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Date: Wed, 16 Jun 2021 18:53:09 +0800
From: Muchun Song <songmuchun@...edance.com>
To: Matthew Wilcox <willy@...radead.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...nel.org>,
Vladimir Davydov <vdavydov.dev@...il.com>,
Shakeel Butt <shakeelb@...gle.com>,
Roman Gushchin <guro@...com>, Yang Shi <shy828301@...il.com>,
Alex Shi <alexs@...nel.org>,
Wei Yang <richard.weiyang@...il.com>,
Dave Chinner <david@...morbit.com>,
trond.myklebust@...merspace.com, anna.schumaker@...app.com
Cc: linux-fsdevel <linux-fsdevel@...r.kernel.org>,
LKML <linux-kernel@...r.kernel.org>,
Linux Memory Management List <linux-mm@...ck.org>,
linux-nfs@...r.kernel.org, zhengqi.arch@...edance.com,
Xiongchun duan <duanxiongchun@...edance.com>,
fam.zheng@...edance.com
Subject: Re: [PATCH v2 00/21] Optimize list lru memory consumption
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@...edance.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
>
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