thp: transparent hugepage config choice
Allow to choose between the always|madvise default for page faults and
khugepaged at config time. madvise guarantees zero risk of higher memory
footprint for applications (applications using madvise(MADV_HUGEPAGE)
won't risk to use any more memory by backing their virtual regions with
hugepages).
Initially set the default to N and don't depend on EMBEDDED.
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/Kconfig b/mm/Kconfig
index d774f77..3e81687 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -303,9 +303,8 @@
See Documentation/nommu-mmap.txt for more information.
config TRANSPARENT_HUGEPAGE
- bool "Transparent Hugepage Support" if EMBEDDED
+ bool "Transparent Hugepage Support"
depends on X86 && MMU
- default y
help
Transparent Hugepages allows the kernel to use huge pages and
huge tlb transparently to the applications whenever possible.
@@ -316,6 +315,30 @@
If memory constrained on embedded, you may want to say N.
+choice
+ prompt "Transparent Hugepage Support sysfs defaults"
+ depends on TRANSPARENT_HUGEPAGE
+ default TRANSPARENT_HUGEPAGE_ALWAYS
+ help
+ Selects the sysfs defaults for Transparent Hugepage Support.
+
+ config TRANSPARENT_HUGEPAGE_ALWAYS
+ bool "always"
+ help
+ Enabling Transparent Hugepage always, can increase the
+ memory footprint of applications without a guaranteed
+ benefit but it will work automatically for all applications.
+
+ config TRANSPARENT_HUGEPAGE_MADVISE
+ bool "madvise"
+ help
+ Enabling Transparent Hugepage madvise, will only provide a
+ performance improvement benefit to the applications using
+ madvise(MADV_HUGEPAGE) but it won't risk to increase the
+ memory footprint of applications without a guaranteed
+ benefit.
+endchoice
+
#
# UP and nommu archs use km based percpu allocator
#