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author | Nick Piggin <npiggin@suse.de> | 2009-01-06 14:38:55 -0800 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2009-01-06 15:58:58 -0800 |
commit | bf3f3bc5e734706730c12a323f9b2068052aa1f0 (patch) | |
tree | d93fb6beb0916cc10aeb5674578bfa3ac40371c9 /mm/shmem.c | |
parent | 3340289ddf29ca75c3acfb3a6b72f234b2f74d5c (diff) | |
download | op-kernel-dev-bf3f3bc5e734706730c12a323f9b2068052aa1f0.zip op-kernel-dev-bf3f3bc5e734706730c12a323f9b2068052aa1f0.tar.gz |
mm: don't mark_page_accessed in fault path
Doing a mark_page_accessed at fault-time, then doing SetPageReferenced at
unmap-time if the pte is young has a number of problems.
mark_page_accessed is supposed to be roughly the equivalent of a young pte
for unmapped references. Unfortunately it doesn't come with any context:
after being called, reclaim doesn't know who or why the page was touched.
So calling mark_page_accessed not only adds extra lru or PG_referenced
manipulations for pages that are already going to have pte_young ptes anyway,
but it also adds these references which are difficult to work with from the
context of vma specific references (eg. MADV_SEQUENTIAL pte_young may not
wish to contribute to the page being referenced).
Then, simply doing SetPageReferenced when zapping a pte and finding it is
young, is not a really good solution either. SetPageReferenced does not
correctly promote the page to the active list for example. So after removing
mark_page_accessed from the fault path, several mmap()+touch+munmap() would
have a very different result from several read(2) calls for example, which
is not really desirable.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Johannes Weiner <hannes@saeurebad.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/shmem.c')
0 files changed, 0 insertions, 0 deletions