linux-kernel - Re: [PATCH] update sc->nr_reclaimed after each shrink

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Message-ID: <20160722074913.GD794@dhcp22.suse.cz>
Date:	Fri, 22 Jul 2016 09:49:13 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Zhou Chengming <zhouchengming1@...wei.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	akpm@...ux-foundation.org, vdavydov@...tuozzo.com, riel@...hat.com,
	guohanjun@...wei.com
Subject: Re: [PATCH] update sc->nr_reclaimed after each shrink_slab

On Fri 22-07-16 11:43:30, Zhou Chengming wrote:
> In !global_reclaim(sc) case, we should update sc->nr_reclaimed after each
> shrink_slab in the loop. Because we need the correct sc->nr_reclaimed
> value to see if we can break out.

Does this actually change anything? Maybe I am missing something but
try_to_free_mem_cgroup_pages which is the main entry for the memcg
reclaim doesn't set reclaim_state. I don't remember why... Vladimir?

Have you observed any issues and this patch fixes it or this is just
motivated by the code inspection?

> Signed-off-by: Zhou Chengming <zhouchengming1@...wei.com>
> ---
>  mm/vmscan.c |    5 +++++
>  1 files changed, 5 insertions(+), 0 deletions(-)
> 
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index c4a2f45..47133c3 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -2405,6 +2405,11 @@ static bool shrink_zone(struct zone *zone, struct scan_control *sc,
>  					    memcg, sc->nr_scanned - scanned,
>  					    lru_pages);
>  
> +			if (!global_reclaim(sc) && reclaim_state) {
> +				sc->nr_reclaimed += reclaim_state->reclaimed_slab;
> +				reclaim_state->reclaimed_slab = 0;
> +			}
> +
>  			/* Record the group's reclaim efficiency */
>  			vmpressure(sc->gfp_mask, memcg, false,
>  				   sc->nr_scanned - scanned,
> -- 
> 1.7.7
> 

-- 
Michal Hocko
SUSE Labs