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authorHeiko Carstens <heiko.carstens@de.ibm.com>2012-01-12 17:17:27 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2012-01-12 20:13:03 -0800
commit43570fd2f47ba518145e9289f54cde3dba4c8b25 (patch)
tree67aa61c8b972f4b3af66cd89082222e77e06a4cb /arch/Kconfig
parent0d259cf8190b9c446eefd5225ffcc3941e76a432 (diff)
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mm,slub,x86: decouple size of struct page from CONFIG_CMPXCHG_LOCAL
While implementing cmpxchg_double() on s390 I realized that we don't set CONFIG_CMPXCHG_LOCAL despite the fact that we have support for it. However setting that option will increase the size of struct page by eight bytes on 64 bit, which we certainly do not want. Also, it doesn't make sense that a present cpu feature should increase the size of struct page. Besides that it looks like the dependency to CMPXCHG_LOCAL is wrong and that it should depend on CMPXCHG_DOUBLE instead. This patch: If an architecture supports CMPXCHG_LOCAL this shouldn't result automatically in larger struct pages if the SLUB allocator is used. Instead introduce a new config option "HAVE_ALIGNED_STRUCT_PAGE" which can be selected if a double word aligned struct page is required. Also update x86 Kconfig so that it should work as before. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Acked-by: Christoph Lameter <cl@linux.com> Cc: Pekka Enberg <penberg@kernel.org> Cc: Ingo Molnar <mingo@elte.hu> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'arch/Kconfig')
-rw-r--r--arch/Kconfig8
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/Kconfig b/arch/Kconfig
index 2505740b81d..a2c5c077c32 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -185,4 +185,12 @@ config HAVE_RCU_TABLE_FREE
config ARCH_HAVE_NMI_SAFE_CMPXCHG
bool
+config HAVE_ALIGNED_STRUCT_PAGE
+ bool
+ help
+ This makes sure that struct pages are double word aligned and that
+ e.g. the SLUB allocator can perform double word atomic operations
+ on a struct page for better performance. However selecting this
+ might increase the size of a struct page by a word.
+
source "kernel/gcov/Kconfig"