linux-kernel - Re: [PATCH 2/3 -mmotm-2009-12-10-17-19] Count zero page as file

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Date:	Mon, 28 Dec 2009 19:24:47 +0900
From:	Minchan Kim <minchan.kim@...il.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>
CC:	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Hugh Dickins <hugh.dickins@...cali.co.uk>
Subject: Re: [PATCH 2/3 -mmotm-2009-12-10-17-19] Count zero page as file_rss

I missed Hugh. 

Minchan Kim wrote:
> Long time ago, we counted zero page as file_rss.
> But after reinstanted zero page, we don't do it.
> It means rss of process would be smaller than old.
> 
> It could chage OOM victim selection.
> 
> Kame reported following as
> "Before starting zero-page works, I checked "questions" in lkml and
> found some reports that some applications start to go OOM after zero-page
> removal.
> 
> For me, I know one of my customer's application depends on behavior of
> zero page (on RHEL5). So, I tried to add again it before RHEL6 because
> I think removal of zero-page corrupts compatibility."
> 
> So how about adding zero page as file_rss again for compatibility?
> 
> Signed-off-by: Minchan Kim <minchan.kim@...il.com>
> ---
>  mm/memory.c |    7 +++++--
>  1 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/memory.c b/mm/memory.c
> index 3743fb5..a4ba271 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1995,6 +1995,7 @@ static int do_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
>  	int reuse = 0, ret = 0;
>  	int page_mkwrite = 0;
>  	struct page *dirty_page = NULL;
> +	int zero_pfn = 0;
>  
>  	old_page = vm_normal_page(vma, address, orig_pte);
>  	if (!old_page) {
> @@ -2117,7 +2118,8 @@ gotten:
>  	if (unlikely(anon_vma_prepare(vma)))
>  		goto oom;
>  
> -	if (is_zero_pfn(pte_pfn(orig_pte))) {
> +	zero_pfn = is_zero_pfn(pte_pfn(orig_pte));
> +	if (zero_pfn) {
>  		new_page = alloc_zeroed_user_highpage_movable(vma, address);
>  		if (!new_page)
>  			goto oom;
> @@ -2147,7 +2149,7 @@ gotten:
>  	 */
>  	page_table = pte_offset_map_lock(mm, pmd, address, &ptl);
>  	if (likely(pte_same(*page_table, orig_pte))) {
> -		if (old_page) {
> +		if (old_page || zero_pfn) {
>  			if (!PageAnon(old_page)) {
>  				dec_mm_counter(mm, file_rss);
>  				inc_mm_counter(mm, anon_rss);
> @@ -2650,6 +2652,7 @@ static int do_anonymous_page(struct mm_struct *mm, struct vm_area_struct *vma,
>  		spin_lock(ptl);
>  		if (!pte_none(*page_table))
>  			goto unlock;
> +		inc_mm_counter(mm, file_rss);
>  		goto setpte;
>  	}
>  
--
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