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authorEric B Munson <emunson@akamai.com>2015-04-15 16:13:23 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2015-04-15 16:35:17 -0700
commit922c0551a795dccadeb1dadc756d93fe3e303180 (patch)
treec02ccd2b3df1c2fc0068dbe3677fc92baab85616
parent5bbe3547aa3ba5242366a322a28996872301b703 (diff)
downloadlinux-922c0551a795dccadeb1dadc756d93fe3e303180.tar.bz2
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. [akpm@linux-foundation.org: identify /proc/sys/vm/compact_unevictable directly] Signed-off-by: Eric B Munson <emunson@akamai.com> Cc: Michal Hocko <mhocko@suse.cz> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Christoph Lameter <cl@linux.com> Cc: David Rientjes <rientjes@google.com> Cc: Rik van Riel <riel@redhat.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Mel Gorman <mgorman@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--Documentation/vm/unevictable-lru.txt12
1 files changed, 12 insertions, 0 deletions
diff --git a/Documentation/vm/unevictable-lru.txt b/Documentation/vm/unevictable-lru.txt
index 86cb4624fc5a..3be0bfc4738d 100644
--- a/Documentation/vm/unevictable-lru.txt
+++ b/Documentation/vm/unevictable-lru.txt
@@ -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.
+COMPACTING MLOCKED PAGES
+------------------------
+
+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.
+
+
mmap(MAP_LOCKED) SYSTEM CALL HANDLING
-------------------------------------