Commit c164e038 authored by Kirill A. Shutemov's avatar Kirill A. Shutemov Committed by Linus Torvalds
Browse files

mm: fix huge zero page accounting in smaps report 



As a small zero page, huge zero page should not be accounted in smaps
report as normal page.

For small pages we rely on vm_normal_page() to filter out zero page, but
vm_normal_page() is not designed to handle pmds.  We only get here due
hackish cast pmd to pte in smaps_pte_range() -- pte and pmd format is not
necessary compatible on each and every architecture.

Let's add separate codepath to handle pmds.  follow_trans_huge_pmd() will
detect huge zero page for us.

We would need pmd_dirty() helper to do this properly.  The patch adds it
to THP-enabled architectures which don't yet have one.

[akpm@linux-foundation.org: use do_div to fix 32-bit build]
Signed-off-by: default avatar"Kirill A. Shutemov" <kirill@shutemov.name>
Reported-by: default avatarFengguang Wu <fengguang.wu@intel.com>
Tested-by: default avatarFengwei Yin <yfw.kernel@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 2314b42d

arch/arm64/include/asm/pgtable.h

+1 −0
Original line number Diff line number Diff line
@@ -279,6 +279,7 @@ void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address, 
#endif /* CONFIG_HAVE_RCU_TABLE_FREE */

#endif /* CONFIG_TRANSPARENT_HUGEPAGE */



#define pmd_dirty(pmd)		pte_dirty(pmd_pte(pmd))

#define pmd_young(pmd)		pte_young(pmd_pte(pmd))

#define pmd_wrprotect(pmd)	pte_pmd(pte_wrprotect(pmd_pte(pmd)))

#define pmd_mksplitting(pmd)	pte_pmd(pte_mkspecial(pmd_pte(pmd)))

arch/powerpc/include/asm/pgtable-ppc64.h

+1 −0
Original line number Diff line number Diff line
@@ -467,6 +467,7 @@ static inline pte_t *pmdp_ptep(pmd_t *pmd) 
}



#define pmd_pfn(pmd)		pte_pfn(pmd_pte(pmd))

#define pmd_dirty(pmd)		pte_dirty(pmd_pte(pmd))

#define pmd_young(pmd)		pte_young(pmd_pte(pmd))

#define pmd_mkold(pmd)		pte_pmd(pte_mkold(pmd_pte(pmd)))

#define pmd_wrprotect(pmd)	pte_pmd(pte_wrprotect(pmd_pte(pmd)))

arch/sparc/include/asm/pgtable_64.h

+7 −0
Original line number Diff line number Diff line
@@ -667,6 +667,13 @@ static inline unsigned long pmd_pfn(pmd_t pmd) 
}



#ifdef CONFIG_TRANSPARENT_HUGEPAGE

static inline unsigned long pmd_dirty(pmd_t pmd)

{

	pte_t pte = __pte(pmd_val(pmd));



	return pte_dirty(pte);

}



static inline unsigned long pmd_young(pmd_t pmd)

{

	pte_t pte = __pte(pmd_val(pmd));

arch/x86/include/asm/pgtable.h

+5 −0
Original line number Diff line number Diff line
@@ -99,6 +99,11 @@ static inline int pte_young(pte_t pte) 
	return pte_flags(pte) & _PAGE_ACCESSED;

}



static inline int pmd_dirty(pmd_t pmd)

{

	return pmd_flags(pmd) & _PAGE_DIRTY;

}



static inline int pmd_young(pmd_t pmd)

{

	return pmd_flags(pmd) & _PAGE_ACCESSED;

fs/proc/task_mmu.c

+68 −36
Original line number Diff line number Diff line
@@ -447,58 +447,91 @@ struct mem_size_stats { 
	u64 pss;

};



static void smaps_account(struct mem_size_stats *mss, struct page *page,

		unsigned long size, bool young, bool dirty)

{

	int mapcount;



	if (PageAnon(page))

		mss->anonymous += size;



	mss->resident += size;

	/* Accumulate the size in pages that have been accessed. */

	if (young || PageReferenced(page))

		mss->referenced += size;

	mapcount = page_mapcount(page);

	if (mapcount >= 2) {

		u64 pss_delta;



		if (dirty || PageDirty(page))

			mss->shared_dirty += size;

		else

			mss->shared_clean += size;

		pss_delta = (u64)size << PSS_SHIFT;

		do_div(pss_delta, mapcount);

		mss->pss += pss_delta;

