linux-kernel - Re: [patch] mm, thp: always direct reclaim for MADV

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Date:   Fri, 30 Dec 2016 13:56:16 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Mel Gorman <mgorman@...hsingularity.net>
Cc:     David Rientjes <rientjes@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Vlastimil Babka <vbabka@...e.cz>, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org
Subject: Re: [patch] mm, thp: always direct reclaim for MADV_HUGEPAGE even
 when deferred

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.

Also I am planning to send a pro-active compaction based on a
"watermark" as an LSF/MM topic proposal. I suspect that no additional
thp specific tunable will be needed if we have a proper compaction
watermark tunable.
-- 
Michal Hocko
SUSE Labs