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In-Reply-To: <20090625183616.23b55b24.minchan.kim@barrios-desktop>
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Date: Thu, 25 Jun 2009 23:14:45 +0900
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Message-ID: <2f11576a0906250714o5d77db11wd32c1c7139753cb5@mail.gmail.com>
Subject: Re: [PATCH] prevent to reclaim anon page of lumpy reclaim for no swap 
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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Minchan Kim <minchan.kim@gmail.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, Rik van Riel <riel@redhat.com>,
       KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
       linux-mm <linux-mm@kvack.org>, lkml <linux-kernel@vger.kernel.org>
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> This patch prevent to reclaim anon page in case of no swap space.
> VM already prevent to reclaim anon page in various place.
> But it doesnt't prevent it for lumpy reclaim.
>
> It shuffles lru list unnecessary so that it is pointless.

NAK.

1. if system have no swap, add_to_swap() never get swap entry.
   eary check don't improve performance so much.
2. __isolate_lru_page() is not only called lumpy reclaim case, but
also be called
    normal reclaim.
3. if system have no swap, anon pages shuffuling doesn't cause any matter.

Then, I don't think this patch's benefit is bigger than side effect.



> Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
> ---
> ?mm/vmscan.c | ? ?6 ++++++
> ?1 files changed, 6 insertions(+), 0 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 026f452..fb401fe 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -830,7 +830,13 @@ int __isolate_lru_page(struct page *page, int mode, int file)
> ? ? ? ? * When this function is being called for lumpy reclaim, we
> ? ? ? ? * initially look into all LRU pages, active, inactive and
> ? ? ? ? * unevictable; only give shrink_page_list evictable pages.
> +
> + ? ? ? ?* If we don't have enough swap space, reclaiming of anon page
> + ? ? ? ?* is pointless.
> ? ? ? ? */
> + ? ? ? if (nr_swap_pages <= 0 && PageAnon(page))
> + ? ? ? ? ? ? ? return ret;
> +
> ? ? ? ?if (PageUnevictable(page))
> ? ? ? ? ? ? ? ?return ret;
>
> --
> 1.5.4.3
>
>
>
>
> --
> Kinds Regards
> Minchan Kim
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
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