From: Peter Zijlstra <peterz@infradead.org>
To: Hugh Dickins <hughd@google.com>
Cc: Theodore Ts'o <tytso@mit.edu>, Andreas Dilger <adilger@dilger.ca>,
Christoph Lameter <cl@linux.com>, linux-mm <linux-mm@kvack.org>,
linux-ext4@vger.kernel.org
Subject: Re: Best way to pin a page in ext4?
Date: Wed, 17 Sep 2014 15:56:14 +0200 [thread overview]
Message-ID: <20140917135614.GJ2840@worktop.localdomain> (raw)
In-Reply-To: <alpine.LSU.2.11.1409161555120.5144@eggly.anvils>
On Tue, Sep 16, 2014 at 05:07:18PM -0700, 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.
These realtime people are fully aware of this -- they should be at
least, I've been telling them for years.
Also, they would be very happy with means to actually pin pages -- as
per the patches Christoph referred to. The advantage of also having
mpin() and co is that we can migrate the memory into non-movable blocks
before returning etc.
In any case, I think we can (and should) change the behaviour of mlock
to be migratable (possibly with an easy way to revert in -rt for
migratory purposes until we get mpin sorted).
--
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prev parent reply other threads:[~2014-09-17 13:56 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-15 18:51 Theodore Ts'o
2014-09-15 20:57 ` Andreas Dilger
2014-09-16 18:07 ` Theodore Ts'o
2014-09-16 18:34 ` Christoph Lameter
2014-09-16 18:56 ` Theodore Ts'o
2014-09-17 0:07 ` Hugh Dickins
2014-09-17 1:25 ` Theodore Ts'o
2014-09-17 3:31 ` Christoph Lameter
2014-09-17 13:57 ` Peter Zijlstra
2014-09-17 20:37 ` Hugh Dickins
2014-09-17 13:56 ` Peter Zijlstra [this message]
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