#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"
(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;
/* during fragmentation poll the hugepage allocator once every minute */
static unsigned int khugepaged_alloc_sleep_millisecs __read_mostly = 60000;
static struct task_struct *khugepaged_thread __read_mostly;
-static unsigned long huge_zero_pfn __read_mostly;
static DEFINE_MUTEX(khugepaged_mutex);
static DEFINE_SPINLOCK(khugepaged_mm_lock);
static DECLARE_WAIT_QUEUE_HEAD(khugepaged_wait);
return err;
}
-static int init_huge_zero_pfn(void)
+static atomic_t huge_zero_refcount;
+static unsigned long huge_zero_pfn __read_mostly;
+
+static inline bool is_huge_zero_pfn(unsigned long pfn)
{
- struct page *hpage;
- unsigned long pfn;
+ unsigned long zero_pfn = ACCESS_ONCE(huge_zero_pfn);
+ return zero_pfn && pfn == zero_pfn;
+}
- hpage = alloc_pages((GFP_TRANSHUGE | __GFP_ZERO) & ~__GFP_MOVABLE,
+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 (!hpage)
- return -ENOMEM;
- pfn = page_to_pfn(hpage);
- if (cmpxchg(&huge_zero_pfn, 0, pfn))
- __free_page(hpage);
- return 0;
+ 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 inline bool is_huge_zero_pfn(unsigned long pfn)
+static void put_huge_zero_page(void)
{
- return huge_zero_pfn && pfn == huge_zero_pfn;
+ /*
+ * Counter should never go to zero here. Only shrinker can put
+ * last reference.
+ */
+ BUG_ON(atomic_dec_and_test(&huge_zero_refcount));
}
-static inline bool is_huge_zero_pmd(pmd_t pmd)
+static int shrink_huge_zero_page(struct shrinker *shrink,
+ struct shrink_control *sc)
{
- return is_huge_zero_pfn(pmd_pfn(pmd));
+ 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,
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)
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
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
}
#endif
-static void set_huge_zero_page(pgtable_t pgtable, struct mm_struct *mm,
- struct vm_area_struct *vma, unsigned long haddr, pmd_t *pmd)
+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;
- entry = pfn_pmd(huge_zero_pfn, vma->vm_page_prot);
+ 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,
return VM_FAULT_OOM;
if (unlikely(khugepaged_enter(vma)))
return VM_FAULT_OOM;
- if (!(flags & FAULT_FLAG_WRITE)) {
+ if (!(flags & FAULT_FLAG_WRITE) &&
+ transparent_hugepage_use_zero_page()) {
pgtable_t pgtable;
- if (unlikely(!huge_zero_pfn && init_huge_zero_pfn())) {
- count_vm_event(THP_FAULT_FALLBACK);
- goto out;
- }
+ 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_huge_zero_page(pgtable, mm, vma, haddr, pmd);
+ 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),
* a page table.
*/
if (is_huge_zero_pmd(pmd)) {
- set_huge_zero_page(pgtable, dst_mm, vma, addr, dst_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;
}
static int do_huge_pmd_wp_zero_page_fallback(struct mm_struct *mm,
struct vm_area_struct *vma, unsigned long address,
- pmd_t *pmd, unsigned long haddr)
+ pmd_t *pmd, pmd_t orig_pmd, unsigned long haddr)
{
pgtable_t pgtable;
pmd_t _pmd;
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 */
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,
count_vm_event(THP_FAULT_FALLBACK);
if (is_huge_zero_pmd(orig_pmd)) {
ret = do_huge_pmd_wp_zero_page_fallback(mm, vma,
- address, pmd, haddr);
+ address, pmd, orig_pmd, haddr);
} else {
ret = do_huge_pmd_wp_page_fallback(mm, vma, address,
pmd, orig_pmd, page, haddr);
page_add_new_anon_rmap(new_page, vma, haddr);
set_pmd_at(mm, haddr, pmd, entry);
update_mmu_cache_pmd(vma, address, pmd);
- if (is_huge_zero_pmd(orig_pmd))
+ if (is_huge_zero_pmd(orig_pmd)) {
add_mm_counter(mm, MM_ANONPAGES, HPAGE_PMD_NR);
- else {
+ put_huge_zero_page();
+ } else {
VM_BUG_ON(!PageHead(page));
page_remove_rmap(page);
put_page(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);
}
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,
projects / karo-tx-linux.git / blobdiff