Re: [PATCH v1 4/5] mm: memcg: charge memcg percpu memory to the parent cgroup

[Dennis Zhou <dennis@kernel.org>]

On Thu, May 28, 2020 at 04:25:07PM -0700, Roman Gushchin wrote:
> Memory cgroups are using large chunks of percpu memory to store
> vmstat data. Yet this memory is not accounted at all, so in the
> case when there are many (dying) cgroups, it's not exactly clear
> where all the memory is.
> 
> Because the size of  memory cgroup internal structures can
> dramatically exceed the size of object or page which is pinning
> it in the memory, it's not a good idea to simple ignore it.
> It actually breaks the isolation between cgroups.
> 
> Let's account the consumed percpu memory to the parent cgroup.
> 
> Signed-off-by: Roman Gushchin <guro@fb.com>
> ---
>  mm/memcontrol.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 5007d1585a4a..0dd0d05a011c 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5020,13 +5020,15 @@ static int alloc_mem_cgroup_per_node_info(struct mem_cgroup *memcg, int node)
>  	if (!pn)
>  		return 1;
>  
> -	pn->lruvec_stat_local = alloc_percpu(struct lruvec_stat);
> +	pn->lruvec_stat_local = alloc_percpu_gfp(struct lruvec_stat,
> +						 GFP_KERNEL_ACCOUNT);
>  	if (!pn->lruvec_stat_local) {
>  		kfree(pn);
>  		return 1;
>  	}
>  
> -	pn->lruvec_stat_cpu = alloc_percpu(struct lruvec_stat);
> +	pn->lruvec_stat_cpu = alloc_percpu_gfp(struct lruvec_stat,
> +					       GFP_KERNEL_ACCOUNT);
>  	if (!pn->lruvec_stat_cpu) {
>  		free_percpu(pn->lruvec_stat_local);
>  		kfree(pn);
> @@ -5100,11 +5102,13 @@ static struct mem_cgroup *mem_cgroup_alloc(void)
>  		goto fail;
>  	}
>  
> -	memcg->vmstats_local = alloc_percpu(struct memcg_vmstats_percpu);
> +	memcg->vmstats_local = alloc_percpu_gfp(struct memcg_vmstats_percpu,
> +						GFP_KERNEL_ACCOUNT);
>  	if (!memcg->vmstats_local)
>  		goto fail;
>  
> -	memcg->vmstats_percpu = alloc_percpu(struct memcg_vmstats_percpu);
> +	memcg->vmstats_percpu = alloc_percpu_gfp(struct memcg_vmstats_percpu,
> +						 GFP_KERNEL_ACCOUNT);
>  	if (!memcg->vmstats_percpu)
>  		goto fail;
>  
> @@ -5153,7 +5157,9 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
>  	struct mem_cgroup *memcg;
>  	long error = -ENOMEM;
>  
> +	memalloc_use_memcg(parent);
>  	memcg = mem_cgroup_alloc();
> +	memalloc_unuse_memcg();
>  	if (IS_ERR(memcg))
>  		return ERR_CAST(memcg);
>  
> -- 
> 2.25.4
> 

Acked-by: Dennis Zhou <dennis@kernel.org>

Thanks,
Dennis