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

Groups > linux.kernel > #1372922

[PATCHv6 01/30] thp, mlock: update unevictable-lru.txt

Show all headers | View raw

Add description of THP handling into unevictable-lru.txt.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 Documentation/vm/unevictable-lru.txt | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/Documentation/vm/unevictable-lru.txt b/Documentation/vm/unevictable-lru.txt
index fa3b527086fa..0026a8d33fc0 100644
--- a/Documentation/vm/unevictable-lru.txt
+++ b/Documentation/vm/unevictable-lru.txt
@@ -461,6 +461,27 @@ unevictable LRU is enabled, the work of compaction is mostly handled by
 the page migration code and the same work flow as described in MIGRATING
 MLOCKED PAGES will apply.
 
+MLOCKING TRANSPARENT HUGE PAGES
+-------------------------------
+
+A transparent huge page is represented by a single entry on an LRU list.
+Therefore, we can only make unevictable an entire compound page, not
+individual subpages.
+
+If a user tries to mlock() part of a huge page, we want the rest of the
+page to be reclaimable.
+
+We cannot just split the page on partial mlock() as split_huge_page() can
+fail and new intermittent failure mode for the syscall is undesirable.
+
+We handle this by keeping PTE-mapped huge pages on normal LRU lists: the
+PMD on border of VM_LOCKED VMA will be split into PTE table.
+
+This way the huge page is accessible for vmscan. Under memory pressure the
+page will be split, subpages which belong to VM_LOCKED VMAs will be moved
+to unevictable LRU and the rest can be reclaimed.
+
+See also comment in follow_trans_huge_pmd().
 
 mmap(MAP_LOCKED) SYSTEM CALL HANDLING
 -------------------------------------
-- 
2.8.0.rc3

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

Thread

[PATCHv6 00/30] THP-enabled tmpfs/shmem using compound pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-04-07 01:00 +0200
  [PATCHv6 11/30] thp: handle file pages in mremap() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-04-07 01:00 +0200
  [PATCHv6 17/30] vmscan: split file huge pages before paging them out "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-04-07 01:00 +0200
  [PATCHv6 06/30] mm: introduce do_set_pmd() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-04-07 01:00 +0200
  [PATCHv6 14/30] thp: run vma_adjust_trans_huge() outside i_mmap_rwsem "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-04-07 01:00 +0200
  [PATCHv6 10/30] thp: handle file COW faults "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-04-07 01:00 +0200
  [PATCHv6 22/30] mm, rmap: account shmem thp pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-04-07 01:00 +0200
  [PATCHv6 26/30] shmem, thp: respect MADV_{NO,}HUGEPAGE for file mappings "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-04-07 01:00 +0200
  [PATCHv6 15/30] thp: file pages support for split_huge_page() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-04-07 01:00 +0200
  [PATCHv6 01/30] thp, mlock: update unevictable-lru.txt "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-04-07 01:00 +0200
  [PATCHv6 18/30] page-flags: relax policy for PG_mappedtodisk and PG_reclaim "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-04-07 01:00 +0200
  [PATCHv6 05/30] rmap: support file thp "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-04-07 01:00 +0200
  [PATCHv6 08/30] thp: support file pages in zap_huge_pmd() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-04-07 01:00 +0200
  [PATCHv6 12/30] thp: skip file huge pmd on copy_huge_pmd() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-04-07 01:00 +0200
  [PATCHv6 13/30] thp: prepare change_huge_pmd() for file thp "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-04-07 01:00 +0200
  [PATCHv6 21/30] truncate: handle file thp "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-04-07 01:00 +0200
  [PATCHv6 07/30] thp, vmstats: add counters for huge file pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-04-07 01:00 +0200
  [PATCHv6 20/30] filemap: prepare find and delete operations for huge pages "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-04-07 01:00 +0200
  [PATCHv6 23/30] shmem: prepare huge= mount option and sysfs knob "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-04-07 01:00 +0200
  [PATCHv6 19/30] radix-tree: implement radix_tree_maybe_preload_order() "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-04-07 01:00 +0200
  [PATCHv6 04/30] mm: postpone page table allocation until we have page to map "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-04-07 01:10 +0200
  [PATCHv6 02/30] mm: do not pass mm_struct into handle_mm_fault "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2016-04-07 01:10 +0200

csiph-web