From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Andrea Arcangeli <aarcange@redhat.com>
Subject: Re: [PATCH 64 of 66] scale nr_rotated to balance memory pressure
Cc: kosaki.motohiro@jp.fujitsu.com, linux-mm@kvack.org,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        linux-kernel@vger.kernel.org, Marcelo Tosatti <mtosatti@redhat.com>,
        Adam Litke <agl@us.ibm.com>, Avi Kivity <avi@redhat.com>,
        Hugh Dickins <hugh.dickins@tiscali.co.uk>,
        Rik van Riel <riel@redhat.com>, Mel Gorman <mel@csn.ul.ie>,
        Dave Hansen <dave@linux.vnet.ibm.com>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Ingo Molnar <mingo@elte.hu>, Mike Travis <travis@sgi.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        Christoph Lameter <cl@linux-foundation.org>,
        Chris Wright <chrisw@sous-sol.org>, bpicco@redhat.com,
        Balbir Singh <balbir@linux.vnet.ibm.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp>,
        Chris Mason <chris.mason@oracle.com>, Borislav Petkov <bp@alien8.de>
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References: <patchbomb.1288798055@v2.random> <54b5b2d012ff38e341ad.1288798119@v2.random>
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Date: Tue,  9 Nov 2010 15:16:21 +0900 (JST)
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> From: Rik van Riel <riel@redhat.com>
> 
> Make sure we scale up nr_rotated when we encounter a referenced
> transparent huge page.  This ensures pageout scanning balance
> is not distorted when there are huge pages on the LRU.
> 
> Signed-off-by: Rik van Riel <riel@redhat.com>
> Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
> ---
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -1259,7 +1259,8 @@ putback_lru_pages(struct zone *zone, str
>  		add_page_to_lru_list(zone, page, lru);
>  		if (is_active_lru(lru)) {
>  			int file = is_file_lru(lru);
> -			reclaim_stat->recent_rotated[file]++;
> +			int numpages = hpage_nr_pages(page);
> +			reclaim_stat->recent_rotated[file] += numpages;
>  		}
>  		if (!pagevec_add(&pvec, page)) {
>  			spin_unlock_irq(&zone->lru_lock);

I haven't seen this patch series carefully yet. So, probably
my question is dumb. Why don't we need to change ->recent_scanned[] too?


> @@ -1535,7 +1536,7 @@ static void shrink_active_list(unsigned 
>  		}
>  
>  		if (page_referenced(page, 0, sc->mem_cgroup, &vm_flags)) {
> -			nr_rotated++;
> +			nr_rotated += hpage_nr_pages(page);
>  			/*
>  			 * Identify referenced, file-backed active pages and
>  			 * give them one more trip around the active list. So


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