linux-kernel - Re: [PATCH] mm/memcontrol: update lruvec counters in mem_cgroup_move

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Message-ID: <20191015082048.GU317@dhcp22.suse.cz>
Date:   Tue, 15 Oct 2019 10:20:48 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, cgroups@...r.kernel.org,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH] mm/memcontrol: update lruvec counters in
 mem_cgroup_move_account

On Tue 15-10-19 11:09:59, Konstantin Khlebnikov wrote:
> Mapped, dirty and writeback pages are also counted in per-lruvec stats.
> These counters needs update when page is moved between cgroups.

Please describe the user visible effect.

> Fixes: 00f3ca2c2d66 ("mm: memcontrol: per-lruvec stats infrastructure")
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>

We want Cc: stable I suspect because broken stats might be really
misleading.

The patch looks ok to me otherwise
Acked-by: Michal Hocko <mhocko@...e.com>

> ---
>  mm/memcontrol.c |   18 ++++++++++++------
>  1 file changed, 12 insertions(+), 6 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index bdac56009a38..363106578876 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5420,6 +5420,8 @@ static int mem_cgroup_move_account(struct page *page,
>  				   struct mem_cgroup *from,
>  				   struct mem_cgroup *to)
>  {
> +	struct lruvec *from_vec, *to_vec;
> +	struct pglist_data *pgdat;
>  	unsigned long flags;
>  	unsigned int nr_pages = compound ? hpage_nr_pages(page) : 1;
>  	int ret;
> @@ -5443,11 +5445,15 @@ static int mem_cgroup_move_account(struct page *page,
>  
>  	anon = PageAnon(page);
>  
> +	pgdat = page_pgdat(page);
> +	from_vec = mem_cgroup_lruvec(pgdat, from);
> +	to_vec = mem_cgroup_lruvec(pgdat, to);
> +
>  	spin_lock_irqsave(&from->move_lock, flags);
>  
>  	if (!anon && page_mapped(page)) {
> -		__mod_memcg_state(from, NR_FILE_MAPPED, -nr_pages);
> -		__mod_memcg_state(to, NR_FILE_MAPPED, nr_pages);
> +		__mod_lruvec_state(from_vec, NR_FILE_MAPPED, -nr_pages);
> +		__mod_lruvec_state(to_vec, NR_FILE_MAPPED, nr_pages);
>  	}
>  
>  	/*
> @@ -5459,14 +5465,14 @@ static int mem_cgroup_move_account(struct page *page,
>  		struct address_space *mapping = page_mapping(page);
>  
>  		if (mapping_cap_account_dirty(mapping)) {
> -			__mod_memcg_state(from, NR_FILE_DIRTY, -nr_pages);
> -			__mod_memcg_state(to, NR_FILE_DIRTY, nr_pages);
> +			__mod_lruvec_state(from_vec, NR_FILE_DIRTY, -nr_pages);
> +			__mod_lruvec_state(to_vec, NR_FILE_DIRTY, nr_pages);
>  		}
>  	}
>  
>  	if (PageWriteback(page)) {
> -		__mod_memcg_state(from, NR_WRITEBACK, -nr_pages);
> -		__mod_memcg_state(to, NR_WRITEBACK, nr_pages);
> +		__mod_lruvec_state(from_vec, NR_WRITEBACK, -nr_pages);
> +		__mod_lruvec_state(to_vec, NR_WRITEBACK, nr_pages);
>  	}
>  
>  #ifdef CONFIG_TRANSPARENT_HUGEPAGE

-- 
Michal Hocko
SUSE Labs