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Subject: Re: [RFC][PATCH 00/26] sched/numa
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Avi Kivity <avi@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@elte.hu>,
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        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>, Dan Smith <danms@us.ibm.com>,
        Bharata B Rao <bharata.rao@gmail.com>,
        Lee Schermerhorn <Lee.Schermerhorn@hp.com>,
        Andrea Arcangeli <aarcange@redhat.com>, Rik van Riel <riel@redhat.com>,
        Johannes Weiner <hannes@cmpxchg.org>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org
Date: Mon, 19 Mar 2012 21:03:07 +0100
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On Mon, 2012-03-19 at 14:16 +0200, Avi Kivity wrote:
> > Afaik we do not use dma engines for memory migration. 
> 
> We don't, but I think we should. 

ISTR we (the community) had this discussion once. I also seem to
remember the general consensus being that DMA engines would mostly
likely not be worth the effort, although I can't really recall the
specifics.

Esp. for 4k pages the setup of the offload will likely be more expensive
than actually doing the memcpy.