From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Date: Tue, 27 Jun 2006 20:28:53 +0200 Message-Id: <20060627182853.20891.28744.sendpatchset@lappy> In-Reply-To: <20060627182801.20891.11456.sendpatchset@lappy> References: <20060627182801.20891.11456.sendpatchset@lappy> Subject: [PATCH 4/5] mm: optimize the new mprotect() code a bit Sender: owner-linux-mm@kvack.org Return-Path: To: linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Hugh Dickins , Andrew Morton , David Howells , Peter Zijlstra , Christoph Lameter , Martin Bligh , Nick Piggin , Linus Torvalds List-ID: From: Peter Zijlstra 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 --- mm/mprotect.c | 31 ++++++++++++++++++++++--------- 1 file changed, 22 insertions(+), 9 deletions(-) Index: linux-2.6-dirty/mm/mprotect.c =================================================================== --- linux-2.6-dirty.orig/mm/mprotect.c 2006-06-27 13:26:19.000000000 +0200 +++ linux-2.6-dirty/mm/mprotect.c 2006-06-27 13:28:49.000000000 +0200 @@ -27,7 +27,8 @@ #include 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; @@ -42,7 +43,14 @@ 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 @@ -66,7 +74,8 @@ 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; @@ -76,12 +85,13 @@ 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; @@ -91,12 +101,13 @@ 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; @@ -110,7 +121,7 @@ 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); } @@ -126,6 +137,7 @@ mprotect_fixup(struct vm_area_struct *vm unsigned long mask = VM_READ|VM_WRITE|VM_EXEC|VM_SHARED; pgoff_t pgoff; int error; + int dirty_accountable = 0; if (newflags == oldflags) { *pprev = vma; @@ -180,14 +192,16 @@ success: * held in write mode. */ vma->vm_flags = newflags; - if (vma_wants_writenotify(vma, VM_NOTIFY_NO_PROT)) + if (vma_wants_writenotify(vma, VM_NOTIFY_NO_PROT)) { mask &= ~VM_SHARED; + dirty_accountable = 1; + } vma->vm_page_prot = protection_map[newflags & mask]; if (is_vm_hugetlb_page(vma)) hugetlb_change_protection(vma, start, end, vma->vm_page_prot); else - change_protection(vma, start, end, vma->vm_page_prot); + change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable); vm_stat_account(mm, oldflags, vma->vm_file, -nrpages); vm_stat_account(mm, newflags, vma->vm_file, nrpages); return 0; -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org