From: Vinayak Menon <vinayakm.l...@gmail.com>
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.l...@gmail.com>
---
mm/Kconfig | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/mm/Kconfig b/mm/Kconfig
index 3bea74f..29f9736 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -263,8 +263,14 @@ config ZONE_DMA_FLAG
default "1"
config BOUNCE
+ bool "Enable bounce buffers"
def_bool 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 HIGMEM 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
--
1.7.10.4
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