On Tuesday 25 March 2014 11:06 PM, Kirill A. Shutemov wrote: > On Tue, Mar 25, 2014 at 12:20:15PM +0530, Madhavan Srinivasan wrote: >> 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 > > FAULT_AROUND_ORDER == 0 case should be handled separately in > do_read_fault(): no reason to go to do_fault_around() if we are going to > fault in only one page. > ok agreed. I am thinking of adding FAULT_AROUND_ORDER check with map_pages check in the do_read_fault. Kindly share your thoughts. With regards Maddy -- 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>