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Date: Fri, 9 Jul 2010 19:53:13 +0900
Message-ID: <AANLkTins0OMGnj3JmUjIctO0dSnXPsQV1AUsbMEVt2D1@mail.gmail.com>
Subject: Re: [PATCH] vmscan: stop meaningless loop iteration when no
	reclaimable slab
From: Minchan Kim <minchan.kim@gmail.com>
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Sender: owner-linux-mm@kvack.org
To: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Andrew Morton <akpm@linux-foundation.org>, Christoph Lameter <cl@linux-foundation.org>, LKML <linux-kernel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>, Mel Gorman <mel@csn.ul.ie>, Rik van Riel <riel@redhat.com>, Johannes Weiner <hannes@cmpxchg.org>
List-ID: <linux-mm.kvack.org>

On Fri, Jul 9, 2010 at 7:13 PM, KOSAKI Motohiro
<kosaki.motohiro@jp.fujitsu.com> wrote:
> If number of reclaimable slabs are zero, shrink_icache_memory() and
> shrink_dcache_memory() return 0. but strangely shrink_slab() ignore
> it and continue meaningless loop iteration.
>
> This patch fixes it.
>
> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> ---
> =A0mm/vmscan.c | =A0 =A05 +++++
> =A01 files changed, 5 insertions(+), 0 deletions(-)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 0f9f624..8f61adb 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -243,6 +243,11 @@ unsigned long shrink_slab(unsigned long scanned, gfp=
_t gfp_mask,
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0int nr_before;
>
> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0nr_before =3D (*shrinker->=
shrink)(0, gfp_mask);
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 /* no slab objects, no more=
 reclaim. */
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 if (nr_before =3D=3D 0) {
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 total_scan =
=3D 0;

Why do you reset totoal_scan to 0?
I don't know exact meaning of shrinker->nr.
AFAIU, it can affect next shrinker's total_scan.
Isn't it harmful?

--=20
Kind regards,
Minchan Kim

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