Re: [PATCH v2 00/21] Optimize list lru memory consumption

[Muchun Song <songmuchun@bytedance.com>]

I'm very sorry to bother everyone. Ping guys. Any comments on this series?

On Thu, May 27, 2021 at 2:24 PM Muchun Song <songmuchun@bytedance.com> wrote:
>
> 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 now the number of memory cgroups is less than 500. So I
> guess more than 12286 memory cgroups have been created on this machine (I
> do not know why there are so many cgroups, it may be a user's bug or
> the user really want to do that). Because 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.
>
> In order to reduce memcg_nr_cache_ids, I had posted a patchset [1] to do
> this. But this did not fundamentally solve the problem.
>
> We currently allocate scope for every memcg to be able to tracked on every
> superblock instantiated in the system, regardless of whether that superblock
> is even accessible to that memcg.
>
> These huge memcg counts come from container hosts where memcgs are confined
> to just a small subset of the total number of superblocks that instantiated
> at any given point in time.
>
> For these systems with huge container counts, list_lru does not need the
> capability of tracking every memcg on every superblock.
>
> What it comes down to is that the list_lru is only needed for a given memcg
> if that memcg is instatiating and freeing objects on a given list_lru.
>
> As Dave said, "Which makes me think we should be moving more towards 'add the
> memcg to the list_lru at the first insert' model rather than 'instantiate
> all at memcg init time just in case'."
>
> This patchset aims to optimize the list lru memory consumption from different
> aspects.
>
> Patch 1-6 are code simplification.
> Patch 7 converts the array from per-memcg per-node to per-memcg
> Patch 8 is code simplification.
> Patch 9-15 let list_lru allocation dynamically.
> Patch 16 is code cleanup.
> Patch 17 use xarray to optimize per memcg pointer array size.
> Patch 18-21 is code simplification.
>
> I had done a easy test to show the optimization. I create 10k memory cgroups
> and mount 10k filesystems in the systems. We use free command to show how many
> memory does the systems comsumes after this operation (There are 2 numa nodes
> in the system).
>
>         +-----------------------+------------------------+
>         |      condition        |   memory consumption   |
>         +-----------------------+------------------------+
>         | without this patchset |        24464 MB        |
>         +-----------------------+------------------------+
>         |     after patch 7     |        21957 MB        | <--------+
>         +-----------------------+------------------------+          |
>         |     after patch 15    |         6895 MB        |          |
>         +-----------------------+------------------------+          |
>         |     after patch 17    |         4367 MB        |          |
>         +-----------------------+------------------------+          |
>                                                                     |
>         The more the number of nodes, the more obvious the effect---+
>
> BTW, there was a recent discussion [2] on the same issue.
>
> [1] https://lore.kernel.org/linux-fsdevel/20210428094949.43579-1-songmuchun@bytedance.com/
> [2] https://lore.kernel.org/linux-fsdevel/20210405054848.GA1077931@in.ibm.com/
>
> Changelog in v2:
>   1. Update Documentation/filesystems/porting.rst suggested by Dave.
>   2. Add a comment above alloc_inode_sb() suggested by Dave.
>   2. Rework some patch's commit log.
>   3. Add patch 18-21.
>
>   Thanks Dave.
>
> Muchun Song (21):
>   mm: list_lru: fix list_lru_count_one() return value
>   mm: memcontrol: remove kmemcg_id reparenting
>   mm: memcontrol: remove the kmem states
>   mm: memcontrol: do it in mem_cgroup_css_online to make the kmem online
>   mm: list_lru: remove lru node locking from memcg_update_list_lru_node
>   mm: list_lru: only add the memcg aware lrus to the list_lrus
>   mm: list_lru: optimize the array of per memcg lists memory consumption
>   mm: list_lru: remove memcg_aware field from struct list_lru
>   mm: introduce kmem_cache_alloc_lru
>   fs: introduce alloc_inode_sb() to allocate filesystems specific inode
>   mm: dcache: use kmem_cache_alloc_lru() to allocate dentry
>   xarray: use kmem_cache_alloc_lru to allocate xa_node
