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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>
This commit is contained in:
Andrea Arcangeli 2011-01-13 15:47:07 -08:00 committed by Linus Torvalds
parent ce83d2174e
commit 13ece886d9
2 changed files with 30 additions and 2 deletions
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27
mm/Kconfig
View File

@ -303,9 +303,8 @@ config NOMMU_INITIAL_TRIM_EXCESS
See Documentation/nommu-mmap.txt for more information. See Documentation/nommu-mmap.txt for more information.
config TRANSPARENT_HUGEPAGE config TRANSPARENT_HUGEPAGE
bool "Transparent Hugepage Support" if EMBEDDED bool "Transparent Hugepage Support"
depends on X86 && MMU depends on X86 && MMU
default y
help help
Transparent Hugepages allows the kernel to use huge pages and Transparent Hugepages allows the kernel to use huge pages and
huge tlb transparently to the applications whenever possible. huge tlb transparently to the applications whenever possible.
@ -316,6 +315,30 @@ config TRANSPARENT_HUGEPAGE
If memory constrained on embedded, you may want to say N. 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 # UP and nommu archs use km based percpu allocator
# #

5
mm/huge_memory.c
View File

@ -27,7 +27,12 @@
* allocations. * allocations.
*/ */
unsigned long transparent_hugepage_flags __read_mostly = unsigned long transparent_hugepage_flags __read_mostly =
#ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS
(1<<TRANSPARENT_HUGEPAGE_FLAG)| (1<<TRANSPARENT_HUGEPAGE_FLAG)|
#endif
#ifdef CONFIG_TRANSPARENT_HUGEPAGE_MADVISE
(1<<TRANSPARENT_HUGEPAGE_REQ_MADV_FLAG)|
#endif
(1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)| (1<<TRANSPARENT_HUGEPAGE_DEFRAG_FLAG)|
(1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG); (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG);