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authorPeter Zijlstra <a.p.zijlstra@chello.nl>2006-09-25 23:30:59 -0700
committerLinus Torvalds <torvalds@g5.osdl.org>2006-09-26 08:48:44 -0700
commitc1e6098b23bb46e2b488fe9a26f831f867157483 (patch)
tree6bac4d3cfaab3e7153a15d1a24f9211b2de37ba6 /mm/mprotect.c
parentedc79b2a46ed854595e40edcf3f8b37f9f14aa3f (diff)
downloadvexpress-lsk-c1e6098b23bb46e2b488fe9a26f831f867157483.tar.gz
[PATCH] mm: optimize the new mprotect() code a bit
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> Cc: Hugh Dickins <hugh@veritas.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'mm/mprotect.c')
-rw-r--r--mm/mprotect.c34
1 files changed, 24 insertions, 10 deletions
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 367b7f6c063..955f9d0e38a 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -27,7 +27,8 @@
#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;
@@ -42,7 +43,14 @@ static void change_pte_range(struct mm_struct *mm, pmd_t *pmd,
* 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_struct *mm, pmd_t *pmd,
}
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(struct mm_struct *mm, pud_t *pud,
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(struct mm_struct *mm, pgd_t *pgd,
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_area_struct *vma,
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);
}
@@ -125,6 +136,7 @@ mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
unsigned long charged = 0;
pgoff_t pgoff;
int error;
+ int dirty_accountable = 0;
if (newflags == oldflags) {
*pprev = vma;
@@ -181,14 +193,16 @@ success:
vma->vm_flags = newflags;
vma->vm_page_prot = protection_map[newflags &
(VM_READ|VM_WRITE|VM_EXEC|VM_SHARED)];
- if (vma_wants_writenotify(vma))
+ if (vma_wants_writenotify(vma)) {
vma->vm_page_prot = protection_map[newflags &
(VM_READ|VM_WRITE|VM_EXEC)];
+ dirty_accountable = 1;
+ }
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;