On Fri, Apr 04, 2014 at 11:57:14AM +0530, Madhavan Srinivasan wrote:
> Kirill A. Shutemov with faultaround patchset introduced
> vm_ops->map_pages() for mapping easy accessible pages around
> fault address in hope to reduce number of minor page faults.
>
> This patch creates infrastructure to move the FAULT_AROUND_ORDER
> to arch/ using Kconfig. This will enable architecture maintainers
> to decide on suitable FAULT_AROUND_ORDER value based on
> performance data for that architecture. Patch also adds
> FAULT_AROUND_ORDER Kconfig element in arch/X86.
>
> Signed-off-by: Madhavan Srinivasan <maddy@xxxxxxxxxxxxxxxxxx>
> ---
> arch/x86/Kconfig | 4 ++++
> include/linux/mm.h | 9 +++++++++
> mm/memory.c | 12 +++++-------
> 3 files changed, 18 insertions(+), 7 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 9c0a657..5833f22 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1177,6 +1177,10 @@ config DIRECT_GBPAGES
> support it. This can improve the kernel's performance a tiny bit by
> reducing TLB pressure. If in doubt, say "Y".
>
> +config FAULT_AROUND_ORDER
> + int
> + default "4"
> +
> # Common NUMA Features
> config NUMA
> bool "Numa Memory Allocation and Scheduler Support"
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 0bd4359..b93c1c3 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -26,6 +26,15 @@ struct file_ra_state;
> struct user_struct;
> struct writeback_control;
>
> +/*
> + * 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 CONFIG_FAULT_AROUND_ORDER
> +#define CONFIG_FAULT_AROUND_ORDER 0
> +#endif
> +
I don't think it should be in header file: nobody except mm/memory.c cares.
Just put it instead '#define FAULT_AROUND_ORDER'.
> #ifndef CONFIG_NEED_MULTIPLE_NODES /* Don't use mapnrs, do it properly */
> extern unsigned long max_mapnr;
>
> diff --git a/mm/memory.c b/mm/memory.c
> index b02c584..22a4a89 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3358,10 +3358,8 @@ 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;
> +static unsigned int fault_around_order = CONFIG_FAULT_AROUND_ORDER;
>
> static int fault_around_order_get(void *data, u64 *val)
> {
> @@ -3371,7 +3369,7 @@ static int fault_around_order_get(void *data, u64 *val)
>
> static int fault_around_order_set(void *data, u64 val)
> {
> - BUILD_BUG_ON((1UL << FAULT_AROUND_ORDER) > PTRS_PER_PTE);
> + BUILD_BUG_ON((1UL << CONFIG_FAULT_AROUND_ORDER) > PTRS_PER_PTE);
> if (1UL << val > PTRS_PER_PTE)
> return -EINVAL;
> fault_around_order = val;
> @@ -3406,14 +3404,14 @@ static inline unsigned long fault_around_pages(void)
> {
> unsigned long nr_pages;
>
> - nr_pages = 1UL << FAULT_AROUND_ORDER;
> + nr_pages = 1UL << CONFIG_FAULT_AROUND_ORDER;
> BUILD_BUG_ON(nr_pages > PTRS_PER_PTE);
> return nr_pages;
> }
>
> static inline unsigned long fault_around_mask(void)
> {
> - return ~((1UL << (PAGE_SHIFT + FAULT_AROUND_ORDER)) - 1);
> + return ~((1UL << (PAGE_SHIFT + CONFIG_FAULT_AROUND_ORDER)) - 1);
> }
> #endif
>
> @@ -3471,7 +3469,7 @@ static int do_read_fault(struct mm_struct *mm, struct vm_area_struct *vma,
> * if page by the offset is not ready to be mapped (cold cache or
> * something).
> */
> - if (vma->vm_ops->map_pages) {
> + if ((vma->vm_ops->map_pages) && (fault_around_pages() > 1)) {
if (vma->vm_ops->map_pages && fault_around_pages()) {
> pte = pte_offset_map_lock(mm, pmd, address, &ptl);
> do_fault_around(vma, address, pte, pgoff, flags);
> if (!pte_same(*pte, orig_pte))
> --
> 1.7.10.4
>
> --
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--
Kirill A. Shutemov
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