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

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Message-ID: <20161222083128.GB32480@node.shutemov.name>
Date:   Thu, 22 Dec 2016 11:31:28 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
To:     David Rientjes <rientjes@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Jonathan Corbet <corbet@....net>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Mel Gorman <mgorman@...hsingularity.net>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [patch] mm, thp: always direct reclaim for MADV_HUGEPAGE even
 when deferred

On Wed, Dec 21, 2016 at 04:21:54PM -0800, David Rientjes wrote:
> Currently, when defrag is set to "madvise", thp allocations will direct
> reclaim.  However, when defrag is set to "defer", all thp allocations do
> not attempt reclaim regardless of MADV_HUGEPAGE.
> 
> This patch always directly reclaims for MADV_HUGEPAGE regions when defrag
> is not set to "never."  The idea is that MADV_HUGEPAGE regions really
> want to be backed by hugepages and are willing to endure the latency at
> fault as it was the default behavior prior to commit 444eb2a449ef ("mm:
> thp: set THP defrag by default to madvise and add a stall-free defrag
> option").
> 
> In this form, "defer" is a stronger, more heavyweight version of
> "madvise".
> 
> Signed-off-by: David Rientjes <rientjes@...gle.com>

Makes senses to me.

Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>

-- 
 Kirill A. Shutemov