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Groups > linux.kernel > #1157917

[PATCHv6 30/36] thp: add option to setup migration entiries during PMD split

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We are going to use migration PTE entires to stabilize page counts.
If the page is mapped with PMDs we need to split the PMD and setup
migration enties. It's reasonable to combine these operations to avoid
double-scanning over the page table.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Tested-by: Sasha Levin <sasha.levin@oracle.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
---
 mm/huge_memory.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 0f1f5731a893..aa852094c7b9 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -24,6 +24,7 @@
 #include <linux/migrate.h>
 #include <linux/hashtable.h>
 #include <linux/userfaultfd_k.h>
+#include <linux/swapops.h>
 
 #include <asm/tlb.h>
 #include <asm/pgalloc.h>
@@ -2576,7 +2577,7 @@ static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
 }
 
 static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
-		unsigned long haddr)
+		unsigned long haddr, bool freeze)
 {
 	struct mm_struct *mm = vma->vm_mm;
 	struct page *page;
@@ -2614,12 +2615,18 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
 		 * transferred to avoid any possibility of altering
 		 * permissions across VMAs.
 		 */
-		entry = mk_pte(page + i, vma->vm_page_prot);
-		entry = maybe_mkwrite(pte_mkdirty(entry), vma);
-		if (!write)
-			entry = pte_wrprotect(entry);
-		if (!young)
-			entry = pte_mkold(entry);
+		if (freeze) {
+			swp_entry_t swp_entry;
+			swp_entry = make_migration_entry(page + i, write);
+			entry = swp_entry_to_pte(swp_entry);
+		} else {
+			entry = mk_pte(page + i, vma->vm_page_prot);
+			entry = maybe_mkwrite(pte_mkdirty(entry), vma);
+			if (!write)
+				entry = pte_wrprotect(entry);
+			if (!young)
+				entry = pte_mkold(entry);
+		}
 		pte = pte_offset_map(&_pmd, haddr);
 		BUG_ON(!pte_none(*pte));
 		set_pte_at(mm, haddr, pte, entry);
@@ -2661,7 +2668,7 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
 	mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
 	ptl = pmd_lock(mm, pmd);
 	if (likely(pmd_trans_huge(*pmd)))
-		__split_huge_pmd_locked(vma, pmd, haddr);
+		__split_huge_pmd_locked(vma, pmd, haddr, false);
 	spin_unlock(ptl);
 	mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
 }
-- 
2.1.4

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Thread

[PATCHv6 00/36] THP refcounting redesign "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:10 +0200
  [PATCHv6 12/36] thp: drop all split_huge_page()-related code "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:10 +0200
  [PATCHv6 18/36] arm, thp: remove infrastructure for handling splitting PMDs "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:10 +0200
  [PATCHv6 01/36] mm, proc: adjust PSS calculation "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:10 +0200
  [PATCHv6 28/36] mm, numa: skip PTE-mapped THP on numa fault "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:10 +0200
  [PATCHv6 02/36] rmap: add argument to charge compound page "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:10 +0200
  [PATCHv6 24/36] x86, thp: remove infrastructure for handling splitting PMDs "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:20 +0200
  [PATCHv6 08/36] khugepaged: ignore pmd tables with THP mapped with ptes "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:20 +0200
  [PATCHv6 19/36] mips, thp: remove infrastructure for handling splitting PMDs "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:20 +0200
  [PATCHv6 33/36] migrate_pages: try to split pages on qeueuing "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:20 +0200
  [PATCHv6 13/36] mm: drop tail page refcounting "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:20 +0200
  [PATCHv6 27/36] mm: differentiate page_mapped() from page_mapcount() for compound pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:20 +0200
  [PATCHv6 32/36] thp: reintroduce split_huge_page() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:20 +0200
  [PATCHv6 21/36] s390, thp: remove infrastructure for handling splitting PMDs "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:20 +0200
  [PATCHv6 29/36] thp: implement split_huge_pmd() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:20 +0200
  [PATCHv6 20/36] powerpc, thp: remove infrastructure for handling splitting PMDs "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:20 +0200
  [PATCHv6 17/36] arm64, thp: remove infrastructure for handling splitting PMDs "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:20 +0200
  [PATCHv6 34/36] thp: introduce deferred_split_huge_page() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:20 +0200
  [PATCHv6 30/36] thp: add option to setup migration entiries during PMD split "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:20 +0200
  [PATCHv6 10/36] mm, vmstats: new THP splitting event "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:20 +0200
  [PATCHv6 23/36] tile, thp: remove infrastructure for handling splitting PMDs "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:20 +0200
  [PATCHv6 06/36] mm: handle PTE-mapped tail pages in gerneric fast gup implementaiton "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:20 +0200
  [PATCHv6 31/36] thp, mm: split_huge_page(): caller need to lock page "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:20 +0200
  [PATCHv6 35/36] mm: re-enable THP "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:20 +0200
  [PATCHv6 16/36] mm, thp: remove compound_lock "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2015-06-03 19:20 +0200

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