linux-kernel - Re: [PATCHv3 05/24] mm, proc: adjust PSS calculation

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Date:	Fri, 20 Feb 2015 18:31:15 +0100
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>, linux-kernel@...r.kernel.org,
	linux-mm@...ck.org
Subject: Re: [PATCHv3 05/24] mm, proc: adjust PSS calculation

On 02/12/2015 05:18 PM, Kirill A. Shutemov wrote:
> With new refcounting all subpages of the compound page are not nessessary
> have the same mapcount. We need to take into account mapcount of every
> sub-page.
> 
> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
> ---
>  fs/proc/task_mmu.c | 43 ++++++++++++++++++++++---------------------
>  1 file changed, 22 insertions(+), 21 deletions(-)
> 
> diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> index 98826d08a11b..8a0a78174cc6 100644
> --- a/fs/proc/task_mmu.c
> +++ b/fs/proc/task_mmu.c
> @@ -449,9 +449,10 @@ struct mem_size_stats {
>  };
>  
>  static void smaps_account(struct mem_size_stats *mss, struct page *page,
> -		unsigned long size, bool young, bool dirty)
> +		bool compound, bool young, bool dirty)
>  {
> -	int mapcount;
> +	int i, nr = compound ? hpage_nr_pages(page) : 1;
> +	unsigned long size = 1UL << nr;

Shouldn't that be:
	unsigned long size = nr << PAGE_SHIFT;

>  
>  	if (PageAnon(page))
>  		mss->anonymous += size;
> @@ -460,23 +461,23 @@ static void smaps_account(struct mem_size_stats *mss, struct page *page,
>  	/* Accumulate the size in pages that have been accessed. */
>  	if (young || PageReferenced(page))
>  		mss->referenced += size;
> -	mapcount = page_mapcount(page);
> -	if (mapcount >= 2) {
> -		u64 pss_delta;
>  
> -		if (dirty || PageDirty(page))
> -			mss->shared_dirty += size;
> -		else
> -			mss->shared_clean += size;
> -		pss_delta = (u64)size << PSS_SHIFT;
> -		do_div(pss_delta, mapcount);
> -		mss->pss += pss_delta;
> -	} else {
> -		if (dirty || PageDirty(page))
> -			mss->private_dirty += size;
> -		else
> -			mss->private_clean += size;
> -		mss->pss += (u64)size << PSS_SHIFT;
> +	for (i = 0; i < nr; i++) {
> +		int mapcount = page_mapcount(page + i);
> +
> +		if (mapcount >= 2) {
> +			if (dirty || PageDirty(page + i))
> +				mss->shared_dirty += PAGE_SIZE;
> +			else
> +				mss->shared_clean += PAGE_SIZE;
> +			mss->pss += (PAGE_SIZE << PSS_SHIFT) / mapcount;
> +		} else {
> +			if (dirty || PageDirty(page + i))
> +				mss->private_dirty += PAGE_SIZE;
> +			else
> +				mss->private_clean += PAGE_SIZE;
> +			mss->pss += PAGE_SIZE << PSS_SHIFT;
> +		}
>  	}
>  }
>  
> @@ -500,7 +501,8 @@ static void smaps_pte_entry(pte_t *pte, unsigned long addr,
>  
>  	if (!page)
>  		return;
> -	smaps_account(mss, page, PAGE_SIZE, pte_young(*pte), pte_dirty(*pte));
> +
> +	smaps_account(mss, page, false, pte_young(*pte), pte_dirty(*pte));
>  }
>  
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE
> @@ -516,8 +518,7 @@ static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
>  	if (IS_ERR_OR_NULL(page))
>  		return;
>  	mss->anonymous_thp += HPAGE_PMD_SIZE;
> -	smaps_account(mss, page, HPAGE_PMD_SIZE,
> -			pmd_young(*pmd), pmd_dirty(*pmd));
> +	smaps_account(mss, page, true, pmd_young(*pmd), pmd_dirty(*pmd));
>  }
>  #else
>  static void smaps_pmd_entry(pmd_t *pmd, unsigned long addr,
> 



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