如何增加虚拟内存?

[root@rhels5532 ~]# umount tmpfs

[root@rhels5532 ~]# mount -t tmpfs shmfs -o size=3000m /dev/shm
[root@rhels5532 ~]# df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda1              26G  4.3G   20G  19% /
shmfs                 3.0G     0  3.0G   0% /dev/shm

LABEL=/                 /                       ext3    defaults        1 1
tmpfs                   /dev/shm                tmpfs   size=3000m        0 0
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
sysfs                   /sys                    sysfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0
LABEL=SWAP-sda2         swap                    swap    defaults        0 0
~