	} else {

		if (dirty || PageDirty(page))

			mss->private_dirty += size;

		else

			mss->private_clean += size;

		mss->pss += (u64)size << PSS_SHIFT;

	}

}



static void smaps_pte_entry(pte_t ptent, unsigned long addr,

		unsigned long ptent_size, struct mm_walk *walk)

static void smaps_pte_entry(pte_t *pte, unsigned long addr,

		struct mm_walk *walk)

{

	struct mem_size_stats *mss = walk->private;

	struct vm_area_struct *vma = mss->vma;

	pgoff_t pgoff = linear_page_index(vma, addr);

	struct page *page = NULL;

	int mapcount;



	if (pte_present(ptent)) {

		page = vm_normal_page(vma, addr, ptent);

	} else if (is_swap_pte(ptent)) {

		swp_entry_t swpent = pte_to_swp_entry(ptent);

	if (pte_present(*pte)) {

		page = vm_normal_page(vma, addr, *pte);

	} else if (is_swap_pte(*pte)) {

		swp_entry_t swpent = pte_to_swp_entry(*pte);



		if (!non_swap_entry(swpent))

			mss->swap += ptent_size;

			mss->swap += PAGE_SIZE;

		else if (is_migration_entry(swpent))

			page = migration_entry_to_page(swpent);

	} else if (pte_file(ptent)) {

		if (pte_to_pgoff(ptent) != pgoff)

			mss->nonlinear += ptent_size;

	} else if (pte_file(*pte)) {

		if (pte_to_pgoff(*pte) != pgoff)

			mss->nonlinear += PAGE_SIZE;

	}



	if (!page)

		return;



	if (PageAnon(page))

		mss->anonymous += ptent_size;



	if (page->index != pgoff)

		mss->nonlinear += ptent_size;

		mss->nonlinear += PAGE_SIZE;



	mss->resident += ptent_size;

	/* Accumulate the size in pages that have been accessed. */

	if (pte_young(ptent) || PageReferenced(page))

		mss->referenced += ptent_size;

	mapcount = page_mapcount(page);

	if (mapcount >= 2) {

		if (pte_dirty(ptent) || PageDirty(page))

			mss->shared_dirty += ptent_size;

		else

			mss->shared_clean += ptent_size;

		mss->pss += (ptent_size << PSS_SHIFT) / mapcount;

	} else {

		if (pte_dirty(ptent) || PageDirty(page))

			mss->private_dirty += ptent_size;

		else

			mss->private_clean += ptent_size;

		mss->pss += (ptent_size << PSS_SHIFT);

	smaps_account(mss, page, PAGE_SIZE, pte_young(*pte), pte_dirty(*pte));

}



#ifdef CONFIG_TRANSPARENT_HUGEPAGE

static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,

		struct mm_walk *walk)

{

	struct mem_size_stats *mss = walk->private;

	struct vm_area_struct *vma = mss->vma;

	struct page *page;



	/* FOLL_DUMP will return -EFAULT on huge zero page */

	page = follow_trans_huge_pmd(vma, addr, pmd, FOLL_DUMP);

	if (IS_ERR_OR_NULL(page))

		return;

	mss->anonymous_thp += HPAGE_PMD_SIZE;

	smaps_account(mss, page, HPAGE_PMD_SIZE,

			pmd_young(*pmd), pmd_dirty(*pmd));

}

#else

static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,

		struct mm_walk *walk)

{

}

#endif



static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,

			   struct mm_walk *walk)
@@ -509,9 +542,8 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, 
	spinlock_t *ptl;



	if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {

		smaps_pte_entry(*(pte_t *)pmd, addr, HPAGE_PMD_SIZE, walk);

		smaps_pmd_entry(pmd, addr, walk);

		spin_unlock(ptl);

		mss->anonymous_thp += HPAGE_PMD_SIZE;

		return 0;

	}
@@ -524,7 +556,7 @@ static int smaps_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, 
	 */

	pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);

	for (; addr != end; pte++, addr += PAGE_SIZE)

		smaps_pte_entry(*pte, addr, PAGE_SIZE, walk);

		smaps_pte_entry(pte, addr, walk);

	pte_unmap_unlock(pte - 1, ptl);

	cond_resched();

	return 0;

CRA Git | Maintained and supported by SUSTech CRA and CCSE