linux-kernel - Re: [patch] mm, thp: do not allow thp faults to avoid cpuset restrictions

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Date:	Wed, 23 Jul 2014 18:20:38 -0500
From:	Alex Thorlton <athorlton@....com>
To:	David Rientjes <rientjes@...gle.com>
Cc:	Alex Thorlton <athorlton@....com>,
	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, Mel Gorman <mgorman@...e.de>,
	Rik van Riel <riel@...hat.com>,
	kirill.shutemov@...ux.intel.com, Ingo Molnar <mingo@...nel.org>,
	Hugh Dickins <hughd@...gle.com>, lliubbo@...il.com,
	Johannes Weiner <hannes@...xchg.org>,
	srivatsa.bhat@...ux.vnet.ibm.com,
	Dave Hansen <dave.hansen@...ux.intel.com>, dfults@....com,
	hedi@....com
Subject: Re: [patch] mm, thp: do not allow thp faults to avoid cpuset
 restrictions

On Wed, Jul 23, 2014 at 03:50:09PM -0700, David Rientjes wrote:
> The page allocator relies on __GFP_WAIT to determine if ALLOC_CPUSET 
> should be set in allocflags.  ALLOC_CPUSET controls if a page allocation 
> should be restricted only to the set of allowed cpuset mems.
> 
> Transparent hugepages clears __GFP_WAIT when defrag is disabled to prevent 
> the fault path from using memory compaction or direct reclaim.  Thus, it 
> is unfairly able to allocate outside of its cpuset mems restriction as a 
> side-effect.
> 
> This patch ensures that ALLOC_CPUSET is only cleared when the gfp mask is 
> truly GFP_ATOMIC by verifying it is also not a thp allocation.

Tested.  Works as expected.

Tested-by: Alex Thorlton <athorlton@....com>
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