Message-ID: <1338303251.26856.94.camel@twins>
Subject: Re: [PATCH 13/35] autonuma: add page structure fields
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
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>
Date: Tue, 29 May 2012 16:54:11 +0200
In-Reply-To: <4FC4D58A.50800@redhat.com>
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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:
> 
> > 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 of
> > struct page and into a smaller amount of extra structures, reducing the
> > total overhead.
> 
> 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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