linux-kernel - Re: [RFC PATCH v2] SLUB: enhance slub to handle memory nodes without normal memory

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Message-ID: <alpine.DEB.2.00.1207251029190.32678@router.home>
Date:	Wed, 25 Jul 2012 10:31:51 -0500 (CDT)
From:	Christoph Lameter <cl@...ux.com>
To:	Jiang Liu <liuj97@...il.com>
cc:	Jiang Liu <jiang.liu@...wei.com>, WuJianguo <wujianguo@...wei.com>,
	Tony Luck <tony.luck@...el.com>,
	Pekka Enberg <penberg@...nel.org>,
	Matt Mackall <mpm@...enic.com>, Mel Gorman <mgorman@...e.de>,
	Yinghai Lu <yinghai@...nel.org>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	David Rientjes <rientjes@...gle.com>,
	Minchan Kim <minchan@...nel.org>,
	Keping Chen <chenkeping@...wei.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2] SLUB: enhance slub to handle memory nodes without
 normal memory

On Wed, 25 Jul 2012, Jiang Liu wrote:

> > There is already a N_NORMAL_MEMORY node map that contains a list of node
> > that have *normal* memory usable by slab allocators etc. I think the
> > cleanest solution would be to clear the corresponding node bits for your
> > special movable only zones. Then you wont be needing to modify other
> > subsystems anymore.
> >
> Hi Chris,
> 	Thanks for your comments! I have thought about the solution mentioned,
> but seems it doesn't work. We have node masks for both N_NORMAL_MEMORY and
> N_HIGH_MEMORY to distinguish between normal and highmem on platforms such as x86.
> But we still don't have such a mechanism to distinguish between "normal" and "movable"
> memory. So for memory nodes with only movable zones, we still set N_NORMAL_MEMORY for
> them. One possible solution is to add a node mask for "N_NORMAL_OR_MOVABLE_MEMORY",
> but haven't tried that yet. Will have a try for that.

Hmmm... Maybe add another N_LRU_MEMORY bitmask and replace those
N_NORMAL_MEMORY uses with N_LRU_MEMORY as needed? Use N_NORMAL_MEMORY for
subsystems that need to do regular (non LRU) allocations that are not
movable?
_
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