Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1356263

[PATCHv4 12/25] thp: skip file huge pmd on copy_huge_pmd()

Show all headers | View raw

copy_page_range() has a check for "Don't copy ptes where a page fault
will fill them correctly." It works on VMA level. We still copy all page
table entries from private mappings, even if they map page cache.

We can simplify copy_huge_pmd() a bit by skipping file PMDs.

We don't map file private pages with PMDs, so they only can map page
cache. It's safe to skip them as they can be re-faulted later.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 mm/huge_memory.c | 34 ++++++++++++++++------------------
 1 file changed, 16 insertions(+), 18 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 51c54d5a945b..0ef06d47bd24 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1082,14 +1082,15 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 	struct page *src_page;
 	pmd_t pmd;
 	pgtable_t pgtable = NULL;
-	int ret;
+	int ret = -ENOMEM;
 
-	if (!vma_is_dax(vma)) {
-		ret = -ENOMEM;
-		pgtable = pte_alloc_one(dst_mm, addr);
-		if (unlikely(!pgtable))
-			goto out;
-	}
+	/* Skip if can be re-fill on fault */
+	if (!vma_is_anonymous(vma))
+		return 0;
+
+	pgtable = pte_alloc_one(dst_mm, addr);
+	if (unlikely(!pgtable))
+		goto out;
 
 	dst_ptl = pmd_lock(dst_mm, dst_pmd);
 	src_ptl = pmd_lockptr(src_mm, src_pmd);
@@ -1097,7 +1098,7 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 
 	ret = -EAGAIN;
 	pmd = *src_pmd;
-	if (unlikely(!pmd_trans_huge(pmd) && !pmd_devmap(pmd))) {
+	if (unlikely(!pmd_trans_huge(pmd))) {
 		pte_free(dst_mm, pgtable);
 		goto out_unlock;
 	}
@@ -1120,16 +1121,13 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
 		goto out_unlock;
 	}
 
-	if (!vma_is_dax(vma)) {
-		/* thp accounting separate from pmd_devmap accounting */
-		src_page = pmd_page(pmd);
-		VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
-		get_page(src_page);
-		page_dup_rmap(src_page, true);
-		add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
-		atomic_long_inc(&dst_mm->nr_ptes);
-		pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
-	}
+	src_page = pmd_page(pmd);
+	VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
+	get_page(src_page);
+	page_dup_rmap(src_page, true);
+	add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
+	atomic_long_inc(&dst_mm->nr_ptes);
+	pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
 
 	pmdp_set_wrprotect(src_mm, addr, src_pmd);
 	pmd = pmd_mkold(pmd_wrprotect(pmd));
-- 
2.7.0

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCHv4 00/25] THP-enabled tmpfs/shmem "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-03-12 00:10 +0100
  [PATCHv4 13/25] thp: prepare change_huge_pmd() for file thp "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-03-12 00:10 +0100
  [PATCHv4 10/25] thp: handle file COW faults "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-03-12 00:10 +0100
  [PATCHv4 08/25] thp: support file pages in zap_huge_pmd() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-03-12 00:10 +0100
  [PATCHv4 12/25] thp: skip file huge pmd on copy_huge_pmd() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-03-12 00:10 +0100
  [PATCHv4 20/25] filemap: prepare find and delete operations for huge pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-03-12 00:10 +0100
  [PATCHv4 18/25] page-flags: relax policy for PG_mappedtodisk and PG_reclaim "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-03-12 00:10 +0100
  [PATCHv4 04/25] rmap: support file thp "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-03-12 00:10 +0100
  [PATCHv4 24/25] shmem: add huge pages support "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-03-12 00:10 +0100
  [PATCHv4 05/25] mm: introduce do_set_pmd() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-03-12 00:10 +0100
  [PATCHv4 19/25] radix-tree: implement radix_tree_maybe_preload_order() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-03-12 00:10 +0100
  [PATCHv4 23/25] shmem: get_unmapped_area align huge page "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-03-12 00:10 +0100
  [PATCHv4 22/25] shmem: prepare huge= mount option and sysfs knob "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-03-12 00:10 +0100
  [PATCHv4 21/25] truncate: handle file thp "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-03-12 00:10 +0100
  [PATCHv4 06/25] mm, rmap: account file thp pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-03-12 00:10 +0100
    [PATCHv5 06/25] mm, rmap: account file thp pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-03-15 16:40 +0100
  [PATCHv4 14/25] thp: run vma_adjust_trans_huge() outside i_mmap_rwsem "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-03-12 00:10 +0100
  [PATCHv4 07/25] thp, vmstats: add counters for huge file pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-03-12 00:10 +0100
  [PATCHv4 09/25] thp: handle file pages in split_huge_pmd() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-03-12 00:10 +0100
  [PATCHv5 26/25] thp: update Documentation/vm/transhuge.txt "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-03-15 17:00 +0100

csiph-web