From 922c0551a795dccadeb1dadc756d93fe3e303180 Mon Sep 17 00:00:00 2001 From: Eric B Munson Date: Wed, 15 Apr 2015 16:13:23 -0700 Subject: [PATCH] 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 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: Andrew Morton Signed-off-by: Linus Torvalds --- Documentation/vm/unevictable-lru.txt | 12 ++++++++++++ 1 file changed, 12 insertions(+) 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 ------------------------------------- -- GitLab