linux-kernel - Re: [PATCH 1/2] mm: prevent to add a page to swap if may

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20130109065612.GB8550@cmpxchg.org>
Date:	Wed, 9 Jan 2013 01:56:12 -0500
From:	Johannes Weiner <hannes@...xchg.org>
To:	Minchan Kim <minchan@...nel.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Dan Magenheimer <dan.magenheimer@...cle.com>,
	Sonny Rao <sonnyrao@...gle.com>,
	Bryan Freed <bfreed@...gle.com>,
	Hugh Dickins <hughd@...gle.com>, Rik van Riel <riel@...hat.com>
Subject: Re: [PATCH 1/2] mm: prevent to add a page to swap if may_writepage
 is unset

On Wed, Jan 09, 2013 at 03:21:13PM +0900, Minchan Kim wrote:
> 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 <semenzato@...gle.com>
> Signed-off-by: Minchan Kim <minchan@...nel.org>

Acked-by: Johannes Weiner <hannes@...xchg.org>

We used to ignore the page's writeback state on isolation in the past,
could you include a reference to since when this problem has been in
the tree?  Also, would it make sense to tag it for one of the stable
trees?
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/