From 43570fd2f47ba518145e9289f54cde3dba4c8b25 Mon Sep 17 00:00:00 2001 From: Heiko Carstens Date: Thu, 12 Jan 2012 17:17:27 -0800 Subject: 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 Acked-by: Christoph Lameter Cc: Pekka Enberg Cc: Ingo Molnar Cc: Thomas Gleixner Cc: "H. Peter Anvin" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/Kconfig | 8 ++++++++ 1 file changed, 8 insertions(+) (limited to 'arch/Kconfig') diff --git a/arch/Kconfig b/arch/Kconfig index 2505740b81d2..a2c5c077c32d 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" -- cgit v1.2.3-55-g7522