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References: <20090514231555.f52c81eb.minchan.kim@gmail.com>
	 <2f11576a0905140727j5ba02b07t94826f57dd99839c@mail.gmail.com>
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>
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Sender: owner-linux-mm@kvack.org
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>
List-ID: <linux-mm.kvack.org>

On Thu, May 14, 2009 at 11:27 PM, KOSAKI Motohiro
<kosaki.motohiro@jp.fujitsu.com> wrote:
>> =C2=A0mm/vmscan.c | =C2=A0 =C2=A02 +-
>> =C2=A01 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,
>> =C2=A0 =C2=A0 =C2=A0 =C2=A0 * Even if we did not try to evict anon pages=
 at all, we want to
>> =C2=A0 =C2=A0 =C2=A0 =C2=A0 * rebalance the anon lru active/inactive rat=
io.
>> =C2=A0 =C2=A0 =C2=A0 =C2=A0 */
>> - =C2=A0 =C2=A0 =C2=A0 if (inactive_anon_is_low(zone, sc))
>> + =C2=A0 =C2=A0 =C2=A0 if (inactive_anon_is_low(zone, sc) && nr_swap_pag=
es > 0)
>> =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0 =C2=A0shrink_active_lis=
t(SWAP_CLUSTER_MAX, zone, sc, priority, 0);
>
>
> =C2=A0 =C2=A0 =C2=A0 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=3Dn as Rik mentioned,
we don't have a concern.

--=20
Thanks,
Minchan Kim

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