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Date:   Mon, 30 May 2022 14:25:52 +0300
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From:   Vasily Averin <vvs@openvz.org>
Subject: [PATCH mm v3 1/9] memcg: enable accounting for struct cgroup
To:     Andrew Morton <akpm@linux-foundation.org>
Cc:     kernel@openvz.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, Shakeel Butt <shakeelb@google.com>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        =?UTF-8?Q?Michal_Koutn=c3=bd?= <mkoutny@suse.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        Michal Hocko <mhocko@suse.com>,
        Muchun Song <songmuchun@bytedance.com>, cgroups@vger.kernel.org
References: <06505918-3b8a-0ad5-5951-89ecb510138e@openvz.org>
 <cover.1653899364.git.vvs@openvz.org>
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Precedence: bulk

Creating each new cgroup allocates 4Kb for struct cgroup. This is the
largest memory allocation in this scenario and is epecially important
for small VMs with 1-2 CPUs.

Common part of the cgroup creation:
Allocs  Alloc   $1*$2   Sum     Allocation
number  size
--------------------------------------------
16  ~   352     5632    5632    KERNFS
1   +   4096    4096    9728    (cgroup_mkdir+0xe4)
1       584     584     10312   (radix_tree_node_alloc.constprop.0+0x89)
1       192     192     10504   (__d_alloc+0x29)
2       72      144     10648   (avc_alloc_node+0x27)
2       64      128     10776   (percpu_ref_init+0x6a)
1       64      64      10840   (memcg_list_lru_alloc+0x21a)
percpu:
1   +   192     192     192     call_site=psi_cgroup_alloc+0x1e
1   +   96      96      288     call_site=cgroup_rstat_init+0x5f
2       12      24      312     call_site=percpu_ref_init+0x23
1       6       6       318     call_site=__percpu_counter_init+0x22

 '+' -- to be accounted,
 '~' -- partially accounted

Accounting of this memory helps to avoid misuse inside memcg-limited
containers.

Signed-off-by: Vasily Averin <vvs@openvz.org>
Reviewed-by: Roman Gushchin <roman.gushchin@linux.dev>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Acked-by: Shakeel Butt <shakeelb@google.com>
Reviewed-by: Muchun Song <songmuchun@bytedance.com>
---
 kernel/cgroup/cgroup.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 1779ccddb734..1be0f81fe8e1 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -5353,7 +5353,7 @@ static struct cgroup *cgroup_create(struct cgroup *parent, const char *name,
 
 	/* allocate the cgroup and its ID, 0 is reserved for the root */
 	cgrp = kzalloc(struct_size(cgrp, ancestor_ids, (level + 1)),
-		       GFP_KERNEL);
+		       GFP_KERNEL_ACCOUNT);
 	if (!cgrp)
 		return ERR_PTR(-ENOMEM);
 
-- 
2.36.1