linux-kernel - Re: [PATCH 6/7] mm/pagewalk: move pmd_trans_huge

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Date:	Mon, 09 Jun 2014 13:04:08 -0700
From:	Dave Hansen <dave.hansen@...el.com>
To:	Naoya Horiguchi <n-horiguchi@...jp.nec.com>, linux-mm@...ck.org
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>,
	"Kirill A. Shutemov" <kirill@...temov.name>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/7] mm/pagewalk: move pmd_trans_huge_lock() from callbacks
 to common code

On 06/06/2014 03:58 PM, Naoya Horiguchi wrote:
> @@ -6723,14 +6723,9 @@ static int mem_cgroup_count_precharge_pmd(pmd_t *pmd,
>  					struct mm_walk *walk)
>  {
>  	struct vm_area_struct *vma = walk->vma;
> -	spinlock_t *ptl;
>  
> -	if (pmd_trans_huge_lock(pmd, vma, &ptl) == 1) {
> -		if (get_mctgt_type_thp(vma, addr, *pmd, NULL) == MC_TARGET_PAGE)
> -			mc.precharge += HPAGE_PMD_NR;
> -		spin_unlock(ptl);
> -	} else
> -		skip->control = PTWALK_DOWN;
> +	if (get_mctgt_type_thp(vma, addr, *pmd, NULL) == MC_TARGET_PAGE)
> +		mc.precharge += HPAGE_PMD_NR;
>  	return 0;
>  }

I guess my series did two things:
1. move page table walking to the walk_page_range() code
2. make new walk handler that can take arbitrarily-sizes ptes

This does (1) quite nicely and has some nice code savings.  I still
think (2) has some value, and like my approach, but this is definitely a
step in the right direction.
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