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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: Vinayak 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: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Vinayak Menon 2013-04-29 15:08:55 -07:00 committed by Linus Torvalds
parent b476e2951f
commit 9ca24e2e19
1 changed files with 7 additions and 1 deletions
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8
mm/Kconfig
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@ -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