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Date: Tue, 18 Mar 2014 16:14:48 +0100
From: Michal Hocko <mhocko@suse.cz>
Subject: Re: [PATCHv3] mm: implement POSIX_FADV_NOREUSE
Message-ID: <20140318151448.GB8051@dhcp22.suse.cz>
References: <1394533550-18485-1-git-send-email-matthias.wirth@gmail.com>
 <1394812370-13454-1-git-send-email-matthias.wirth@gmail.com>
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To: Matthias Wirth <matthias.wirth@gmail.com>
Cc: Lukas Senger <lukas@fridolin.com>, i4passt@lists.cs.fau.de, Dave Hansen <dave.hansen@linux.intel.com>, Matthew Wilcox <matthew@wil.cx>, Jeff Layton <jlayton@redhat.com>, "J. Bruce Fields" <bfields@fieldses.org>, Andrew Morton <akpm@linux-foundation.org>, Johannes Weiner <hannes@cmpxchg.org>, Rik van Riel <riel@redhat.com>, Lisa Du <cldu@marvell.com>, Minchan Kim <minchan@kernel.org>, Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>, Sasha Levin <sasha.levin@oracle.com>, "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>, Jan Kara <jack@suse.cz>, Mel Gorman <mgorman@suse.de>, Shaohua Li <shli@kernel.org>, Bob Liu <bob.liu@oracle.com>, Seth Jennings <sjenning@linux.vnet.ibm.com>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Rafael Aquini <aquini@redhat.com>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Al Viro <viro@zeniv.linux.org.uk>, Steven Whitehouse <swhiteho@redhat.com>, Fengguang Wu <fengguang.wu@intel.com>, Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>, Lukas Czerner <lczerner@redhat.com>, Damien Ramonda <damien.ramonda@intel.com>, Mark Rutland <mark.rutland@arm.com>, Andrea Arcangeli <aarcange@redhat.com>, David Rientjes <rientjes@google.com>, Khalid Aziz <khalid.aziz@oracle.com>, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org

On Fri 14-03-14 16:52:38, Matthias Wirth wrote:
[...]
> The idea of the patch is to add pages from files with FMODE_NOREUSE at
> the tail of the lru list. Therefore these pages are the first to be
> reclaimed. We added add_to_page_cache_lru_tail and corresponding
> functions, complementing add_to_page_cache_lru.

If this is set before the read then you can end up trashing on those
pages during heavy memory pressure I am afraid. Page would get reclaimed
before the read gets to it.

What you could do instead, I think, is to reclaim pages belonging to
a FMODE_NOREUSE file away when they would be activated normally during
reclaim. That would require tweaking page_check_references which
implements used-once logic currently.

-- 
Michal Hocko
SUSE Labs

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