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Date: Mon, 09 Jul 2012 11:40:32 -0400
From: Rik van Riel <riel@redhat.com>
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Subject: Re: [PATCH 00/40] AutoNUMA19
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To: Andrea Arcangeli <aarcange@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Hillf Danton <dhillf@gmail.com>, Dan Smith <danms@us.ibm.com>, Peter Zijlstra <a.p.zijlstra@chello.nl>, 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>, Alex Shi <alex.shi@intel.com>, Mauricio Faria de Oliveira <mauricfo@linux.vnet.ibm.com>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, Don Morris <don.morris@hp.com>, Benjamin Herrenschmidt <benh@kernel.crashing.org>

On 06/28/2012 08:55 AM, Andrea Arcangeli wrote:

> o reduced the page_autonuma memory overhead to from 32 to 12 bytes per page

This bit still worries me a little.

Between the compact list management code, the migrate
daemon, the list locking and page queuing and unqueuing
code, we are looking at 1000-2000 lines of code.

I know your reasoning why asynchronous migration done
by a kernel thread should be better than migrate-on-fault,
but there is no actual evidence that it is in fact true.

Would it be an idea to simplify the code for now, and
add the asynchronous migration later on, if there are
compelling benchmark results that show it to be useful?

The amount of source code involved is large enough that
a justification like that would be useful, IMHO...

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