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authorKirill A. Shutemov <kirill.shutemov@linux.intel.com>2012-12-12 13:51:12 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2012-12-12 17:38:32 -0800
commit79da5407eeadc740fbf4b45d6df7d7f8e6adaf2c (patch)
treea9f1ca92b2711bb84a4707c904fcada24614d60e /mm/huge_memory.c
parentd8a8e1f0da3d29d7268b3300c96a059d63901b76 (diff)
thp: introduce sysfs knob to disable huge zero page
By default kernel tries to use huge zero page on read page fault. It's possible to disable huge zero page by writing 0 or enable it back by writing 1: echo 0 >/sys/kernel/mm/transparent_hugepage/khugepaged/use_zero_page echo 1 >/sys/kernel/mm/transparent_hugepage/khugepaged/use_zero_page Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Andi Kleen <ak@linux.intel.com> Cc: "H. Peter Anvin" <hpa@linux.intel.com> Cc: Mel Gorman <mel@csn.ul.ie> Cc: David Rientjes <rientjes@google.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/huge_memory.c')
-rw-r--r--mm/huge_memory.c21
1 files changed, 19 insertions, 2 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 9a5d45dfad4..72835cea0b0 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -39,7 +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;
@@ -357,6 +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)
@@ -378,6 +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
@@ -779,7 +795,8 @@ 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;
unsigned long zero_pfn;
pgtable = pte_alloc_one(mm, haddr);