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Date: Fri, 11 Jul 2014 12:24:51 -0400
From: Tejun Heo <tj@kernel.org>
Subject: Re: [RFC Patch V1 07/30] mm: Use cpu_to_mem()/numa_mem_id() to
 support memoryless node
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References: <1405064267-11678-1-git-send-email-jiang.liu@linux.intel.com>
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To: Christoph Lameter <cl@gentwo.org>
Cc: Jiang Liu <jiang.liu@linux.intel.com>, Andrew Morton <akpm@linux-foundation.org>, Mel Gorman <mgorman@suse.de>, David Rientjes <rientjes@google.com>, Mike Galbraith <umgwanakikbuti@gmail.com>, Peter Zijlstra <peterz@infradead.org>, "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>, Vladimir Davydov <vdavydov@parallels.com>, Johannes Weiner <hannes@cmpxchg.org>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, Rik van Riel <riel@redhat.com>, Wanpeng Li <liwanp@linux.vnet.ibm.com>, Zhang Yanfei <zhangyanfei@cn.fujitsu.com>, Catalin Marinas <catalin.marinas@arm.com>, Jianyu Zhan <nasa4836@gmail.com>, malc <av1474@comtv.ru>, Joonsoo Kim <iamjoonsoo.kim@lge.com>, Fabian Frederick <fabf@skynet.be>, Tony Luck <tony.luck@intel.com>, linux-mm@kvack.org, linux-hotplug@vger.kernel.org, linux-kernel@vger.kernel.org

On Fri, Jul 11, 2014 at 11:19:14AM -0500, Christoph Lameter wrote:
> Yes that works. But if we want a consistent node to allocate from (and
> avoid the fallbacks) then we need this patch. I think this is up to those
> needing memoryless nodes to figure out what semantics they need.

I'm not following what you're saying.  Are you saying that we need to
spread numa_mem_id() all over the place for GFP_THISNODE users on
memless nodes?  There aren't that many users of GFP_THISNODE.
Wouldn't it make far more sense to just change them?  Or just
introduce a new GFP flag GFP_CLOSE_OR_BUST which allows falling back
to the nearest local node for memless nodes.  There's no reason to
leak this information outside allocator proper.

Thanks.

-- 
tejun

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