From b32eaf71db6085f2ba54cf3ddf688bfc858219d0 Mon Sep 17 00:00:00 2001 From: Michal Hocko Date: Thu, 25 Aug 2016 15:17:05 -0700 Subject: [PATCH] mm: clarify COMPACTION Kconfig text The current wording of the COMPACTION Kconfig help text doesn't emphasise that disabling COMPACTION might cripple the page allocator which relies on the compaction quite heavily for high order requests and an unexpected OOM can happen with the lack of compaction. Make sure we are vocal about that. Link: http://lkml.kernel.org/r/20160823091726.GK23577@dhcp22.suse.cz Signed-off-by: Michal Hocko Cc: Markus Trippelsdorf Cc: Mel Gorman Cc: Joonsoo Kim Cc: Vlastimil Babka Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/Kconfig | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/mm/Kconfig b/mm/Kconfig index 78a23c5c302d..be0ee11fa0d9 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -262,7 +262,14 @@ config COMPACTION select MIGRATION depends on MMU help - Allows the compaction of memory for the allocation of huge pages. + Compaction is the only memory management component to form + high order (larger physically contiguous) memory blocks + reliably. The page allocator relies on compaction heavily and + the lack of the feature can lead to unexpected OOM killer + invocations for high order memory requests. You shouldn't + disable this option unless there really is a strong reason for + it and then we would be really interested to hear about that at + linux-mm@kvack.org. # # support for page migration -- 2.20.1