Kirill A. Shutemov with the commit 96bacfe542 introduced vm_ops->map_pages() for mapping easy accessible pages around fault address in hope to reduce number of minor page faults. Based on his workload runs, suggested FAULT_AROUND_ORDER (knob to control the numbers of pages to map) is 4. This patch moves the FAULT_AROUND_ORDER macro to arch/ for architecture maintainers to decide on suitable FAULT_AROUND_ORDER value based on performance data for that architecture. Signed-off-by: Madhavan Srinivasan <maddy@xxxxxxxxxxxxxxxxxx> --- arch/powerpc/include/asm/pgtable.h | 6 ++++++ arch/x86/include/asm/pgtable.h | 5 +++++ include/asm-generic/pgtable.h | 10 ++++++++++ mm/memory.c | 2 -- 4 files changed, 21 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/include/asm/pgtable.h b/arch/powerpc/include/asm/pgtable.h index 3ebb188..9fcbd48 100644 --- a/arch/powerpc/include/asm/pgtable.h +++ b/arch/powerpc/include/asm/pgtable.h @@ -19,6 +19,12 @@ struct mm_struct; #endif /* + * With a few real world workloads that were run, + * the performance data showed that a value of 3 is more advantageous. + */ +#define FAULT_AROUND_ORDER 3 + +/* * We save the slot number & secondary bit in the second half of the * PTE page. We use the 8 bytes per each pte entry. */ diff --git a/arch/x86/include/asm/pgtable.h b/arch/x86/include/asm/pgtable.h index 938ef1d..8387a65 100644 --- a/arch/x86/include/asm/pgtable.h +++ b/arch/x86/include/asm/pgtable.h @@ -7,6 +7,11 @@ #include <asm/pgtable_types.h> /* + * Based on Kirill's test results, fault around order is set to 4 + */ +#define FAULT_AROUND_ORDER 4 + +/* * Macro to mark a page protection value as UC- */ #define pgprot_noncached(prot) \ diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h index 1ec08c1..62f7f07 100644 --- a/include/asm-generic/pgtable.h +++ b/include/asm-generic/pgtable.h @@ -7,6 +7,16 @@ #include <linux/mm_types.h> #include <linux/bug.h> + +/* + * Fault around order is a control knob to decide the fault around pages. + * Default value is set to 0UL (disabled), but the arch can override it as + * desired. + */ +#ifndef FAULT_AROUND_ORDER +#define FAULT_AROUND_ORDER 0UL +#endif + /* * On almost all architectures and configurations, 0 can be used as the * upper ceiling to free_pgtables(): on many architectures it has the same diff --git a/mm/memory.c b/mm/memory.c index b02c584..fd79ffc 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3358,8 +3358,6 @@ void do_set_pte(struct vm_area_struct *vma, unsigned long address, update_mmu_cache(vma, address, pte); } -#define FAULT_AROUND_ORDER 4 - #ifdef CONFIG_DEBUG_FS static unsigned int fault_around_order = FAULT_AROUND_ORDER; -- 1.7.10.4 -- 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>