linux-kernel - Re: [PATCH] page_alloc: skip cpuset enforcement for lower zone allocations (v4)

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Message-Id: <20140529161253.73ff978f723972f503123fe8@linux-foundation.org>
Date:	Thu, 29 May 2014 16:12:53 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Marcelo Tosatti <mtosatti@...hat.com>,
	Li Zefan <lizefan@...wei.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Lai Jiangshan <laijs@...fujitsu.com>,
	Mel Gorman <mgorman@...e.de>, Tejun Heo <tj@...nel.org>,
	Christoph Lameter <cl@...ux.com>
Subject: Re: [PATCH] page_alloc: skip cpuset enforcement for lower zone
 allocations (v4)

On Thu, 29 May 2014 16:01:55 -0700 (PDT) David Rientjes <rientjes@...gle.com> wrote:

> There are still three issues with this, two of which are only minor and 
> one that needs more thought:
> 
>  (1) this doesn't affect only cpusets which the changelog indicates, it 
>      also bypasses mempolicies for GFP_DMA and GFP_DMA32 allocations since
>      the nodemask != NULL in the page allocator when there is an effective
>      mempolicy.  That may be precisely what you're trying to do (do the
>      same for mempolicies as you're doing for cpusets), but the comment 
>      now in the code specifically refers to cpusets.  Can you make a case
>      for the mempolicies exception as well?  Otherwise, we'll need to do
> 
> 	if (!nodemask && gfp_zone(gfp_mask) < policy_zone)
> 		nodemask = &node_states[N_ONLINE];
> 
> And the two minors:
> 
>  (2) this should be &node_states[N_MEMORY], not &node_states[N_ONLINE] 
>      since memoryless nodes should not be included.  Note that
>      guarantee_online_mems() looks at N_MEMORY and
>      cpuset_current_mems_allowed is defined for N_MEMORY without
>      cpusets.
> 
>  (3) it's unnecessary for this to be after the "retry_cpuset" label and
>      check the gfp mask again if we need to relook at the allowed cpuset
>      mask.

OK, thanks, I made the patch go away for now.
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