[PATCH 0/9] Shrink the list lru size on memory cgroup removal

Muchun Song
2021-04-28T09:54:05Z

In our server, we found a suspected memory leak problem. The kmalloc-32
consumes more than 6GB of memory. Other kmem_caches consume less than 2GB
memory.

After our in-depth analysis, the memory consumption of kmalloc-32 slab
cache is the cause of list_lru_one allocation.

crash> p memcg_nr_cache_ids
memcg_nr_cache_ids = $2 = 24574

memcg_nr_cache_ids is very large and memory consumption of each list_lru
can be calculated with the following formula.

num_numa_node * memcg_nr_cache_ids * 32 (kmalloc-32)

There are 4 numa nodes in our system, so each list_lru consumes ~3MB.

crash> list super_blocks | wc -l
952

Every mount will register 2 list lrus, one is for inode, another is for
dentry. There are 952 super_blocks. So the total memory is 952 * 2 * 3
MB (~5.6GB). But the number of memory cgroup is less than 500. So I
guess more than 12286 containers have been deployed on this machine (I
do not know why there are so many containers, it may be a user's bug or
the user really want to do that). But now there are less than 500
containers in the system. And memcg_nr_cache_ids has not been reduced
to a suitable value. This can waste a lot of memory. If we want to reduce
memcg_nr_cache_ids, we have to reboot the server. This is not what we
want.

So this patchset will dynamically adjust the value of memcg_nr_cache_ids
to keep healthy memory consumption. In this case, we may be able to restore
a healthy environment even if the users have created tens of thousands of
memory cgroups and then destroyed those memory cgroups. This patchset also
contains some code simplification.

Muchun Song (9):
mm: list_lru: fix list_lru_count_one() return value
mm: memcontrol: remove kmemcg_id reparenting
mm: list_lru: rename memcg_drain_all_list_lrus to
memcg_reparent_list_lrus
mm: memcontrol: remove the kmem states
mm: memcontrol: move memcg_online_kmem() to mem_cgroup_css_online()
mm: list_lru: support for shrinking list lru
ida: introduce ida_max() to return the maximum allocated ID
mm: memcontrol: shrink the list lru size
mm: memcontrol: rename memcg_{get,put}_cache_ids to
memcg_list_lru_resize_{lock,unlock}

include/linux/idr.h | 1 +
include/linux/list_lru.h | 2 +-
include/linux/memcontrol.h | 15 ++----
lib/idr.c | 40 +++++++++++++++
mm/list_lru.c | 89 +++++++++++++++++++++++++--------
mm/memcontrol.c | 121 +++++++++++++++++++++++++--------------------
6 files changed, 183 insertions(+), 85 deletions(-)

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2.11.0