请教一下，docker info提示WARNING: No swap limit support,的意思？

请教一下各位，我在虚拟机(ubuntu15.04,64bit,内核4.0)装完docker后，用docker info ,显示：WARNING: No swap limit support,这句话有什么特别的意思吗？如果是我的虚拟机配置问题，那又需要作哪些改动呢。
root@localhost:~# docker info
Containers: 0
Images: 0
Storage Driver: devicemapper
Pool Name: docker-252:0-657575-pool
Pool Blocksize: 65.54 kB
Backing Filesystem: extfs
Data file: /dev/loop0
Metadata file: /dev/loop1
Data Space Used: 305.7 MB
Data Space Total: 107.4 GB
Data Space Available: 14.27 GB
Metadata Space Used: 729.1 kB
Metadata Space Total: 2.147 GB
Metadata Space Available: 2.147 GB
Udev Sync Supported: false
Data loop file: /var/lib/docker/devicemapper/devicemapper/data
Metadata loop file: /var/lib/docker/devicemapper/devicemapper/metadata
Library Version: 1.02.82-git (2013-10-04)
Execution Driver: native-0.2
Kernel Version: 4.0.0-040000-generic
Operating System: Ubuntu 15.04
CPUs: 4
Total Memory: 1.937 GiB
Name: localhost
ID: VNWE:SZ46:IZGD:FX26:NRKQ:CU72:GE2E:OVYD:52D7:UA5P:LQ46:WFBB
WARNING: No swap limit support收起