linux-kernel - Re: [PATCH for mmotm 2/5]

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Date:	Fri, 12 Jun 2009 07:29:37 +0800
From:	Wu Fengguang <fengguang.wu@...el.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	linux-mm <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
	Mel Gorman <mel@....ul.ie>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH for mmotm 2/5]

On Thu, Jun 11, 2009 at 06:26:48PM +0800, KOSAKI Motohiro wrote:
> Changes since Wu's original patch
>   - adding vmstat
>   - rename NR_TMPFS_MAPPED to NR_SWAP_BACKED_FILE_MAPPED
> 
> 
> ----------------------
> Subject: [PATCH] introduce NR_SWAP_BACKED_FILE_MAPPED zone stat
> 
> Desirable zone reclaim implementaion want to know the number of
> file-backed and unmapped pages.
> 
> Thus, we need to know number of swap-backed mapped pages for
> calculate above number.
> 
> 
> Cc: Mel Gorman <mel@....ul.ie>
> Signed-off-by: Wu Fengguang <fengguang.wu@...el.com>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
> ---
>  include/linux/mmzone.h |    2 ++
>  mm/rmap.c              |    7 +++++++
>  mm/vmstat.c            |    1 +
>  3 files changed, 10 insertions(+)
> 
> Index: b/include/linux/mmzone.h
> ===================================================================
> --- a/include/linux/mmzone.h
> +++ b/include/linux/mmzone.h
> @@ -88,6 +88,8 @@ enum zone_stat_item {
>  	NR_ANON_PAGES,	/* Mapped anonymous pages */
>  	NR_FILE_MAPPED,	/* pagecache pages mapped into pagetables.
>  			   only modified from process context */
> +	NR_SWAP_BACKED_FILE_MAPPED, /* Similar to NR_FILE_MAPPED. but

comment it as "a subset of NR_FILE_MAPPED"?

Why move this 'cold' item to the first hot cache line?

> +				       only account swap-backed pages */
>  	NR_FILE_PAGES,
>  	NR_FILE_DIRTY,
>  	NR_WRITEBACK,
> Index: b/mm/rmap.c
> ===================================================================
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -829,6 +829,10 @@ void page_add_file_rmap(struct page *pag
>  {
>  	if (atomic_inc_and_test(&page->_mapcount)) {
>  		__inc_zone_page_state(page, NR_FILE_MAPPED);
> +		if (PageSwapBacked(page))
> +			__inc_zone_page_state(page,
> +					      NR_SWAP_BACKED_FILE_MAPPED);
> +

The line wrapping is not necessary here.

>  		mem_cgroup_update_mapped_file_stat(page, 1);
>  	}
>  }
> @@ -884,6 +888,9 @@ void page_remove_rmap(struct page *page)
>  		__dec_zone_page_state(page, NR_ANON_PAGES);
>  	} else {
>  		__dec_zone_page_state(page, NR_FILE_MAPPED);
> +		if (PageSwapBacked(page))
> +			__dec_zone_page_state(page,
> +					NR_SWAP_BACKED_FILE_MAPPED);

ditto.

>  	}
>  	mem_cgroup_update_mapped_file_stat(page, -1);
>  	/*
> Index: b/mm/vmstat.c
> ===================================================================
> --- a/mm/vmstat.c
> +++ b/mm/vmstat.c
> @@ -633,6 +633,7 @@ static const char * const vmstat_text[] 
>  	"nr_mlock",
>  	"nr_anon_pages",
>  	"nr_mapped",
> +	"nr_swap_backed_file_mapped",

An overlong name, in my updated patch, I do it this way.

        "nr_bounce",
        "nr_vmscan_write",
        "nr_writeback_temp",
+       "nr_mapped_swapbacked",
 

The "mapped" comes first because I want to emphasis that
this is a subset of nr_mapped.

Thanks,
Fengguang
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