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Date: Tue, 27 May 2014 18:43:41 +0200
From: Peter Zijlstra <peterz@infradead.org>
Subject: Re: [RFC][PATCH 0/5] VM_PINNED
Message-ID: <20140527164341.GD11074@laptop.programming.kicks-ass.net>
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To: Christoph Lameter <cl@gentwo.org>
Cc: Konstantin Khlebnikov <koct9i@gmail.com>, "linux-mm@kvack.org" <linux-mm@kvack.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, Thomas Gleixner <tglx@linutronix.de>, Andrew Morton <akpm@linux-foundation.org>, Hugh Dickins <hughd@google.com>, Mel Gorman <mgorman@suse.de>, Roland Dreier <roland@kernel.org>, Sean Hefty <sean.hefty@intel.com>, Hal Rosenstock <hal.rosenstock@gmail.com>, Mike Marciniszyn <infinipath@intel.com>

On Tue, May 27, 2014 at 11:31:21AM -0500, Christoph Lameter wrote:
> On Tue, 27 May 2014, Peter Zijlstra wrote:
> 
> > On Tue, May 27, 2014 at 10:14:10AM -0500, Christoph Lameter wrote:
> > > On Tue, 27 May 2014, Peter Zijlstra wrote:
> > >
> > > > Well, like with IB, they start out as normal userspace pages, and will
> > > > be from ZONE_MOVABLE.
> > >
> > > Well we could change that now I think. If the VMA has VM_PINNED set
> > > pages then do not allocate from ZONE_MOVABLE.
> >
> > But most allocations sites don't have the vma. We allocate page-cache
> > pages based on its address_space/mapping, not on whatever vma they're
> > mapped into.
> 
> Most allocations by the application for an address range also must
> consider a memory allocation policy which is also bound to a vma and we
> have code for that in mm/mempolicy.c
> 
> Code could be easily added to alloc_pages_vma() to consider the pinned
> status on allocation. Remove GFP_MOVABLE if the vma is pinned.

Yes, but alloc_pages_vma() isn't used for shared pages (with exception
of shmem and hugetlbfs).

So whichever way around we have to do the mm_populate() + eviction hook
+ migration code, and since that equally covers the anon case, why
bother?


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