From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757273Ab3AIGVp (ORCPT ); Wed, 9 Jan 2013 01:21:45 -0500 Received: from LGEMRELSE6Q.lge.com ([156.147.1.121]:44917 "EHLO LGEMRELSE6Q.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752237Ab3AIGVS (ORCPT ); Wed, 9 Jan 2013 01:21:18 -0500 X-AuditID: 9c930179-b7c7fae00000255c-ad-50ed0c5cb988 From: Minchan Kim To: Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Dan Magenheimer , Sonny Rao , Bryan Freed , Hugh Dickins , Rik van Riel , Johannes Weiner , Minchan Kim Subject: [PATCH 1/2] mm: prevent to add a page to swap if may_writepage is unset Date: Wed, 9 Jan 2013 15:21:13 +0900 Message-Id: <1357712474-27595-2-git-send-email-minchan@kernel.org> X-Mailer: git-send-email 1.7.9.5 In-Reply-To: <1357712474-27595-1-git-send-email-minchan@kernel.org> References: <1357712474-27595-1-git-send-email-minchan@kernel.org> X-Brightmail-Tracker: AAAAAA== Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Recently, Luigi reported there are lots of free swap space when OOM happens. It's easily reproduced on zram-over-swap, where many instance of memory hogs are running and laptop_mode is enabled. Luigi reported there was no problem when he disabled laptop_mode. The problem when I investigate problem is following as. try_to_free_pages disable may_writepage if laptop_mode is enabled. shrink_page_list adds lots of anon pages in swap cache by add_to_swap, which makes pages Dirty and rotate them to head of inactive LRU without pageout. If it is repeated, inactive anon LRU is full of Dirty and SwapCache pages. In case of that, isolate_lru_pages fails because it try to isolate clean page due to may_writepage == 0. The may_writepage could be 1 only if total_scanned is higher than writeback_threshold in do_try_to_free_pages but unfortunately, VM can't isolate anon pages from inactive anon lru list by above reason and we already reclaimed all file-backed pages. So it ends up OOM killing. This patch prevents to add a page to swap cache unnecessary when may_writepage is unset so anoymous lru list isn't full of Dirty/Swapcache page. So VM can isolate pages from anon lru list, which ends up setting may_writepage to 1 and could swap out anon lru pages. When OOM triggers, I confirmed swap space was full. Reported-by: Luigi Semenzato Signed-off-by: Minchan Kim --- mm/vmscan.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/mm/vmscan.c b/mm/vmscan.c index ff869d2..439cc47 100644 --- a/mm/vmscan.c +++ b/mm/vmscan.c @@ -780,6 +780,8 @@ static unsigned long shrink_page_list(struct list_head *page_list, if (PageAnon(page) && !PageSwapCache(page)) { if (!(sc->gfp_mask & __GFP_IO)) goto keep_locked; + if (!sc->may_writepage) + goto keep_locked; if (!add_to_swap(page)) goto activate_locked; may_enter_fs = 1; -- 1.7.9.5