thp: introduce sysfs knob to disable huge zero page (79da5407) · Commits · 戴 / test

Documentation/vm/transhuge.txt

+7 −0

Original line number	Diff line number	Diff line
		@@ -116,6 +116,13 @@ echo always >/sys/kernel/mm/transparent_hugepage/defrag
		echo madvise >/sys/kernel/mm/transparent_hugepage/defrag
		echo never >/sys/kernel/mm/transparent_hugepage/defrag

		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

		khugepaged will be automatically started when
		transparent_hugepage/enabled is set to "always" or "madvise, and it'll
		be automatically shutdown if it's set to "never".

include/linux/huge_mm.h

+4 −0

Original line number	Diff line number	Diff line
		@@ -39,6 +39,7 @@ enum transparent_hugepage_flag {
		TRANSPARENT_HUGEPAGE_DEFRAG_FLAG,
		TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG,
		TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG,
		TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG,
		#ifdef CONFIG_DEBUG_VM
		TRANSPARENT_HUGEPAGE_DEBUG_COW_FLAG,
		#endif
		@@ -78,6 +79,9 @@ extern bool is_vma_temporary_stack(struct vm_area_struct *vma);
		(transparent_hugepage_flags & \
		(1<<TRANSPARENT_HUGEPAGE_DEFRAG_REQ_MADV_FLAG) && \
		(__vma)->vm_flags & VM_HUGEPAGE))
		#define transparent_hugepage_use_zero_page() \
		(transparent_hugepage_flags & \
		(1<<TRANSPARENT_HUGEPAGE_USE_ZERO_PAGE_FLAG))
		#ifdef CONFIG_DEBUG_VM
		#define transparent_hugepage_debug_cow() \
		(transparent_hugepage_flags & \

mm/huge_memory.c

+19 −2

Original line number	Diff line number	Diff line
		@@ -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 8512 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);

Admin message