linux-kernel - Re: [PATCH 04/16] mm: numa: Do not migrate or account for hinting faults on the zero page

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Message-ID: <20130711112102.GF25631@dyad.programming.kicks-ass.net>
Date:	Thu, 11 Jul 2013 13:21:02 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...nel.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 04/16] mm: numa: Do not migrate or account for hinting
 faults on the zero page

On Thu, Jul 11, 2013 at 10:46:48AM +0100, Mel Gorman wrote:
> +++ b/mm/memory.c
> @@ -3560,8 +3560,13 @@ int do_numa_page(struct mm_struct *mm, struct vm_area_struct *vma,
>  	set_pte_at(mm, addr, ptep, pte);
>  	update_mmu_cache(vma, addr, ptep);
>  
> +	/*
> +	 * Do not account for faults against the huge zero page. The read-only

s/huge //

> +	 * data is likely to be read-cached on the local CPUs and it is less
> +	 * useful to know about local versus remote hits on the zero page.
> +	 */
>  	page = vm_normal_page(vma, addr, pte);
> -	if (!page) {
> +	if (!page || is_zero_pfn(page_to_pfn(page))) {
>  		pte_unmap_unlock(ptep, ptl);
>  		return 0;
>  	}
> -- 
> 1.8.1.4
> 
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