFS, 0); + if (newpage) + page_nid_xchg_last(newpage, page_nid_last(page)); + + return newpage; +} + +/* + * page migration rate limiting control. + * Do not migrate more than @pages_to_migrate in a @migrate_interval_millisecs + * window of time. Default here says do not migrate more than 1280M per second. + * If a node is rate-limited then PTE NUMA updates are also rate-limited. However + * as it is faults that reset the window, pte updates will happen unconditionally + * if there has not been a fault since @pteupdate_interval_millisecs after the + * throttle window closed. + */ +static unsigned int migrate_interval_millisecs __read_mostly = 100; +static unsigned int pteupdate_interval_millisecs __read_mostly = 1000; +static unsigned int ratelimit_pages __read_mostly = 128 << (20 - PAGE_SHIFT); + +/* Returns true if NUMA migration is currently rate limited */ +bool migrate_ratelimited(int node) +{ + pg_data_t *pgdat = NODE_DATA(node); + + if (time_after(jiffies, pgdat->numabalancing_migrate_next_window + + msecs_to_jiffies(pteupdate_interval_millisecs))) + return false; + + if (pgdat->numabalancing_migrate_nr_pages < ratelimit_pages) + return false; + + return true; +} + +/* Returns true if the node is migrate rate-limited after the update */ +bool numamigrate_update_ratelimit(pg_data_t *pgdat, unsigned long nr_pages) +{ + bool rate_limited = false; + + /* + * Rate-limit the amount of data that is being migrated to a node. + * Optimal placement is no good if the memory bus is saturated and + * all the time is being spent migrating! + */ + spin_lock(&pgdat->numabalancing_migrate_lock); + if (time_after(jiffies, pgdat->numabalancing_migrate_next_window)) { + pgdat->numabalancing_migrate_nr_pages = 0; + pgdat->numabalancing_migrate_next_window = jiffies + + msecs_to_jiffies(migrate_interval_millisecs); + } + if (pgdat->numabalancing_migrate_nr_pages > ratelimit_pages) + rate_limited = true; + else + pgdat->numabalancing_migrate_nr_pages += nr_pages; + spin_unlock(&pgdat->numabalancing_migrate_lock); + + return rate_limited; +} + +int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page) +{ + int page_lru; + + VM_BUG_ON(compound_order(page) && !PageTransHuge(page)); + + /* Avoid migrating to a node that is nearly full */ + if (!migrate_balanced_pgdat(pgdat, 1UL << compound_order(page))) + return 0; + + if (isolate_lru_page(page)) + return 0; + + /* + * migrate_misplaced_transhuge_page() skips page migration's usual + * check on page_count(), so we must do it here, now that the page + * has been isolated: a GUP pin, or any other pin, prevents migration. + * The expected page count is 3: 1 for page's mapcount and 1 for the + * caller's pin and 1 for the reference taken by isolate_lru_page(). + */ + if (PageTransHuge(page) && page_count(page) != 3) { + putback_lru_page(page); + return 0; + } + + page_lru = page_is_file_cache(page); + mod_zone_page_state(page_zone(page), NR_ISOLATED_ANON + page_lru, + hpage_nr_pages(page)); + + /* + * Isolating the page has taken another reference, so the + * caller's reference can be safely dropped without the page + * disappearing underneath us during migration. + */ + put_page(page); + return 1; +} + +/* + * Attempt to migrate a misplaced page to the specified destination + * node. Caller is expected to have an elevated reference count on + * the page that will be dropped by this function before returning. + */ +int migrate_misplaced_page(struct page *page, int node) +{ + pg_data_t *pgdat = NODE_DATA(node); + int isolated; + int nr_remaining; + LIST_HEAD(migratepages); + + /* + * Don't migrate pages that are mapped in multiple processes. + * TODO: Handle false sharing detection instead of this hammer + */ + if (page_mapcount(page) != 1) + goto out; + + /* + * Rate-limit the amount of data that is being migrated to a node. + * Optimal placement is no good if the memory bus is saturated and + * all the time is being spent migrating! + */ + if (numamigrate_update_ratelimit(pgdat, 1)) + goto out; + + isolated = numamigrate_isolate_page(pgdat, page); + if (!isolated) + goto out; + + list_add(&page->lru, &migratepages); + nr_remaining = migrate_pages(&migratepages, alloc_misplaced_dst_page, + node, MIGRATE_ASYNC, MR_NUMA_MISPLACED); + if (nr_remaining) { + putback_lru_pages(&migratepages); + isolated = 0; + } else + count_vm_numa_event(NUMA_PAGE_MIGRATE); + BUG_ON(!list_empty(&migratepages)); + return isolated; + +out: + put_page(page); + return 0; +} +#endif /* CONFIG_NUMA_BALANCING */ + +#if defined(CONFIG_NUMA_BALANCING) && defined(CONFIG_TRANSPARENT_HUGEPAGE) +/* + * Migrates a THP to a given target node. page must be locked and is unlocked + * before returning. + */ +int migrate_misplaced_transhuge_page(struct mm_struct *mm, + struct vm_area_struct *vma, + pmd_t *pmd, pmd_t entry, + unsigned long address, + struct page *page, int node) +{ + unsigned long haddr = address & HPAGE_PMD_MASK; + pg_data_t *pgdat = NODE_DATA(node); + int isolated = 0; + struct page *new_page = NULL; + struct mem_cgroup *memcg = NULL; + int page_lru = page_is_file_cache(page); + + /* + * Don't migrate pages that are mapped in multiple processes. + * TODO: Handle false sharing detection instead of this hammer + */ + if (page_mapcount(page) != 1) + goto out_dropref; + + /* + * Rate-limit the amount of data that is being migrated to a node. + * Optimal placement is no good if the memory bus is saturated and + * all the time is being spent migrating! + */ + if (numamigrate_update_ratelimit(pgdat, HPAGE_PMD_NR)) + goto out_dropref; + + new_page = alloc_pages_node(node, + (GFP_TRANSHUGE | GFP_THISNODE) & ~__GFP_WAIT, HPAGE_PMD_ORDER); + if (!new_page) + goto out_fail; + + page_nid_xchg_last(new_page, page_nid_last(page)); + + isolated = numamigrate_isolate_page(pgdat, page); + if (!isolated) { + put_page(new_page); + goto out_fail; + } + + /* Prepare a page as a migration target */ + __set_page_locked(new_page); + SetPageSwapBacked(new_page); + + /* anon mapping, we can simply copy page->mapping to the new page: */ + new_page->mapping = page->mapping; + new_page->index = page->index; + migrate_page_copy(new_page, page); + WARN_ON(PageLRU(new_page)); + + /* Recheck the target PMD */ + spin_lock(&mm->page_table_lock); + if (unlikely(!pmd_same(*pmd, entry))) { + spin_unlock(&mm->page_table_lock); + + /* Reverse changes made by migrate_page_copy() */ + if (TestClearPageActive(new_page)) + SetPageActive(page); + if (TestClearPageUnevictable(new_page)) + SetPageUnevictable(page); + mlock_migrate_page(page, new_page); + + unlock_page(new_page); + put_page(new_page); /* Free it */ + + unlock_page(page); + putback_lru_page(page); + + count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR); + isolated = 0; + goto out; + } + + /* + * Traditional migration needs to prepare the memcg charge + * transaction early to prevent the old page from being + * uncharged when installing migration entries. Here we can + * save the potential rollback and start the charge transfer + * only when migration is already known to end successfully. + */ + mem_cgroup_prepare_migration(page, new_page, &memcg); + + entry = mk_pmd(new_page, vma->vm_page_prot); + entry = pmd_mknonnuma(entry); + entry = maybe_pmd_mkwrite(pmd_mkdirty(entry), vma); + entry = pmd_mkhuge(entry); + + page_add_new_anon_rmap(new_page, vma, haddr); + + set_pmd_at(mm, haddr, pmd, entry); + update_mmu_cache_pmd(vma, address, &entry); + page_remove_rmap(page); + /* + * Finish the charge transaction under the page table lock to + * prevent split_huge_page() from dividing up the charge + * before it's fully transferred to the new page. + */ + mem_cgroup_end_migration(memcg, page, new_page, true); + spin_unlock(&mm->page_table_lock); + + unlock_page(new_page); + unlock_page(page); + put_page(page); /* Drop the rmap reference */ + put_page(page); /* Drop the LRU isolation reference */ + + count_vm_events(PGMIGRATE_SUCCESS, HPAGE_PMD_NR); + count_vm_numa_events(NUMA_PAGE_MIGRATE, HPAGE_PMD_NR); + +out: + mod_zone_page_state(page_zone(page), + NR_ISOLATED_ANON + page_lru, + -HPAGE_PMD_NR); + return isolated; + +out_fail: + count_vm_events(PGMIGRATE_FAIL, HPAGE_PMD_NR); +out_dropref: + unlock_page(page); + put_page(page); + return 0; +} +#endif /* CONFIG_NUMA_BALANCING */ + +#endif /* CONFIG_NUMA */ |