>   mm: workingset: use xas_set_lru() to pass shadow_nodes
>   nfs42: use a specific kmem_cache to allocate nfs4_xattr_entry
>   mm: list_lru: allocate list_lru_one only when needed
>   mm: list_lru: rename memcg_drain_all_list_lrus to
>     memcg_reparent_list_lrus
>   mm: list_lru: replace linear array with xarray
>   mm: memcontrol: reuse memory cgroup ID for kmem ID
>   mm: memcontrol: fix cannot alloc the maximum memcg ID
>   mm: list_lru: rename list_lru_per_memcg to list_lru_memcg
>   mm: memcontrol: rename memcg_cache_id to memcg_kmem_id
>
>  Documentation/filesystems/porting.rst |   5 +
>  drivers/dax/super.c                   |   2 +-
>  fs/9p/vfs_inode.c                     |   2 +-
>  fs/adfs/super.c                       |   2 +-
>  fs/affs/super.c                       |   2 +-
>  fs/afs/super.c                        |   2 +-
>  fs/befs/linuxvfs.c                    |   2 +-
>  fs/bfs/inode.c                        |   2 +-
>  fs/block_dev.c                        |   2 +-
>  fs/btrfs/inode.c                      |   2 +-
>  fs/ceph/inode.c                       |   2 +-
>  fs/cifs/cifsfs.c                      |   2 +-
>  fs/coda/inode.c                       |   2 +-
>  fs/dcache.c                           |   3 +-
>  fs/ecryptfs/super.c                   |   2 +-
>  fs/efs/super.c                        |   2 +-
>  fs/erofs/super.c                      |   2 +-
>  fs/exfat/super.c                      |   2 +-
>  fs/ext2/super.c                       |   2 +-
>  fs/ext4/super.c                       |   2 +-
>  fs/f2fs/super.c                       |   2 +-
>  fs/fat/inode.c                        |   2 +-
>  fs/freevxfs/vxfs_super.c              |   2 +-
>  fs/fuse/inode.c                       |   2 +-
>  fs/gfs2/super.c                       |   2 +-
>  fs/hfs/super.c                        |   2 +-
>  fs/hfsplus/super.c                    |   2 +-
>  fs/hostfs/hostfs_kern.c               |   2 +-
>  fs/hpfs/super.c                       |   2 +-
>  fs/hugetlbfs/inode.c                  |   2 +-
>  fs/inode.c                            |   2 +-
>  fs/isofs/inode.c                      |   2 +-
>  fs/jffs2/super.c                      |   2 +-
>  fs/jfs/super.c                        |   2 +-
>  fs/minix/inode.c                      |   2 +-
>  fs/nfs/inode.c                        |   2 +-
>  fs/nfs/nfs42xattr.c                   |  95 ++++----
>  fs/nilfs2/super.c                     |   2 +-
>  fs/ntfs/inode.c                       |   2 +-
>  fs/ocfs2/dlmfs/dlmfs.c                |   2 +-
>  fs/ocfs2/super.c                      |   2 +-
>  fs/openpromfs/inode.c                 |   2 +-
>  fs/orangefs/super.c                   |   2 +-
>  fs/overlayfs/super.c                  |   2 +-
>  fs/proc/inode.c                       |   2 +-
>  fs/qnx4/inode.c                       |   2 +-
>  fs/qnx6/inode.c                       |   2 +-
>  fs/reiserfs/super.c                   |   2 +-
>  fs/romfs/super.c                      |   2 +-
>  fs/squashfs/super.c                   |   2 +-
>  fs/sysv/inode.c                       |   2 +-
>  fs/ubifs/super.c                      |   2 +-
>  fs/udf/super.c                        |   2 +-
>  fs/ufs/super.c                        |   2 +-
>  fs/vboxsf/super.c                     |   2 +-
>  fs/xfs/xfs_icache.c                   |   3 +-
>  fs/zonefs/super.c                     |   2 +-
>  include/linux/fs.h                    |  11 +
>  include/linux/list_lru.h              |  18 +-
>  include/linux/memcontrol.h            |  48 ++--
>  include/linux/slab.h                  |   4 +
>  include/linux/swap.h                  |   5 +-
>  include/linux/xarray.h                |   9 +-
>  ipc/mqueue.c                          |   2 +-
>  lib/xarray.c                          |  10 +-
>  mm/list_lru.c                         | 447 +++++++++++++++++-----------------
>  mm/memcontrol.c                       | 185 ++------------
>  mm/shmem.c                            |   2 +-
>  mm/slab.c                             |  39 ++-
>  mm/slab.h                             |  17 +-
>  mm/slub.c                             |  42 ++--
>  mm/workingset.c                       |   2 +-
>  net/socket.c                          |   2 +-
>  net/sunrpc/rpc_pipe.c                 |   2 +-
>  74 files changed, 480 insertions(+), 577 deletions(-)
>
> --
> 2.11.0
>