linux-kernel - Re: [patch] mm: memcontrol: switch soft limit default back to infinity

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Message-ID: <20141229082229.GA32618@dhcp22.suse.cz>
Date:	Mon, 29 Dec 2014 09:22:29 +0100
From:	Michal Hocko <mhocko@...e.cz>
To:	Johannes Weiner <hannes@...xchg.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Vladimir Davydov <vdavydov@...allels.com>,
	Tejun Heo <tj@...nel.org>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [patch] mm: memcontrol: switch soft limit default back to
 infinity

On Sun 28-12-14 13:47:48, Johannes Weiner wrote:
> 3e32cb2e0a12 ("mm: memcontrol: lockless page counters") accidentally
> switched the soft limit default from infinity to zero, which turns all

Should have noticed that during the review :/

> memcgs with even a single page into soft limit excessors and engages
> soft limit reclaim on all of them during global memory pressure.  This
> makes global reclaim generally more aggressive, but also inverts the
> meaning of existing soft limit configurations where unset soft limits
> are usually more generous than set ones.
> 
> Signed-off-by: Johannes Weiner <hannes@...xchg.org>

Acked-by: Michal Hocko <mhocko@...e.cz>

Thanks!

> ---
>  mm/memcontrol.c | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index ef91e856c7e4..b7104a55ae64 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -4679,6 +4679,7 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
>  	if (parent_css == NULL) {
>  		root_mem_cgroup = memcg;
>  		page_counter_init(&memcg->memory, NULL);
> +		memcg->soft_limit = PAGE_COUNTER_MAX;
>  		page_counter_init(&memcg->memsw, NULL);
>  		page_counter_init(&memcg->kmem, NULL);
>  	}
> @@ -4724,6 +4725,7 @@ mem_cgroup_css_online(struct cgroup_subsys_state *css)
>  
>  	if (parent->use_hierarchy) {
>  		page_counter_init(&memcg->memory, &parent->memory);
> +		memcg->soft_limit = PAGE_COUNTER_MAX;
>  		page_counter_init(&memcg->memsw, &parent->memsw);
>  		page_counter_init(&memcg->kmem, &parent->kmem);
>  
> @@ -4733,6 +4735,7 @@ mem_cgroup_css_online(struct cgroup_subsys_state *css)
>  		 */
>  	} else {
>  		page_counter_init(&memcg->memory, NULL);
> +		memcg->soft_limit = PAGE_COUNTER_MAX;
>  		page_counter_init(&memcg->memsw, NULL);
>  		page_counter_init(&memcg->kmem, NULL);
>  		/*
> @@ -4807,7 +4810,7 @@ static void mem_cgroup_css_reset(struct cgroup_subsys_state *css)
>  	mem_cgroup_resize_limit(memcg, PAGE_COUNTER_MAX);
>  	mem_cgroup_resize_memsw_limit(memcg, PAGE_COUNTER_MAX);
>  	memcg_update_kmem_limit(memcg, PAGE_COUNTER_MAX);
> -	memcg->soft_limit = 0;
> +	memcg->soft_limit = PAGE_COUNTER_MAX;
>  }
>  
>  #ifdef CONFIG_MMU
> -- 
> 2.2.0
> 

-- 
Michal Hocko
SUSE Labs
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