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. -- Kirill A. Shutemov -- 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>