From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 6 Nov 2008 10:55:13 +0100 From: Johannes Weiner Subject: [PATCH -v2] mm: more likely reclaim MADV_SEQUENTIAL mappings Message-ID: <20081106095513.GA4639@cmpxchg.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: Rik van Riel , KOSAKI Motohiro , Nick Piggin , Linux Memory Management List List-ID: 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. Signed-off-by: Johannes Weiner Signed-off-by: Rik van Riel Acked-by: KOSAKI Motohiro CC: Nick Piggin --- II: add likely()s to mitigate the extra branches a bit as to Nick's suggestion Benchmark results from KOSAKI Motohiro: http://marc.info/?l=linux-mm&m=122485301925098&w=2 mm/memory.c | 3 ++- mm/rmap.c | 13 +++++++++++-- 2 files changed, 13 insertions(+), 3 deletions(-) --- a/mm/rmap.c +++ b/mm/rmap.c @@ -337,8 +337,17 @@ static int page_referenced_one(struct pa goto out_unmap; } - if (ptep_clear_flush_young_notify(vma, address, pte)) - referenced++; + if (ptep_clear_flush_young_notify(vma, address, pte)) { + /* + * Don't treat a reference through a sequentially read + * mapping as such. If the page has been used in + * another mapping, we will catch it; if this other + * mapping is already gone, the unmap path will have + * set PG_referenced or activated the page. + */ + if (likely(!VM_SequentialReadHint(vma))) + referenced++; + } /* Pretend the page is referenced if the task has the swap token and is in the middle of a page fault. */ --- a/mm/memory.c +++ b/mm/memory.c @@ -759,7 +759,8 @@ static unsigned long zap_pte_range(struc 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--; } -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org