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

Dennis Zhou
2020-06-05T19:54:36Z

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);