Subject: Re: [RFC 2.6.11-rc2-mm2 7/7] mm: manual page migration --
	sys_page_migrate
From: Dave Hansen <haveblue@us.ibm.com>
To: Robin Holt <holt@sgi.com>
Cc: Ray Bryant <raybry@sgi.com>, Hirokazu Takahashi <taka@valinux.co.jp>,
       Hugh DIckins <hugh@veritas.com>, Andrew Morton <akpm@osdl.org>,
       Marcello Tosatti <marcello@cyclades.com>,
       Ray Bryant <raybry@austin.rr.com>, linux-mm <linux-mm@kvack.org>,
       linux-kernel <linux-kernel@vger.kernel.org>
In-Reply-To: <20050214220148.GA11832@lnx-holt.americas.sgi.com>
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Date: Mon, 14 Feb 2005 14:22:54 -0800
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On Mon, 2005-02-14 at 16:01 -0600, Robin Holt wrote:
> On Mon, Feb 14, 2005 at 10:50:42AM -0800, Dave Hansen wrote:
> > On Mon, 2005-02-14 at 07:52 -0600, Robin Holt wrote:
> > > The node mask is a list of allowed.  This is intended to be as near
> > > to a one-to-one migration path as possible.
> > 
> > If that's the case, it would make the kernel internals a bit simpler to
> > only take a "from" and "to" node, instead of those maps.  You'll end up
> > making multiple syscalls, but that shouldn't be a problem.  
> 
> Then how do you handle overlapping nodes.  If I am doing a 5->4, 4->3,
> 3->2, 2->1 shift in the memory placement and had only a from and to node,
> I would end up calling multiple times.  This would end up in memory shifting
> from 5->4 on the first, 4->3 on the second, ... with the end result of
> all memory shifting to a single node.

Can you give an example of when you'd actually want to do this?

> On a seperate topic, I would guess the syscall time is trivial compared
> to the time to walk the page tables.

I'd certainly agree.

-- Dave

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