From dc382fd5bcca7098a984705ed6ac880f539d068e Mon Sep 17 00:00:00 2001 From: David Rientjes Date: Mon, 16 May 2011 13:54:10 -0700 Subject: x86, mm: Allow ZONE_DMA to be configurable ZONE_DMA is unnecessary for a large number of machines that do not require less than 32-bit DMA addressing, e.g. ISA legacy DMA or PCI cards with a restricted DMA address mask. This patch allows users to disable ZONE_DMA for x86 if they know they will not be using such devices with their kernel. This prevents the VM from unnecessarily reserving a ratio of memory (defaulting to 1/256th of system capacity) with lowmem_reserve_ratio for such allocations when it will never be used. Signed-off-by: David Rientjes Link: http://lkml.kernel.org/r/alpine.DEB.2.00.1105161353560.4353@chino.kir.corp.google.com Signed-off-by: H. Peter Anvin --- arch/x86/Kconfig | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) (limited to 'arch/x86/Kconfig') diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 648fca42ae6..0eb801a75de 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -112,7 +112,14 @@ config MMU def_bool y config ZONE_DMA - def_bool y + bool "DMA memory allocation support" if EXPERT + default y + help + DMA memory allocation support allows devices with less than 32-bit + addressing to allocate within the first 16MB of address space. + Disable if no such devices will be used. + + If unsure, say Y. config SBUS bool -- cgit v1.2.3-18-g5258