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

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Date:   Tue, 15 Oct 2019 12:36:23 +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 11:44:22, Konstantin Khlebnikov wrote:
> On 15/10/2019 11.20, Michal Hocko wrote:
> > 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.
> 
> Surprisingly I don't see any users at this moment.
> So, there is no effect in mainline kernel.

Those counters are exported right? Or do we exclude them for v1?

> > > 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