tree 6e01667181bfc495b56e39748783ad2235a4f56e
parent c475a8ab625d567eacf5e30ec35d6d8704558062
author Abhijit Karmarkar <abhijitk@veritas.com> 1119399313 -0700
committer Linus Torvalds <torvalds@ppc970.osdl.org> 1119404781 -0700

[PATCH] msync: check pte dirty earlier

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>