From: Vinayak Menon <vinayakm.list@xxxxxxxxx> 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@xxxxxxxxx> --- mm/Kconfig | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff --git a/mm/Kconfig b/mm/Kconfig index 3bea74f..e742d06 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -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 -- 1.7.10.4 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>