我怎样才能增加记忆力？

Question

我是 ubuntu 新手。我使用的是 ubuntu 14.04 LTS。我遇到了这个错误

Physical memory usage is too high: physicalBytes = 3G > maxPhysicalBytes = 3G

使用此命令

dmidecode -t 16

我有

# dmidecode 2.12
SMBIOS 2.7 present.

Handle 0x0012, DMI type 16, 23 bytes
Physical Memory Array
Location: System Board Or Motherboard
Use: System Memory
Error Correction Type: None
Maximum Capacity: 32 GB
Error Information Handle: 0x0019
Number Of Devices: 4

使用命令free得到

             total       used       free     shared    buffers     cached
Mem:       8069552    7872888     196664     908496     248808    5355856
-/+ buffers/cache:    2268224    5801328
Swap:      4086780          0    4086780

我该如何解决它？