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 diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 648fca4..0eb801a 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 diff --git a/arch/x86/mm/init_32.c b/arch/x86/mm/init_32.c index 2cde0a34..29f7c6d9 100644 --- a/arch/x86/mm/init_32.c +++ b/arch/x86/mm/init_32.c @@ -678,8 +678,10 @@ static void __init zone_sizes_init(void) { unsigned long max_zone_pfns[MAX_NR_ZONES]; memset(max_zone_pfns, 0, sizeof(max_zone_pfns)); +#ifdef CONFIG_ZONE_DMA max_zone_pfns[ZONE_DMA] = virt_to_phys((char *)MAX_DMA_ADDRESS) >> PAGE_SHIFT; +#endif max_zone_pfns[ZONE_NORMAL] = max_low_pfn; #ifdef CONFIG_HIGHMEM max_zone_pfns[ZONE_HIGHMEM] = highend_pfn; diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index 0404bb3..d865c4a 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -616,7 +616,9 @@ void __init paging_init(void) unsigned long max_zone_pfns[MAX_NR_ZONES]; memset(max_zone_pfns, 0, sizeof(max_zone_pfns)); +#ifdef CONFIG_ZONE_DMA max_zone_pfns[ZONE_DMA] = MAX_DMA_PFN; +#endif max_zone_pfns[ZONE_DMA32] = MAX_DMA32_PFN; max_zone_pfns[ZONE_NORMAL] = max_pfn; -- cgit v0.10.2