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Date: Tue, 26 Jan 2010 08:53:03 +0200
From: Gleb Natapov <gleb@redhat.com>
Subject: Re: [PATCH 00 of 30] Transparent Hugepage support #3
Message-ID: <20100126065303.GJ8483@redhat.com>
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To: Rik van Riel <riel@redhat.com>
Cc: Christoph Lameter <cl@linux-foundation.org>, Andrea Arcangeli <aarcange@redhat.com>, linux-mm@kvack.org, Marcelo Tosatti <mtosatti@redhat.com>, Adam Litke <agl@us.ibm.com>, Avi Kivity <avi@redhat.com>, Izik Eidus <ieidus@redhat.com>, Hugh Dickins <hugh.dickins@tiscali.co.uk>, Nick Piggin <npiggin@suse.de>, Mel Gorman <mel@csn.ul.ie>, Andi Kleen <andi@firstfloor.org>, Dave Hansen <dave@linux.vnet.ibm.com>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Ingo Molnar <mingo@elte.hu>, Mike Travis <travis@sgi.com>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, Chris Wright <chrisw@sous-sol.org>, Andrew Morton <akpm@linux-foundation.org>
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On Mon, Jan 25, 2010 at 07:52:16PM -0500, Rik van Riel wrote:
> On 01/25/2010 04:50 PM, Christoph Lameter wrote:
> 
> >So its not possible to use these "huge" pages in a useful way inside of
> >the kernel. They are volatile and temporary.
> 
> >In short they cannot be treated as 2M entities unless we add some logic to
> >prevent splitting.
> >
> >Frankly this seems to be adding splitting that cannot be used if one
> >really wants to use large pages for something.
> 
> What exactly do you need the stable huge pages for?
> 
> Do you have anything specific in mind that we should take
> into account?
> 
> Want to send in an incremental patch that can temporarily block
> the pageout code from splitting up a huge page, so your direct
> users of huge pages can rely on them sticking around until the
> transaction is done?
> 
Shouldn't mlock() do the trick?

--
			Gleb.

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