Messages in this thread Patch in this message | | | From | Peter Zijlstra <> | Date | Sat, 24 Jun 2006 00:31:44 +0200 | Subject | [PATCH 4/5] mm: optimize the new mprotect() code a bit |
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From: Peter Zijlstra <a.p.zijlstra@chello.nl>
mprotect() resets the page protections, which could result in extra write faults for those pages whose dirty state we track using write faults and are dirty already.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> --- mm/mprotect.c | 33 +++++++++++++++++++++++---------- 1 file changed, 23 insertions(+), 10 deletions(-)
Index: 2.6-mm/mm/mprotect.c =================================================================== --- 2.6-mm.orig/mm/mprotect.c 2006-06-23 01:35:24.000000000 +0200 +++ 2.6-mm/mm/mprotect.c 2006-06-23 15:06:10.000000000 +0200 @@ -28,7 +28,8 @@ #include <asm/tlbflush.h> static void change_pte_range(struct mm_struct *mm, pmd_t *pmd, - unsigned long addr, unsigned long end, pgprot_t newprot) + unsigned long addr, unsigned long end, pgprot_t newprot, + int dirty_accountable) { pte_t *pte, oldpte; spinlock_t *ptl; @@ -43,7 +44,14 @@ static void change_pte_range(struct mm_s * bits by wiping the pte and then setting the new pte * into place. */ - ptent = pte_modify(ptep_get_and_clear(mm, addr, pte), newprot); + ptent = ptep_get_and_clear(mm, addr, pte); + ptent = pte_modify(ptent, newprot); + /* + * Avoid taking write faults for pages we know to be + * dirty. + */ + if (dirty_accountable && pte_dirty(ptent)) + ptent = pte_mkwrite(ptent); set_pte_at(mm, addr, pte, ptent); lazy_mmu_prot_update(ptent); #ifdef CONFIG_MIGRATION @@ -67,7 +75,8 @@ static void change_pte_range(struct mm_s } static inline void change_pmd_range(struct mm_struct *mm, pud_t *pud, - unsigned long addr, unsigned long end, pgprot_t newprot) + unsigned long addr, unsigned long end, pgprot_t newprot, + int dirty_accountable) { pmd_t *pmd; unsigned long next; @@ -77,12 +86,13 @@ static inline void change_pmd_range(stru next = pmd_addr_end(addr, end); if (pmd_none_or_clear_bad(pmd)) continue; - change_pte_range(mm, pmd, addr, next, newprot); + change_pte_range(mm, pmd, addr, next, newprot, dirty_accountable); } while (pmd++, addr = next, addr != end); } static inline void change_pud_range(struct mm_struct *mm, pgd_t *pgd, - unsigned long addr, unsigned long end, pgprot_t newprot) + unsigned long addr, unsigned long end, pgprot_t newprot, + int dirty_accountable) { pud_t *pud; unsigned long next; @@ -92,12 +102,13 @@ static inline void change_pud_range(stru next = pud_addr_end(addr, end); if (pud_none_or_clear_bad(pud)) continue; - change_pmd_range(mm, pud, addr, next, newprot); + change_pmd_range(mm, pud, addr, next, newprot, dirty_accountable); } while (pud++, addr = next, addr != end); } static void change_protection(struct vm_area_struct *vma, - unsigned long addr, unsigned long end, pgprot_t newprot) + unsigned long addr, unsigned long end, pgprot_t newprot, + int dirty_accountable) { struct mm_struct *mm = vma->vm_mm; pgd_t *pgd; @@ -111,7 +122,7 @@ static void change_protection(struct vm_ next = pgd_addr_end(addr, end); if (pgd_none_or_clear_bad(pgd)) continue; - change_pud_range(mm, pgd, addr, next, newprot); + change_pud_range(mm, pgd, addr, next, newprot, dirty_accountable); } while (pgd++, addr = next, addr != end); flush_tlb_range(vma, start, end); } @@ -128,6 +139,7 @@ mprotect_fixup(struct vm_area_struct *vm pgprot_t newprot; pgoff_t pgoff; int error; + int dirty_accountable = 0; if (newflags == oldflags) { *pprev = vma; @@ -190,8 +202,10 @@ success: (VM_WRITE|VM_SHARED)) && vma->vm_file && vma->vm_file->f_mapping && mapping_cap_account_dirty(vma->vm_file->f_mapping)) || - (vma->vm_ops && vma->vm_ops->page_mkwrite)) + (vma->vm_ops && vma->vm_ops->page_mkwrite)) { mask &= ~VM_SHARED; + dirty_accountable = 1; + } newprot = protection_map[newflags & mask]; @@ -204,7 +218,7 @@ success: if (is_vm_hugetlb_page(vma)) hugetlb_change_protection(vma, start, end, newprot); else - change_protection(vma, start, end, newprot); + change_protection(vma, start, end, newprot, dirty_accountable); vm_stat_account(mm, oldflags, vma->vm_file, -nrpages); vm_stat_account(mm, newflags, vma->vm_file, nrpages); return 0; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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