From bf3f3bc5e734706730c12a323f9b2068052aa1f0 Mon Sep 17 00:00:00 2001 From: Nick Piggin Date: Tue, 6 Jan 2009 14:38:55 -0800 Subject: 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 Acked-by: Johannes Weiner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memory.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'mm/memory.c') diff --git a/mm/memory.c b/mm/memory.c index 7b9db658aca2..5e0e91cc6b67 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -768,7 +768,7 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb, if (pte_dirty(ptent)) set_page_dirty(page); if (pte_young(ptent)) - SetPageReferenced(page); + mark_page_accessed(page); file_rss--; } page_remove_rmap(page, vma); -- cgit v1.2.3