The patch titled
Subject: thp, mlock: update unevictable-lru.txt
has been removed from the -mm tree. Its filename was
thp-mlock-update-unevictable-lrutxt.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
Subject: thp, mlock: update unevictable-lru.txt
Add description of THP handling into unevictable-lru.txt.
Link: http://lkml.kernel.org/r/1466021202-61880-7-git-send-email-kirill.shutemov@xxxxxxxxxxxxxxx
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/vm/unevictable-lru.txt | 21 +++++++++++++++++++++
1 file changed, 21 insertions(+)
diff -puN Documentation/vm/unevictable-lru.txt~thp-mlock-update-unevictable-lrutxt Documentation/vm/unevictable-lru.txt
--- a/Documentation/vm/unevictable-lru.txt~thp-mlock-update-unevictable-lrutxt
+++ a/Documentation/vm/unevictable-lru.txt
@@ -461,6 +461,27 @@ unevictable LRU is enabled, the work of
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
-------------------------------------
_
Patches currently in -mm which might be from kirill.shutemov@xxxxxxxxxxxxxxx are
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