mm: memcontrol: allow to disable kmem accounting for cgroup2

Kmem accounting might incur overhead that some users can't put up with.
Besides, the implementation is still considered unstable.  So let's
provide a way to disable it for those users who aren't happy with it.

To disable kmem accounting for cgroup2, pass cgroup.memory=nokmem at
boot time.

Signed-off-by: Vladimir Davydov <vdavydov@virtuozzo.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt
index 3ea869d7a31c4019c0ed768050b930a370931521..cfb2c0f1a4a89237ce131999d7b1cc03aff178b4 100644 (file)
--- a/Documentation/kernel-parameters.txt
+++ b/Documentation/kernel-parameters.txt
@@ -611,6 +611,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
        cgroup.memory=  [KNL] Pass options to the cgroup memory controller.
                        Format: <string>
                        nosocket -- Disable socket memory accounting.
+                       nokmem -- Disable kernel memory accounting.
 
        checkreqprot    [SELINUX] Set initial checkreqprot flag value.
                        Format: { "0" | "1" }

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 9e7a4e5219170955bc640dd1dc43b15bc2b174e7..2239e6dd4d4c12a9153aec137c7e404d175b07de 100644 (file)
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -83,6 +83,9 @@ struct mem_cgroup *root_mem_cgroup __read_mostly;
 /* Socket memory accounting disabled? */
 static bool cgroup_memory_nosocket;
 
+/* Kernel memory accounting disabled? */
+static bool cgroup_memory_nokmem;
+
 /* Whether the swap controller is active */
 #ifdef CONFIG_MEMCG_SWAP
 int do_swap_account __read_mostly;
@@ -2925,8 +2928,8 @@ static int memcg_propagate_kmem(struct mem_cgroup *memcg)
         * onlined after this point, because it has at least one child
         * already.
         */
-       if (cgroup_subsys_on_dfl(memory_cgrp_subsys) ||
-           memcg_kmem_online(parent))
+       if (memcg_kmem_online(parent) ||
+           (cgroup_subsys_on_dfl(memory_cgrp_subsys) && !cgroup_memory_nokmem))
                ret = memcg_online_kmem(memcg);
        mutex_unlock(&memcg_limit_mutex);
        return ret;
@@ -5638,6 +5641,8 @@ static int __init cgroup_memory(char *s)
                        continue;
                if (!strcmp(token, "nosocket"))
                        cgroup_memory_nosocket = true;
+               if (!strcmp(token, "nokmem"))
+                       cgroup_memory_nokmem = true;
        }
        return 0;
 }