From 5d6892407cab23d4bf2f6de065ca351a53849323 Mon Sep 17 00:00:00 2001 From: Andrea Arcangeli Date: Thu, 13 Jan 2011 15:47:07 -0800 Subject: thp: select CONFIG_COMPACTION if TRANSPARENT_HUGEPAGE enabled With transparent hugepage support we need compaction for the "defrag" sysfs controls to be effective. At the moment THP hangs the system if COMPACTION isn't selected, as without COMPACTION lumpy reclaim wouldn't be entirely disabled. So at the moment it's not orthogonal. When lumpy will be removed from the VM I can remove the select COMPACTION in theory, but then 99% of THP users would be still doing a mistake in disabling compaction, even if the mistake won't return in fatal runtime but just slightly degraded performance. So from a theoretical standpoing forcing the below select is not needed (the dependency isn't strict nor at compile time nor at runtime) but from a practical standpoint it is safer. If anybody really wants THP to run without compaction, it'd be such a weird setup that editing the Kconfig file to allow it will be surely not a problem. Signed-off-by: Andrea Arcangeli Acked-by: Mel Gorman Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/Kconfig | 1 + 1 file changed, 1 insertion(+) (limited to 'mm/Kconfig') diff --git a/mm/Kconfig b/mm/Kconfig index 3e81687263b5..3ad483bdf505 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -305,6 +305,7 @@ config NOMMU_INITIAL_TRIM_EXCESS config TRANSPARENT_HUGEPAGE bool "Transparent Hugepage Support" depends on X86 && MMU + select COMPACTION help Transparent Hugepages allows the kernel to use huge pages and huge tlb transparently to the applications whenever possible. -- cgit v1.2.3-59-g8ed1b