Comment # 18 on bug 998850 from Michal Hocko

(In reply to Peter S�tterlin from comment #16)
[...] 
> It is however not doing any memory allocation by itself (at least greping
> for alloc does not give any result).

Allocations done in userspace are not that interesting because those can be
reclaimed by the kernel. Slab allocations are done by kernel and their
reclaimability is more complicated. Userspace might trigger those allocations
inderectly though. Now it is a question whether there is an unexpected usage
which leads to a memory leak or the userspace just pins that memory in some
way.

(In reply to Peter S�tterlin from comment #17)
> Created attachment 692785 [details]
> stacktrace with gkrellm running

We can get a list of syscalls quite easily with the traces:
$ zgrep -i "=> \<SYS" stacktrace.gz | sort | uniq -c
   3171  => SyS_access
      8  => syscall_return_slowpath
      7  => SYSC_connect
      2  => SyS_chdir
      1  => SyS_chmod
      1  => SyS_chown
      2  => SYSC_newfstatat
  13071  => SYSC_newlstat
  23795  => SYSC_newstat
    490  => SYSC_statfs
     61  => SyS_execve
      6  => SyS_fsync
     34  => SyS_getcwd
     65  => SyS_inotify_add_watch
      1  => SyS_mkdir
     40  => SyS_readlink
   2097  => SyS_readlinkat
      2  => SyS_rename

nothing really surprising there. Mostly vfs ones. Just curious does echo 3 >
/proc/sys/vm/drop_caches makes any difference?

We can also check who is calling the allocator then we have basically the same
picture as previously:
$ zgrep -A 1 "=> kmem_cache_alloc" stacktrace.gz | grep -v
"kmem_cache_alloc\|--" | sort | uniq -c
  53432  => getname_flags
     42  => getname_kernel
    164  => mempool_alloc
     34  => SyS_getcwd

most callers should go via names_cachep cache. mempool_alloc users are
    143  => bio_alloc_bioset
       113  => btrfs_bio_alloc
        30  => xfs_add_to_ioend
     13  => __sg_alloc_table
        sg_alloc_table_chained

nothing really that surprising either.

That being said, I do not see anything that could massively leak generic 4k
cache.