From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx124.postini.com [74.125.245.124]) by kanga.kvack.org (Postfix) with SMTP id 940816B00D2 for ; Mon, 4 Feb 2013 20:43:12 -0500 (EST) Date: Tue, 5 Feb 2013 10:43:08 +0900 From: Minchan Kim Subject: Re: [PATCH 1/2] mm: prevent to add a page to swap if may_writepage is unset Message-ID: <20130205014308.GG2610@blaptop> 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> <50FD530A.6010500@redhat.com> <20130122000954.GH3666@blaptop> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20130122000954.GH3666@blaptop> Sender: owner-linux-mm@kvack.org List-ID: To: Rik van Riel , Luigi Semenzato , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Dan Magenheimer , Sonny Rao , Bryan Freed , Hugh Dickins , Johannes Weiner On Tue, Jan 22, 2013 at 09:09:54AM +0900, Minchan Kim wrote: > On Mon, Jan 21, 2013 at 09:39:06AM -0500, Rik van Riel wrote: > > 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 :) > > Thanks, Rik. > > Oops, I missed to Ccing Luigi. Add him again. > Luigi, Could you test this patch? > Thanks for your endless effort. > > > > > Acked-by: Rik van Riel > > Andrew, I hope Luigi confirms this patch but he seems to be very busy. At a minimum, I tested this patch and passed my test. Could you apply this and remove [2]? Otherwise, should I wait for Luigi? [2] mm: prevent addition of pages to swap if may_writepage is unset