From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoph Lameter <cl@linux.com>
Subject: Re: Best way to pin a page in ext4?
Date: Tue, 16 Sep 2014 22:31:24 -0500 (CDT)
Message-ID: <alpine.DEB.2.11.1409162230160.12769@gentwo.org>
References: <20140915185102.0944158037A@closure.thunk.org> <36321733-F488-49E3-8733-C6758F83DFA1@dilger.ca> <20140916180759.GI6205@thunk.org> <alpine.LSU.2.11.1409161555120.5144@eggly.anvils>
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Cc: Theodore Ts'o <tytso@mit.edu>, Andreas Dilger <adilger@dilger.ca>,
    Peter Zijlstra <peterz@infradead.org>, linux-mm <linux-mm@kvack.org>,
    linux-ext4@vger.kernel.org
To: Hugh Dickins <hughd@google.com>
Return-path: <owner-linux-mm@kvack.org>
In-Reply-To: <alpine.LSU.2.11.1409161555120.5144@eggly.anvils>
Sender: owner-linux-mm@kvack.org
List-Id: linux-ext4.vger.kernel.org

On Tue, 16 Sep 2014, Hugh Dickins wrote:

> On the page migration issue: it's not quite as straightforward as
> Christoph suggests.  He and I agree completely that mlocked pages
> should be migratable, but some real-time-minded people disagree:
> so normal compaction is still forbidden to migrate mlocked pages in
> the vanilla kernel (though we in Google patch that prohibition out).
> So pinning by refcount is no worse for compaction than mlocking,
> in the vanilla kernel.

Note though that compaction is not the only mechanism that uses page
migration.

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