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Commit 9ca24e2e authored by Vinayak Menon's avatar Vinayak Menon Committed by Linus Torvalds
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mmKconfig: add an option to disable bounce 



There are times when HIGHMEM is enabled, but we don't prefer
CONFIG_BOUNCE to be enabled.  CONFIG_BOUNCE can reduce the block device
throughput, and this is not ideal for machines where we don't gain much
by enabling it.  So provide an option to deselect CONFIG_BOUNCE.  The
observation was made while measuring eMMC throughput using iozone on an
ARM device with 1GB RAM.

Signed-off-by: default avatarVinayak Menon <vinayakm.list@gmail.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Randy Dunlap <rdunlap@infradead.org>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent b476e295

mm/Kconfig

+7 −1
Original line number Diff line number Diff line
@@ -263,8 +263,14 @@ config ZONE_DMA_FLAG 
	default "1"



config BOUNCE

	def_bool y

	bool "Enable bounce buffers"

	default y

	depends on BLOCK && MMU && (ZONE_DMA || HIGHMEM)

	help

	  Enable bounce buffers for devices that cannot access

	  the full range of memory available to the CPU. Enabled

	  by default when ZONE_DMA or HIGHMEM is selected, but you

	  may say n to override this.



# On the 'tile' arch, USB OHCI needs the bounce pool since tilegx will often

# have more than 4GB of memory, but we don't currently use the IOTLB to present