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Commit 13ece886 authored by Andrea Arcangeli's avatar Andrea Arcangeli Committed by Linus Torvalds
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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: default avatarAndrea Arcangeli <aarcange@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent ce83d217

mm/Kconfig

+25 −2
Original line number Diff line number Diff line
@@ -303,9 +303,8 @@ config NOMMU_INITIAL_TRIM_EXCESS 
	  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 @@ config TRANSPARENT_HUGEPAGE 


	  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

#

mm/huge_memory.c

+5 −0
Original line number Diff line number Diff line
@@ -27,7 +27,12 @@ 
 * allocations.

 */

unsigned long transparent_hugepage_flags __read_mostly =

#ifdef CONFIG_TRANSPARENT_HUGEPAGE_ALWAYS

	(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_KHUGEPAGED_FLAG);