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| author | David Rientjes <rientjes@google.com> | 2011-05-16 13:54:10 -0700 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2011-05-16 14:03:28 -0700 |
| commit | dc382fd5bcca7098a984705ed6ac880f539d068e (patch) | |
| tree | c1e3cba89fcb91092061fecd5a2d688335e30216 | |
| parent | e5a10c1bd12a5d71bbb6406c1b0dbbc9d8958397 (diff) | |
| download | linux-stable-dc382fd5bcca7098a984705ed6ac880f539d068e.tar.gz linux-stable-dc382fd5bcca7098a984705ed6ac880f539d068e.tar.bz2 linux-stable-dc382fd5bcca7098a984705ed6ac880f539d068e.zip | |
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 <rientjes@google.com>
Link: http://lkml.kernel.org/r/alpine.DEB.2.00.1105161353560.4353@chino.kir.corp.google.com
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
| -rw-r--r-- | arch/x86/Kconfig | 9 | ||||
| -rw-r--r-- | arch/x86/mm/init_32.c | 2 | ||||
| -rw-r--r-- | arch/x86/mm/init_64.c | 2 |
3 files changed, 12 insertions, 1 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 648fca42ae6a..0eb801a75dee 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 2cde0a34bed6..29f7c6d98179 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 0404bb3a077e..d865c4aeec55 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; |