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[PATCH] msync: check pte dirty earlier

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It's common practice to msync a large address range regularly, in which
often only a few ptes have actually been dirtied since the previous pass.

sync_pte_range then goes much faster if it tests whether pte is dirty
before locating and accessing each struct page cacheline; and it is hardly
slowed by ptep_clear_flush_dirty repeating that test in the opposite case,
when every pte actually is dirty.

But beware, s390's pte_dirty always says false, since its dirty bit is kept
in the storage key, located via the struct page address.  So skip this
optimization in its case: use a pte_maybe_dirty macro which just says true
if page_test_and_clear_dirty is implemented.

Signed-off-by: Abhijit Karmarkar <abhijitk@veritas.com>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Abhijit Karmarkar 2005-06-21 17:15:13 -07:00 committed by Linus Torvalds
parent c475a8ab62
commit b4955ce3dd
2 changed files with 5 additions and 0 deletions
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3
include/asm-generic/pgtable.h
View file

@ -125,6 +125,9 @@ static inline void ptep_set_wrprotect(struct mm_struct *mm, unsigned long addres
#ifndef __HAVE_ARCH_PAGE_TEST_AND_CLEAR_DIRTY
#define page_test_and_clear_dirty(page) (0)
#define pte_maybe_dirty(pte) pte_dirty(pte)
#else
#define pte_maybe_dirty(pte) (1)
#endif
#ifndef __HAVE_ARCH_PAGE_TEST_AND_CLEAR_YOUNG

2
mm/msync.c
View file

@ -34,6 +34,8 @@ static void sync_pte_range(struct vm_area_struct *vma, pmd_t *pmd,
if (!pte_present(*pte))
continue;
if (!pte_maybe_dirty(*pte))
continue;
pfn = pte_pfn(*pte);
if (!pfn_valid(pfn))
continue;