linux-kernel - Re: [RFC][PATCH 1/5] mm: Introduce VM

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Message-ID: <20140529080134.GC30445@twins.programming.kicks-ass.net>
Date:	Thu, 29 May 2014 10:01:34 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Rik van Riel <riel@...hat.com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Christoph Lameter <cl@...ux.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Roland Dreier <roland@...nel.org>,
	Sean Hefty <sean.hefty@...el.com>,
	Hal Rosenstock <hal.rosenstock@...il.com>,
	Mike Marciniszyn <infinipath@...el.com>
Subject: Re: [RFC][PATCH 1/5] mm: Introduce VM_PINNED and interfaces

On Wed, May 28, 2014 at 09:48:43PM -0400, Rik van Riel wrote:
> On 05/26/2014 10:56 AM, Peter Zijlstra wrote:
> 
> >  include/linux/mm.h       |    3 +
> >  include/linux/mm_types.h |    5 +
> >  kernel/fork.c            |    2 
> >  mm/mlock.c               |  133 ++++++++++++++++++++++++++++++++++++++++++-----
> >  mm/mmap.c                |   18 ++++--
> >  5 files changed, 141 insertions(+), 20 deletions(-)
> 
> I'm guessing you will also want a patch that adds some code to
> rmap.c, madvise.c, and a few other places to actually enforce
> the VM_PINNED semantics?

Eventually, yes. As it stands they're not needed, because perf pages
aren't in the pagecache and IB goes a big get_user_pages() and the
elevated refcount stops everything dead.

But yes, once we go do fancy things like migrate the pages into
UNMOVABLE blocks, then we need to have VM_PINNED itself mean something,
instead of it describing something.

But before we go down there, I'd like to get the IB bits sorted and
general agreement on the path.

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