This makes CMA memory area size zero for x86 in default configuration (doesn't change on the other architectures). If default CMA size is zero, DMA_CMA is disabled. It can be enabled by passing cma= to the kernel.
This makes less impact on x86. Because there is no mainline driver that requires it for x86, and Peter Hurley reported the performance regression, as this is trying to drive _all_ dma mapping allocations through a _very_ small window. Signed-off-by: Akinobu Mita <[email protected]> Reported-by: Peter Hurley <[email protected]> Cc: Peter Hurley <[email protected]> Cc: Chuck Ebbert <[email protected]> Cc: Marek Szyprowski <[email protected]> Cc: Konrad Rzeszutek Wilk <[email protected]> Cc: David Woodhouse <[email protected]> Cc: Don Dutile <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Ingo Molnar <[email protected]> Cc: "H. Peter Anvin" <[email protected]> Cc: Andi Kleen <[email protected]> Cc: Yinghai Lu <[email protected]> Cc: [email protected] Cc: [email protected] --- drivers/base/Kconfig | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/base/Kconfig b/drivers/base/Kconfig index 4e7f0ff..92a5987e 100644 --- a/drivers/base/Kconfig +++ b/drivers/base/Kconfig @@ -240,6 +240,7 @@ comment "Default contiguous memory area size:" config CMA_SIZE_MBYTES int "Size in Mega Bytes" depends on !CMA_SIZE_SEL_PERCENTAGE + default 0 if X86 default 16 help Defines the size (in MiB) of the default memory area for Contiguous @@ -248,6 +249,7 @@ config CMA_SIZE_MBYTES config CMA_SIZE_PERCENTAGE int "Percentage of total memory" depends on !CMA_SIZE_SEL_MBYTES + default 0 if X86 default 10 help Defines the size of the default memory area for Contiguous Memory -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
