diff options
Diffstat (limited to 'mm/huge_memory.c')
| -rw-r--r-- | mm/huge_memory.c | 359 |
1 files changed, 333 insertions, 26 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c index 5f902e20e8c0..827d9c813051 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -12,12 +12,14 @@ #include <linux/mmu_notifier.h> #include <linux/rmap.h> #include <linux/swap.h> +#include <linux/shrinker.h> #include <linux/mm_inline.h> #include <linux/kthread.h> #include <linux/khugepaged.h> #include <linux/freezer.h> #include <linux/mman.h> #include <linux/pagemap.h> + #include <asm/tlb.h> #include <asm/pgalloc.h> #include "internal.h" @@ -37,7 +39,8 @@ unsigned long transparent_hugepage_flags __read_mostly = (1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)| #endif (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)| - (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); + (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG)| + (1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); /* default scan 8*512 pte (or vmas) every 30 second */ static unsigned int khugepaged_pages_to_scan __read_mostly = HPAGE_PMD_NR*8; @@ -159,6 +162,77 @@ static int start_khugepaged(void) return err; } +static atomic_t huge_zero_refcount; +static unsigned long huge_zero_pfn __read_mostly; + +static inline bool is_huge_zero_pfn(unsigned long pfn) +{ + unsigned long zero_pfn = ACCESS_ONCE(huge_zero_pfn); + return zero_pfn && pfn == zero_pfn; +} + +static inline bool is_huge_zero_pmd(pmd_t pmd) +{ + return is_huge_zero_pfn(pmd_pfn(pmd)); +} + +static unsigned long get_huge_zero_page(void) +{ + struct page *zero_page; +retry: + if (likely(atomic_inc_not_zero(&huge_zero_refcount))) + return ACCESS_ONCE(huge_zero_pfn); + + zero_page = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE, + HPAGE_PMD_ORDER); + if (!zero_page) { + count_vm_event(THP_ZERO_PAGE_ALLOC_FAILED); + return 0; + } + count_vm_event(THP_ZERO_PAGE_ALLOC); + preempt_disable(); + if (cmpxchg(&huge_zero_pfn, 0, page_to_pfn(zero_page))) { + preempt_enable(); + __free_page(zero_page); + goto retry; + } + + /* We take additional reference here. It will be put back by shrinker */ + atomic_set(&huge_zero_refcount, 2); + preempt_enable(); + return ACCESS_ONCE(huge_zero_pfn); +} + +static void put_huge_zero_page(void) +{ + /* + * Counter should never go to zero here. Only shrinker can put + * last reference. + */ + BUG_ON(atomic_dec_and_test(&huge_zero_refcount)); +} + +static int shrink_huge_zero_page(struct shrinker *shrink, + struct shrink_control *sc) +{ + if (!sc->nr_to_scan) + /* we can free zero page only if last reference remains */ + return atomic_read(&huge_zero_refcount) == 1 ? HPAGE_PMD_NR : 0; + + if (atomic_cmpxchg(&huge_zero_refcount, 1, 0) == 1) { + unsigned long zero_pfn = xchg(&huge_zero_pfn, 0); + BUG_ON(zero_pfn == 0); + __free_page(__pfn_to_page(zero_pfn)); + } + + return 0; +} + +static struct shrinker huge_zero_page_shrinker = { + .shrink = shrink_huge_zero_page, + .seeks = DEFAULT_SEEKS, +}; + #ifdef CONFIG_SYSFS static ssize_t double_flag_show(struct kobject *kobj, @@ -284,6 +358,20 @@ static ssize_t defrag_store(struct kobject *kobj, static struct kobj_attribute defrag_attr = __ATTR(defrag, 0644, defrag_show, defrag_store); +static ssize_t use_zero_page_show(struct kobject *kobj, + struct kobj_attribute *attr, char *buf) +{ + return single_flag_show(kobj, attr, buf, + TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); +} +static ssize_t use_zero_page_store(struct kobject *kobj, + struct kobj_attribute *attr, const char *buf, size_t count) +{ + return single_flag_store(kobj, attr, buf, count, + TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG); +} +static struct kobj_attribute use_zero_page_attr = + __ATTR(use_zero_page, 0644, use_zero_page_show, use_zero_page_store); #ifdef CONFIG_DEBUG_VM static ssize_t debug_cow_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf) @@ -305,6 +393,7 @@ static struct kobj_attribute debug_cow_attr = static struct attribute *hugepage_attr[] = { &enabled_attr.attr, &defrag_attr.attr, + &use_zero_page_attr.attr, #ifdef CONFIG_DEBUG_VM &debug_cow_attr.attr, #endif @@ -550,6 +639,8 @@ static int __init hugepage_init(void) goto out; } + register_shrinker(&huge_zero_page_shrinker); + /* * By default disable transparent hugepages on smaller systems, * where the extra memory used could hurt more than TLB overhead @@ -678,6 +769,22 @@ static inline struct page *alloc_hugepage(int defrag) } #endif +static bool set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm, + struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd, + unsigned long zero_pfn) +{ + pmd_t entry; + if (!pmd_none(*pmd)) + return false; + entry = pfn_pmd(zero_pfn, vma->vm_page_prot); + entry = pmd_wrprotect(entry); + entry = pmd_mkhuge(entry); + set_pmd_at(mm, haddr, pmd, entry); + pgtable_trans_huge_deposit(mm, pgtable); + mm->nr_ptes++; + return true; +} + int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, pmd_t *pmd, unsigned int flags) @@ -691,6 +798,30 @@ int do_huge_pmd_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma, return VM_FAULT_OOM; if (unlikely(khugepaged_enter(vma))) return VM_FAULT_OOM; + if (!(flags & FAULT_FLAG_WRITE) && + transparent_hugepage_use_zero_page()) { + pgtable_t pgtable; + unsigned long zero_pfn; + bool set; + pgtable = pte_alloc_one(mm, haddr); + if (unlikely(!pgtable)) + return VM_FAULT_OOM; + zero_pfn = get_huge_zero_page(); + if (unlikely(!zero_pfn)) { + pte_free(mm, pgtable); + count_vm_event(THP_FAULT_FALLBACK); + goto out; + } + spin_lock(&mm->page_table_lock); + set = set_huge_zero_page(pgtable, mm, vma, haddr, pmd, + zero_pfn); + spin_unlock(&mm->page_table_lock); + if (!set) { + pte_free(mm, pgtable); + put_huge_zero_page(); + } + return 0; + } page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), vma, haddr, numa_node_id(), 0); if (unlikely(!page)) { @@ -755,6 +886,26 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm, pte_free(dst_mm, pgtable); goto out_unlock; } + /* + * mm->page_table_lock is enough to be sure that huge zero pmd is not + * under splitting since we don't split the page itself, only pmd to + * a page table. + */ + if (is_huge_zero_pmd(pmd)) { + unsigned long zero_pfn; + bool set; + /* + * get_huge_zero_page() will never allocate a new page here, + * since we already have a zero page to copy. It just takes a + * reference. + */ + zero_pfn = get_huge_zero_page(); + set = set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_pmd, + zero_pfn); + BUG_ON(!set); /* unexpected !pmd_none(dst_pmd) */ + ret = 0; + goto out_unlock; + } if (unlikely(pmd_trans_splitting(pmd))) { /* split huge page running from under us */ spin_unlock(&src_mm->page_table_lock); @@ -806,6 +957,80 @@ unlock: spin_unlock(&mm->page_table_lock); } +static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm, + struct vm_area_struct *vma, unsigned long address, + pmd_t *pmd, pmd_t orig_pmd, unsigned long haddr) +{ + pgtable_t pgtable; + pmd_t _pmd; + struct page *page; + int i, ret = 0; + unsigned long mmun_start; /* For mmu_notifiers */ + unsigned long mmun_end; /* For mmu_notifiers */ + + page = alloc_page_vma(GFP_HIGHUSER_MOVABLE, vma, address); + if (!page) { + ret |= VM_FAULT_OOM; + goto out; + } + + if (mem_cgroup_newpage_charge(page, mm, GFP_KERNEL)) { + put_page(page); + ret |= VM_FAULT_OOM; + goto out; + } + + clear_user_highpage(page, address); + __SetPageUptodate(page); + + mmun_start = haddr; + mmun_end = haddr + HPAGE_PMD_SIZE; + mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); + + spin_lock(&mm->page_table_lock); + if (unlikely(!pmd_same(*pmd, orig_pmd))) + goto out_free_page; + + pmdp_clear_flush(vma, haddr, pmd); + /* leave pmd empty until pte is filled */ + + pgtable = pgtable_trans_huge_withdraw(mm); + pmd_populate(mm, &_pmd, pgtable); + + for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { + pte_t *pte, entry; + if (haddr == (address & PAGE_MASK)) { + entry = mk_pte(page, vma->vm_page_prot); + entry = maybe_mkwrite(pte_mkdirty(entry), vma); + page_add_new_anon_rmap(page, vma, haddr); + } else { + entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); + entry = pte_mkspecial(entry); + } + pte = pte_offset_map(&_pmd, haddr); + VM_BUG_ON(!pte_none(*pte)); + set_pte_at(mm, haddr, pte, entry); + pte_unmap(pte); + } + smp_wmb(); /* make pte visible before pmd */ + pmd_populate(mm, pmd, pgtable); + spin_unlock(&mm->page_table_lock); + put_huge_zero_page(); + inc_mm_counter(mm, MM_ANONPAGES); + + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); + + ret |= VM_FAULT_WRITE; +out: + return ret; +out_free_page: + spin_unlock(&mm->page_table_lock); + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); + mem_cgroup_uncharge_page(page); + put_page(page); + goto out; +} + static int do_huge_pmd_wp_page_fallback(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, @@ -912,19 +1137,21 @@ int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, unsigned long address, pmd_t *pmd, pmd_t orig_pmd) { int ret = 0; - struct page *page, *new_page; + struct page *page = NULL, *new_page; unsigned long haddr; unsigned long mmun_start; /* For mmu_notifiers */ unsigned long mmun_end; /* For mmu_notifiers */ VM_BUG_ON(!vma->anon_vma); + haddr = address & HPAGE_PMD_MASK; + if (is_huge_zero_pmd(orig_pmd)) + goto alloc; spin_lock(&mm->page_table_lock); if (unlikely(!pmd_same(*pmd, orig_pmd))) goto out_unlock; page = pmd_page(orig_pmd); VM_BUG_ON(!PageCompound(page) || !PageHead(page)); - haddr = address & HPAGE_PMD_MASK; if (page_mapcount(page) == 1) { pmd_t entry; entry = pmd_mkyoung(orig_pmd); @@ -936,7 +1163,7 @@ int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, } get_page(page); spin_unlock(&mm->page_table_lock); - +alloc: if (transparent_hugepage_enabled(vma) && !transparent_hugepage_debug_cow()) new_page = alloc_hugepage_vma(transparent_hugepage_defrag(vma), @@ -946,24 +1173,34 @@ int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, if (unlikely(!new_page)) { count_vm_event(THP_FAULT_FALLBACK); - ret = do_huge_pmd_wp_page_fallback(mm, vma, address, - pmd, orig_pmd, page, haddr); - if (ret & VM_FAULT_OOM) - split_huge_page(page); - put_page(page); + if (is_huge_zero_pmd(orig_pmd)) { + ret = do_huge_pmd_wp_zero_page_fallback(mm, vma, + address, pmd, orig_pmd, haddr); + } else { + ret = do_huge_pmd_wp_page_fallback(mm, vma, address, + pmd, orig_pmd, page, haddr); + if (ret & VM_FAULT_OOM) + split_huge_page(page); + put_page(page); + } goto out; } count_vm_event(THP_FAULT_ALLOC); if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL))) { put_page(new_page); - split_huge_page(page); - put_page(page); + if (page) { + split_huge_page(page); + put_page(page); + } ret |= VM_FAULT_OOM; goto out; } - copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); + if (is_huge_zero_pmd(orig_pmd)) + clear_huge_page(new_page, haddr, HPAGE_PMD_NR); + else + copy_user_huge_page(new_page, page, haddr, vma, HPAGE_PMD_NR); __SetPageUptodate(new_page); mmun_start = haddr; @@ -971,7 +1208,8 @@ int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); spin_lock(&mm->page_table_lock); - put_page(page); + if (page) + put_page(page); if (unlikely(!pmd_same(*pmd, orig_pmd))) { spin_unlock(&mm->page_table_lock); mem_cgroup_uncharge_page(new_page); @@ -979,14 +1217,19 @@ int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma, goto out_mn; } else { pmd_t entry; - VM_BUG_ON(!PageHead(page)); entry = mk_huge_pmd(new_page, vma); pmdp_clear_flush(vma, haddr, pmd); page_add_new_anon_rmap(new_page, vma, haddr); set_pmd_at(mm, haddr, pmd, entry); update_mmu_cache_pmd(vma, address, pmd); - page_remove_rmap(page); - put_page(page); + if (is_huge_zero_pmd(orig_pmd)) { + add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR); + put_huge_zero_page(); + } else { + VM_BUG_ON(!PageHead(page)); + page_remove_rmap(page); + put_page(page); + } ret |= VM_FAULT_WRITE; } spin_unlock(&mm->page_table_lock); @@ -1055,15 +1298,21 @@ int zap_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma, pmd_t orig_pmd; pgtable = pgtable_trans_huge_withdraw(tlb->mm); orig_pmd = pmdp_get_and_clear(tlb->mm, addr, pmd); - page = pmd_page(orig_pmd); tlb_remove_pmd_tlb_entry(tlb, pmd, addr); - page_remove_rmap(page); - VM_BUG_ON(page_mapcount(page) < 0); - add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); - VM_BUG_ON(!PageHead(page)); - tlb->mm->nr_ptes--; - spin_unlock(&tlb->mm->page_table_lock); - tlb_remove_page(tlb, page); + if (is_huge_zero_pmd(orig_pmd)) { + tlb->mm->nr_ptes--; + spin_unlock(&tlb->mm->page_table_lock); + put_huge_zero_page(); + } else { + page = pmd_page(orig_pmd); + page_remove_rmap(page); + VM_BUG_ON(page_mapcount(page) < 0); + add_mm_counter(tlb->mm, MM_ANONPAGES, -HPAGE_PMD_NR); + VM_BUG_ON(!PageHead(page)); + tlb->mm->nr_ptes--; + spin_unlock(&tlb->mm->page_table_lock); + tlb_remove_page(tlb, page); + } pte_free(tlb->mm, pgtable); ret = 1; } @@ -1135,6 +1384,7 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, pmd_t entry; entry = pmdp_get_and_clear(mm, addr, pmd); entry = pmd_modify(entry, newprot); + BUG_ON(pmd_write(entry)); set_pmd_at(mm, addr, pmd, entry); spin_unlock(&vma->vm_mm->page_table_lock); ret = 1; @@ -1477,6 +1727,7 @@ int split_huge_page(struct page *page) struct anon_vma *anon_vma; int ret = 1; + BUG_ON(is_huge_zero_pfn(page_to_pfn(page))); BUG_ON(!PageAnon(page)); anon_vma = page_lock_anon_vma(page); if (!anon_vma) @@ -2336,19 +2587,65 @@ static int khugepaged(void *none) return 0; } -void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd) +static void __split_huge_zero_page_pmd(struct vm_area_struct *vma, + unsigned long haddr, pmd_t *pmd) +{ + struct mm_struct *mm = vma->vm_mm; + pgtable_t pgtable; + pmd_t _pmd; + int i; + + pmdp_clear_flush(vma, haddr, pmd); + /* leave pmd empty until pte is filled */ + + pgtable = pgtable_trans_huge_withdraw(mm); + pmd_populate(mm, &_pmd, pgtable); + + for (i = 0; i < HPAGE_PMD_NR; i++, haddr += PAGE_SIZE) { + pte_t *pte, entry; + entry = pfn_pte(my_zero_pfn(haddr), vma->vm_page_prot); + entry = pte_mkspecial(entry); + pte = pte_offset_map(&_pmd, haddr); + VM_BUG_ON(!pte_none(*pte)); + set_pte_at(mm, haddr, pte, entry); + pte_unmap(pte); + } + smp_wmb(); /* make pte visible before pmd */ + pmd_populate(mm, pmd, pgtable); + put_huge_zero_page(); +} + +void __split_huge_page_pmd(struct vm_area_struct *vma, unsigned long address, + pmd_t *pmd) { struct page *page; + struct mm_struct *mm = vma->vm_mm; + unsigned long haddr = address & HPAGE_PMD_MASK; + unsigned long mmun_start; /* For mmu_notifiers */ + unsigned long mmun_end; /* For mmu_notifiers */ + + BUG_ON(vma->vm_start > haddr || vma->vm_end < haddr + HPAGE_PMD_SIZE); + mmun_start = haddr; + mmun_end = haddr + HPAGE_PMD_SIZE; + mmu_notifier_invalidate_range_start(mm, mmun_start, mmun_end); spin_lock(&mm->page_table_lock); if (unlikely(!pmd_trans_huge(*pmd))) { spin_unlock(&mm->page_table_lock); + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); + return; + } + if (is_huge_zero_pmd(*pmd)) { + __split_huge_zero_page_pmd(vma, haddr, pmd); + spin_unlock(&mm->page_table_lock); + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); return; } page = pmd_page(*pmd); VM_BUG_ON(!page_count(page)); get_page(page); spin_unlock(&mm->page_table_lock); + mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end); split_huge_page(page); @@ -2356,6 +2653,16 @@ void __split_huge_page_pmd(struct mm_struct *mm, pmd_t *pmd) BUG_ON(pmd_trans_huge(*pmd)); } +void split_huge_page_pmd_mm(struct mm_struct *mm, unsigned long address, + pmd_t *pmd) +{ + struct vm_area_struct *vma; + + vma = find_vma(mm, address); + BUG_ON(vma == NULL); + split_huge_page_pmd(vma, address, pmd); +} + static void split_huge_page_address(struct mm_struct *mm, unsigned long address) { @@ -2370,7 +2677,7 @@ static void split_huge_page_address(struct mm_struct *mm, * Caller holds the mmap_sem write mode, so a huge pmd cannot * materialize from under us. */ - split_huge_page_pmd(mm, pmd); + split_huge_page_pmd_mm(mm, address, pmd); } void __vma_adjust_trans_huge(struct vm_area_struct *vma, |
