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Subject: Re: [PATCH 13/35] autonuma: add page structure fields
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Tue, 29 May 2012 16:54:11 +0200
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To: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Hillf Danton <dhillf@gmail.com>, Dan Smith <danms@us.ibm.com>, Linus Torvalds <torvalds@linux-foundation.org>, Andrew Morton <akpm@linux-foundation.org>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>, Paul Turner <pjt@google.com>, Suresh Siddha <suresh.b.siddha@intel.com>, Mike Galbraith <efault@gmx.de>, "Paul E.
 McKenney" <paulmck@linux.vnet.ibm.com>, Lai Jiangshan <laijs@cn.fujitsu.com>, Bharata B Rao <bharata.rao@gmail.com>, Lee Schermerhorn <Lee.Schermerhorn@hp.com>, Johannes Weiner <hannes@cmpxchg.org>, Srivatsa Vaddagiri <vatsa@linux.vnet.ibm.com>, Christoph Lameter <cl@linux.com>

On Tue, 2012-05-29 at 09:56 -0400, Rik van Riel wrote:
> On 05/29/2012 09:16 AM, Peter Zijlstra wrote:
> > On Fri, 2012-05-25 at 19:02 +0200, Andrea Arcangeli wrote:
>=20
> > 24 bytes per page.. or ~0.6% of memory gone. This is far too great a
> > price to pay.
> >
> > At LSF/MM Rik already suggested you limit the number of pages that can
> > be migrated concurrently and use this to move the extra list_head out o=
f
> > struct page and into a smaller amount of extra structures, reducing the
> > total overhead.
>=20
> For THP, we should be able to track this NUMA info on a
> 2MB page granularity.

Yeah, but that's another x86-only feature, _IF_ we're going to do this
it must be done for all archs that have CONFIG_NUMA, thus we're stuck
with 4k (or other base page size).

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