Commit 922c0551 authored by Eric B Munson's avatar Eric B Munson Committed by Linus Torvalds

Documentation/vm/unevictable-lru.txt: document interaction between compaction...

Documentation/vm/unevictable-lru.txt: document interaction between compaction and the unevictable LRU

The memory compaction code uses the migration code to do most of the
work in compaction.  However, the compaction code interacts with the
unevictable LRU differently than migration code and this difference
should be noted in the documentation.

[ identify /proc/sys/vm/compact_unevictable directly]
Signed-off-by: default avatarEric B Munson <>
Cc: Michal Hocko <>
Cc: Vlastimil Babka <>
Cc: Christoph Lameter <>
Cc: David Rientjes <>
Cc: Rik van Riel <>
Cc: Thomas Gleixner <>
Cc: Peter Zijlstra <>
Cc: Mel Gorman <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 5bbe3547
......@@ -22,6 +22,7 @@ CONTENTS
- Filtering special vmas.
- munlock()/munlockall() system call handling.
- Migrating mlocked pages.
- Compacting mlocked pages.
- mmap(MAP_LOCKED) system call handling.
- munmap()/exit()/exec() system call handling.
- try_to_unmap().
......@@ -450,6 +451,17 @@ list because of a race between munlock and migration, page migration uses the
putback_lru_page() function to add migrated pages back to the LRU.
The unevictable LRU can be scanned for compactable regions and the default
behavior is to do so. /proc/sys/vm/compact_unevictable_allowed controls
this behavior (see Documentation/sysctl/vm.txt). Once scanning of the
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.
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