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Date: Fri, 30 Dec 2016 14:08:39 +0000
From: Mel Gorman <mgorman@techsingularity.net>
To: Michal Hocko <mhocko@kernel.org>
Cc: David Rientjes <rientjes@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Jonathan Corbet <corbet@lwn.net>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Vlastimil Babka <vbabka@suse.cz>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org
Subject: Re: [patch] mm, thp: always direct reclaim for MADV_HUGEPAGE even
 when deferred
Message-ID: <20161230140839.qg3maz4ifyf7nwgq@techsingularity.net>
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On Fri, Dec 30, 2016 at 01:56:16PM +0100, Michal Hocko wrote:
> On Fri 30-12-16 12:36:20, Mel Gorman wrote:
> [...]
> > I'll neither ack nor nak this patch. However, I would much prefer an
> > additional option be added to sysfs called defer-fault that would avoid
> > all fault-based stalls but still potentially stall for MADV_HUGEPAGE.
> 
> Would you consider changing the semantic of defer=madvise to invoke
> KSWAPD for !madvised vmas as acceptable. It would be a change in
> semantic but I am wondering what would be a risk and potential
> regression space.
> 

I'd worry a little, but not a lot. The concern would be that kswapd waking
up would reclaim pages and cause major faults that would have remained
resident with the current semantics.

-- 
Mel Gorman
SUSE Labs