Re: [PATCH v4 00/17] Optimize list lru memory consumption

From: Muchun Song
Date: Fri Dec 17 2021 - 06:07:12 EST

On Fri, Dec 17, 2021 at 6:05 PM xiaoqiang zhao
<zhaoxiaoqiang007@xxxxxxxxx> wrote:
>
>
>
> 在 2021/12/14 0:53, Muchun Song 写道:
> > This series is based on Linux 5.16-rc3.
> >
> > 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.
>
> IIUC, you mean: "the memory consumption of kmalloc-32 slab cache is
> caused by list_lru_one allocation"

Right.

>
> >
> > 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. It leads to 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.
> >
> > 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 1 | 21957 MB | <--------+
> > +-----------------------+------------------------+ |
> > | after patch 11 | 6895 MB | |
> > +-----------------------+------------------------+ |
> > | after patch 13 | 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@xxxxxxxxxxxxx/
> > [2] https://lore.kernel.org/linux-fsdevel/20210405054848.GA1077931@xxxxxxxxxx/
> >
> > This series not only optimizes the memory usage of list_lru but also
> > simplifies the code.
> >
> > Changelog in v4:
> > - Remove some code cleanup patches since they are already merged.
> > - Collect Acked-by from Theodore.
> > - Fix ntfs3 (Thanks Argillander).
> >
> > Changelog in v3:
> > - Fix mixing advanced and normal XArray concepts (Thanks to Matthew).
> > - Split one patch into per-filesystem patches.
> >
> > Changelog in v2:
> > - Update Documentation/filesystems/porting.rst suggested by Dave.
> > - Add a comment above alloc_inode_sb() suggested by Dave.
> > - Rework some patch's commit log.
> > - Add patch 18-21.
> >
> > Thanks Dave.
> >
> > Muchun Song (17):
> > mm: list_lru: optimize memory consumption of arrays of per cgroup
> > lists
> > mm: introduce kmem_cache_alloc_lru
> > fs: introduce alloc_inode_sb() to allocate filesystems specific inode
> > fs: allocate inode by using alloc_inode_sb()
> > f2fs: allocate inode by using alloc_inode_sb()
> > nfs42: use a specific kmem_cache to allocate nfs4_xattr_entry
> > 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
> > mm: memcontrol: move memcg_online_kmem() to mem_cgroup_css_online()
> > 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 +
> > block/bdev.c | 2 +-
> > 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/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 | 8 +-
> > 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/ntfs3/super.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 | 2 +-
> > fs/zonefs/super.c | 2 +-
> > include/linux/fs.h | 11 +
> > include/linux/list_lru.h | 17 +-
> > include/linux/memcontrol.h | 42 ++--
> > include/linux/slab.h | 3 +
> > include/linux/swap.h | 5 +-
> > include/linux/xarray.h | 9 +-
> > ipc/mqueue.c | 2 +-
> > lib/xarray.c | 10 +-
> > mm/list_lru.c | 423 ++++++++++++++++------------------
> > mm/memcontrol.c | 164 +++----------
> > mm/shmem.c | 2 +-
> > mm/slab.c | 39 +++-
> > mm/slab.h | 25 +-
> > mm/slob.c | 6 +
> > mm/slub.c | 42 ++--
> > mm/workingset.c | 2 +-
> > net/socket.c | 2 +-
> > net/sunrpc/rpc_pipe.c | 2 +-
> > 76 files changed, 486 insertions(+), 539 deletions(-)
> >