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Date: Wed, 4 Jul 2012 11:19:55 +0100
From: Mel Gorman <mel@csn.ul.ie>
Subject: Re: [RFC PATCH 2/3 V1] mm, page migrate: add MIGRATE_HOTREMOVE type
Message-ID: <20120704101942.GM13141@csn.ul.ie>
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To: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>, Len Brown <lenb@kernel.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, Andi Kleen <andi@firstfloor.org>, Julia Lawall <julia@diku.dk>, David Howells <dhowells@redhat.com>, Benjamin Herrenschmidt <benh@kernel.crashing.org>, Kay Sievers <kay.sievers@vrfy.org>, Ingo Molnar <mingo@elte.hu>, Paul Gortmaker <paul.gortmaker@windriver.com>, Daniel Kiper <dkiper@net-space.pl>, Andrew Morton <akpm@linux-foundation.org>, Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>, Michal Hocko <mhocko@suse.cz>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>, Minchan Kim <minchan@kernel.org>, Michal Nazarewicz <mina86@mina86.com>, Marek Szyprowski <m.szyprowski@samsung.com>, Rik van Riel <riel@redhat.com>, Bjorn Helgaas <bhelgaas@google.com>, Christoph Lameter <cl@linux.com>, David Rientjes <rientjes@google.com>, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-mm@kvack.org

On Wed, Jul 04, 2012 at 03:26:17PM +0800, Lai Jiangshan wrote:
> MIGRATE_HOTREMOVE is a special kind of MIGRATE_MOVABLE, but it is stable:
> any page of the type can NOT be changed to the other type nor be moved to
> the other free list.
> 
> So the pages of MIGRATE_HOTREMOVE are always movable, this ability is
> useful for hugepages and hotremove ...etc.
> 
> MIGRATE_HOTREMOVE pages is the used as the first candidate when
> we allocate movable pages.
> 
> 1) add small routine is_migrate_movable() for movable-like types
> 2) add small routine is_migrate_stable() for stable types
> 3) fix some comments
> 4) fix get_any_page(). The get_any_page() may change
>    MIGRATE_CMA/HOTREMOVE types page to MOVABLE which may cause this page
>    to be changed to UNMOVABLE.
> 

Reuse MIGRATE_CMA. Even if the pages are on the movable lists it should
not be a problem for memory hot-remove.

-- 
Mel Gorman
SUSE Labs

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