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SubjectRe: [PATCHv5 23/28] thp: add option to setup migration entiries during PMD split
On 04/23/2015 11:03 PM, Kirill A. Shutemov wrote:
> We are going to use migration PTE entires to stabilize page counts.
> If the page is mapped with PMDs we need to split the PMD and setup
> migration enties. It's reasonable to combine these operations to avoid
> double-scanning over the page table.
>
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
> Tested-by: Sasha Levin <sasha.levin@oracle.com>

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
> mm/huge_memory.c | 23 +++++++++++++++--------
> 1 file changed, 15 insertions(+), 8 deletions(-)
>
> diff --git a/mm/huge_memory.c b/mm/huge_memory.c
> index 5885ef8f0fad..2f9e2e882bab 100644
> --- a/mm/huge_memory.c
> +++ b/mm/huge_memory.c
> @@ -23,6 +23,7 @@
> #include <linux/pagemap.h>
> #include <linux/migrate.h>
> #include <linux/hashtable.h>
> +#include <linux/swapops.h>
>
> #include <asm/tlb.h>
> #include <asm/pgalloc.h>
> @@ -2551,7 +2552,7 @@ static void __split_huge_zero_page_pmd(struct vm_area_struct *vma,
> }
>
> static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
> - unsigned long haddr)
> + unsigned long haddr, bool freeze)
> {
> struct mm_struct *mm = vma->vm_mm;
> struct page *page;
> @@ -2593,12 +2594,18 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
> * transferred to avoid any possibility of altering
> * permissions across VMAs.
> */
> - entry = mk_pte(page + i, vma->vm_page_prot);
> - entry = maybe_mkwrite(pte_mkdirty(entry), vma);
> - if (!write)
> - entry = pte_wrprotect(entry);
> - if (!young)
> - entry = pte_mkold(entry);
> + if (freeze) {
> + swp_entry_t swp_entry;
> + swp_entry = make_migration_entry(page + i, write);
> + entry = swp_entry_to_pte(swp_entry);
> + } else {
> + entry = mk_pte(page + i, vma->vm_page_prot);
> + entry = maybe_mkwrite(pte_mkdirty(entry), vma);
> + if (!write)
> + entry = pte_wrprotect(entry);
> + if (!young)
> + entry = pte_mkold(entry);
> + }
> pte = pte_offset_map(&_pmd, haddr);
> BUG_ON(!pte_none(*pte));
> set_pte_at(mm, haddr, pte, entry);
> @@ -2625,7 +2632,7 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
> mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
> ptl = pmd_lock(mm, pmd);
> if (likely(pmd_trans_huge(*pmd)))
> - __split_huge_pmd_locked(vma, pmd, haddr);
> + __split_huge_pmd_locked(vma, pmd, haddr, false);
> spin_unlock(ptl);
> mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
> }
>



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