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References: <20090514231555.f52c81eb.minchan.kim@gmail.com>
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Date: Thu, 14 May 2009 23:39:49 +0900
Message-ID: <44c63dc40905140739n271d3d2w2e0cc364c0012d71@mail.gmail.com>
Subject: Re: [PATCH] mmtom: Prevent shrinking of active anon lru list in case 
	of no swap space V3
From: Minchan Kim <barrioskmc@gmail.com>
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: MinChan Kim <minchan.kim@gmail.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       LKML <linux-kernel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>,
       Johannes Weiner <hannes@cmpxchg.org>, Rik van Riel <riel@redhat.com>
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On Thu, May 14, 2009 at 11:27 PM, KOSAKI Motohiro
<kosaki.motohiro@jp.fujitsu.com> wrote:
>>  mm/vmscan.c |    2 +-
>>  1 files changed, 1 insertions(+), 1 deletions(-)
>>
>> diff --git a/mm/vmscan.c b/mm/vmscan.c
>> index 2f9d555..621708f 100644
>> --- a/mm/vmscan.c
>> +++ b/mm/vmscan.c
>> @@ -1577,7 +1577,7 @@ static void shrink_zone(int priority, struct zone *zone,
>>         * Even if we did not try to evict anon pages at all, we want to
>>         * rebalance the anon lru active/inactive ratio.
>>         */
>> -       if (inactive_anon_is_low(zone, sc))
>> +       if (inactive_anon_is_low(zone, sc) && nr_swap_pages > 0)
>>                shrink_active_list(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
>
>
>       if (nr_swap_pages > 0 && inactive_anon_is_low(zone, sc))
>
> is better?
> compiler can't swap evaluate order around &&.

If GCC optimizes away that branch with CONFIG_SWAP=n as Rik mentioned,
we don't have a concern.

-- 
Thanks,
Minchan Kim