From mboxrd@z Thu Jan 1 00:00:00 1970 From: Johannes Weiner Subject: [PATCH -mm] mm: more likely reclaim MADV_SEQUENTIAL mappings Date: Sat, 19 Jul 2008 19:31:49 +0200 Message-ID: <87y73x4w6y.fsf@saeurebad.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: owner-linux-mm@kvack.org Return-Path: To: Andrew Morton Cc: Rik van Riel , Peter Zijlstra , Nossum , linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: File pages accessed only once through sequential-read mappings between fault and scan time are perfect candidates for reclaim. This patch makes page_referenced() ignore these singular references and the pages stay on the inactive list where they likely fall victim to the next reclaim phase. Already activated pages are still treated normally. If they were accessed multiple times and therefor promoted to the active list, we probably want to keep them. Benchmarks show that big (relative to the system's memory) MADV_SEQUENTIAL mappings read sequentially cause much less kernel activity. Especially less LRU moving-around because we never activate read-once pages in the first place just to demote them again. And leaving these perfect reclaim candidates on the inactive list makes it more likely for the real working set to survive the next reclaim scan. Signed-off-by: Johannes Weiner Signed-off-by: Rik van Riel --- mm/rmap.c | 20 +++++++++++++++----- 1 file changed, 15 insertions(+), 5 deletions(-) Benchmark graphs and the test-application can be found here: http://hannes.saeurebad.de/madvseq/ Patch is against -mm, although only tested on good ol' linus-tree as -mmotm wouldn't compile at the moment. --- a/mm/rmap.c +++ b/mm/rmap.c @@ -333,8 +333,18 @@ 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)) { + /* + * If there was just one sequential access to the + * page, ignore it. Otherwise, mark_page_accessed() + * will have promoted the page to the active list and + * it should be kept. + */ + if (VM_SequentialReadHint(vma) && !PageActive(page)) + ClearPageReferenced(page); + else + referenced++; + } /* Pretend the page is referenced if the task has the swap token and is in the middle of a page fault. */ @@ -455,9 +465,6 @@ int page_referenced(struct page *page, i { int referenced = 0; - if (TestClearPageReferenced(page)) - referenced++; - if (page_mapped(page) && page->mapping) { if (PageAnon(page)) referenced += page_referenced_anon(page, mem_cont); @@ -473,6 +480,9 @@ int page_referenced(struct page *page, i } } + if (TestClearPageReferenced(page)) + referenced++; + if (page_test_and_clear_young(page)) referenced++; -- 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