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Subject[PATCH v2 7/7] mm: Add config HUGE_IOMAP to enable huge I/O mappings
Add config HUGE_IOMAP to enable huge I/O mappings.  This feature
is set to Y by default when HAVE_ARCH_HUGE_VMAP is defined on the

Note that user can also disable this feature at boot-time by the
new kernel option "nohugeiomap" when necessary.

Signed-off-by: Toshi Kani <>
mm/Kconfig | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/mm/Kconfig b/mm/Kconfig
index 1d1ae6b..eb738ae 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -444,6 +444,17 @@ choice

+config HUGE_IOMAP
+ bool "Kernel huge I/O mapping support"
+ depends on HAVE_ARCH_HUGE_VMAP
+ default y
+ help
+ Kernel huge I/O mapping allows the kernel to transparently
+ create I/O mappings with huge pages for memory-mapped I/O
+ devices whenever possible. This feature can improve
+ performance of certain devices with large memory size, such
+ as NVM, and reduce the time to create their mappings.
# UP and nommu archs use km based percpu allocator

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