Xen cannot use automatic NUMA balancing as they are depending on the same PTE bit. There is another software bit that is currently used by software dirty tracking of pages. This patch allows Xen to use that bit for automatic NUMA balancing if MEM_SOFT_DIRTY is not enabled. If KMEMCHECK is enabled then the bit is only set on global page tables so there should be no collision with NUMA_BALANCING. This shuffling can be disabled if/when Xen moves away from using _PAGE_BIT_IOMAP. Signed-off-by: Mel Gorman <mgorman@xxxxxxx> --- arch/x86/Kconfig | 2 +- arch/x86/include/asm/pgtable_types.h | 14 +++++++++++++- 2 files changed, 14 insertions(+), 2 deletions(-) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 4fab25a..3c4ba81 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -26,7 +26,7 @@ config X86 select ARCH_MIGHT_HAVE_PC_SERIO select HAVE_AOUT if X86_32 select HAVE_UNSTABLE_SCHED_CLOCK - select ARCH_SUPPORTS_NUMA_BALANCING if X86_64 && !XEN + select ARCH_SUPPORTS_NUMA_BALANCING if X86_64 && (!XEN || !MEM_SOFT_DIRTY) select ARCH_SUPPORTS_INT128 if X86_64 select ARCH_WANTS_PROT_NUMA_PROT_NONE select HAVE_IDE diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h index 49b3e15..fa84d1f 100644 --- a/arch/x86/include/asm/pgtable_types.h +++ b/arch/x86/include/asm/pgtable_types.h @@ -24,11 +24,23 @@ #define _PAGE_BIT_CPA_TEST _PAGE_BIT_SOFTW1 #define _PAGE_BIT_SPLITTING _PAGE_BIT_SOFTW1 /* only valid on a PSE pmd */ #define _PAGE_BIT_IOMAP _PAGE_BIT_SOFTW2 /* flag used to indicate IO mapping */ -#define _PAGE_BIT_NUMA _PAGE_BIT_SOFTW2 /* for NUMA balancing hinting */ #define _PAGE_BIT_HIDDEN _PAGE_BIT_SOFTW3 /* hidden by kmemcheck */ #define _PAGE_BIT_SOFT_DIRTY _PAGE_BIT_SOFTW3 /* software dirty tracking */ #define _PAGE_BIT_NX 63 /* No execute: only valid after cpuid check */ +/* + * Automatic NUMA balancing uses _PAGE_BIT_SOFTW2 if available as generally it + * is only used on the kernel page tables and is easily shared. Unfortunately, + * Xen also uses this bit so on those configurations it is necessary to use + * _PAGE_BIT_SOFTW3 but then MEM_SOFT_DIRTY cannot be enabled at the same time + * as it also requires that bit. Constraint is enforced by Kconfig. + */ +#ifndef CONFIG_XEN +#define _PAGE_BIT_NUMA _PAGE_BIT_SOFTW2 +#else +#define _PAGE_BIT_NUMA _PAGE_BIT_SOFTW3 +#endif + /* If _PAGE_BIT_PRESENT is clear, we use these: */ /* - if the user mapped it with PROT_NONE; pte_present gives true */ #define _PAGE_BIT_PROTNONE _PAGE_BIT_GLOBAL -- 1.8.4.5 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>