From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx163.postini.com [74.125.245.163]) by kanga.kvack.org (Postfix) with SMTP id 874866B0004 for ; Mon, 21 Jan 2013 09:39:16 -0500 (EST) Message-ID: <50FD530A.6010500@redhat.com> Date: Mon, 21 Jan 2013 09:39:06 -0500 From: Rik van Riel MIME-Version: 1.0 Subject: Re: [PATCH 1/2] mm: prevent to add a page to swap if may_writepage is unset References: <1357712474-27595-1-git-send-email-minchan@kernel.org> <1357712474-27595-2-git-send-email-minchan@kernel.org> <20130116134155.18092f1a.akpm@linux-foundation.org> <20130117005314.GB18669@blaptop> <20130117142238.e32c46d5.akpm@linux-foundation.org> <20130117233641.GA31368@blaptop> <20130121015222.GA3666@blaptop> In-Reply-To: <20130121015222.GA3666@blaptop> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Dan Magenheimer , Sonny Rao , Bryan Freed , Hugh Dickins , Johannes Weiner On 01/20/2013 08:52 PM, Minchan Kim wrote: > From 94086dc7152359d052802c55c82ef19509fe8cce Mon Sep 17 00:00:00 2001 > From: Minchan Kim > Date: Mon, 21 Jan 2013 10:43:43 +0900 > Subject: [PATCH] mm: Use up free swap space before reaching OOM kill > > 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. > He said there was no problem when he disabled laptop_mode. > The problem when I investigate problem is following as. > > Assumption for easy explanation: There are no page cache page in system > because they all are already reclaimed. > > 1. try_to_free_pages disable may_writepage when laptop_mode is enabled. > 2. shrink_inactive_list isolates victim pages from inactive anon lru list. > 3. shrink_page_list adds them to swapcache via add_to_swap but it doesn't > pageout because sc->may_writepage is 0 so the page is rotated back into > inactive anon lru list. The add_to_swap made the page Dirty by SetPageDirty. > 4. 3 couldn't reclaim any pages so do_try_to_free_pages increase priority and > retry reclaim with higher priority. > 5. shrink_inactlive_list try to isolate victim pages from inactive anon lru list > but got failed because it try to isolate pages with ISOLATE_CLEAN mode but > inactive anon lru list is full of dirty pages by 3 so it just returns > without any reclaim progress. > 6. do_try_to_free_pages doesn't set may_writepage due to zero total_scanned. > Because sc->nr_scanned is increased by shrink_page_list but we don't call > shrink_page_list in 5 due to short of isolated pages. > > Above loop is continued until OOM happens. > The problem didn't happen before [1] was merged because old logic's > isolatation in shrink_inactive_list was successful and tried to call > shrink_page_list to pageout them but it still ends up failed to page out > by may_writepage. But important point is that sc->nr_scanned was increased > although we couldn't swap out them so do_try_to_free_pages could set > may_writepages. > > Since [1] was introduced, it's not a good idea any more to depends on > only the number of scanned pages for setting may_writepage. So this patch > adds new trigger point of setting may_writepage as below DEF_PRIOIRTY - 2 > which is used to show the significant memory pressure in VM so it's good > fit for our purpose which would be better to lose power saving or clickety > rather than OOM killing. > > [1] f80c067[mm: zone_reclaim: make isolate_lru_page() filter-aware] > > Reported-by: Luigi Semenzato > Signed-off-by: Minchan Kim Your patch is a nice simplification. I am ok with the change, provided it works for Luigi :) Acked-by: Rik van Riel -- All rights reversed -- 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