linux-kernel - Re: [PATCH] vmscan: stop meaningless loop iteration when no reclaimable slab

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

On Fri, Jul 9, 2010 at 7:13 PM, KOSAKI Motohiro
<kosaki.motohiro@...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@...fujitsu.com>
> ---
>  mm/vmscan.c |    5 +++++
>  1 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,
>                        int nr_before;
>
>                        nr_before = (*shrinker->shrink)(0, gfp_mask);
> +                       /* no slab objects, no more reclaim. */
> +                       if (nr_before == 0) {
> +                               total_scan = 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?

-- 
Kind regards,
Minchan Kim
--
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