linux-kernel - Re: [PATCHv9 28/36] mm, numa: skip PTE-mapped THP on numa fault

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Message-ID: <55BB8ED8.7090803@redhat.com>
Date:	Fri, 31 Jul 2015 17:06:00 +0200
From:	Jerome Marchand <jmarchan@...hat.com>
To:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Hugh Dickins <hughd@...gle.com>
CC:	Dave Hansen <dave.hansen@...el.com>, Mel Gorman <mgorman@...e.de>,
	Rik van Riel <riel@...hat.com>,
	Vlastimil Babka <vbabka@...e.cz>,
	Christoph Lameter <cl@...two.org>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>,
	Steve Capper <steve.capper@...aro.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...e.cz>,
	Sasha Levin <sasha.levin@...cle.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCHv9 28/36] mm, numa: skip PTE-mapped THP on numa fault

On 07/20/2015 04:21 PM, Kirill A. Shutemov wrote:
> We're going to have THP mapped with PTEs. It will confuse numabalancing.
> Let's skip them for now.

Fair enough.

Acked-by: Jerome Marchand <jmarchan@...hat.com>

> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> Tested-by: Sasha Levin <sasha.levin@...cle.com>
> Tested-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
> ---
>  mm/memory.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index 074edab89b52..52f6fa02c099 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -3186,6 +3186,12 @@ static int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
>  		return 0;
>  	}
>  
> +	/* TODO: handle PTE-mapped THP */
> +	if (PageCompound(page)) {
> +		pte_unmap_unlock(ptep, ptl);
> +		return 0;
> +	}
> +
>  	/*
>  	 * Avoid grouping on RO pages in general. RO pages shouldn't hurt as
>  	 * much anyway since they can be in shared cache state. This misses
> 



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