mm: more likely reclaim MADV_SEQUENTIAL mappings

File pages mapped only in sequentially read mappings are perfect reclaim
canditates.

This patch makes these mappings behave like weak references, their pages
will be reclaimed unless they have a strong reference from a normal
mapping as well.

It changes the reclaim and the unmap path where they check if the page has
been referenced.  In both cases, accesses through sequentially read
mappings will be ignored.

Benchmark results from KOSAKI Motohiro:

    http://marc.info/?l=linux-mm&m=122485301925098&w=2

Signed-off-by: Johannes Weiner <hannes@saeurebad.de>
Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/mm/memory.c b/mm/memory.c
index 5e0e91cc6b67..99e8d5c7b312 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -767,7 +767,8 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
                         else {
                                 if (pte_dirty(ptent))
                                         set_page_dirty(page);
-                                if (pte_young(ptent))
+                                if (pte_young(ptent) &&
+                                    likely(!VM_SequentialReadHint(vma)))
                                         mark_page_accessed(page);
                                 file_rss--;
                         }