Is ubuntu swap enabled

I have installed ubuntu in my computer, later, I format a partition as linux swap and want to replace it with existing tmp directory under mount point /. I followed procedure given in this link: http://ubuntuforums.org/showthread.php?t=1670222 . The question is that the swap is still not enabled. Here is some command output.

shijiex@shijie-ThinkPad-T410:~$ df 
Filesystem     1K-blocks     Used Available Use% Mounted on
/dev/sda1       28703740  5324096  21914916  20% /
tmpfs            1180916      924   1179992   1% /run
.........
/dev/sda7       28706812 17150036  10091896  63% /home
shijiex@shijie-ThinkPad-T410:~$ sudo blkid -c /dev/null -o list 
device         fs_type  label     mount point        UUID
-----------------------------------------------------------------------
/dev/sda1      ext4               /                  47d9205b-00a8-40e5-88d6-e8b9571799a7
...
/dev/sda7      ext4               /home              e2ae897d-62b1-45d3-a17a-49e7a1b8fbe7
/dev/sda9      swap               <swap>             81ce2033-4ff2-4e05-9500-aacfd1019855

shijiex@shijie-ThinkPad-T410:~$ sudo mount
/dev/sda1 on / type ext4 (rw,errors=remount-ro)
udev on /dev type devtmpfs (rw,mode=0755)
devpts on /dev/pts type devpts (rw,noexec,nosuid,gid=5,mode=0620)
tmpfs on /run type tmpfs (rw,noexec,nosuid,size=10%,mode=0755)
 ......
/dev/sda8 on /opt type ext4 (rw)
/dev/sda5 on /backup type ext4 (rw)
/dev/sda6 on /other type ext4 (rw)
/dev/sda7 on /home type ext4 (rw)
binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,noexec,nosuid,nodev)
gvfs-fuse-daemon on /home/shijiex/.gvfs type fuse.gvfs-fuse-daemon (rw,nosuid,nodev,user=shijiex)

At the end of /etc/fstab, it is:

# swap was on /dev/sda9 during installation
UUID=81ce2033-4ff2-4e05-9500-aacfd1019855  none            swap    sw              0       0

shijiex@shijie-ThinkPad-T410:~$ df 
Filesystem     1K-blocks     Used Available Use% Mounted on
/dev/sda1       28703740  5324100  21914912  20% /
udev             2942940        4   2942936   1% /dev
tmpfs            1180916      924   1179992   1% /run
none                5120        0      5120   0% /run/lock
none             2952280      156   2952124   1% /run/shm

/dev/sda8 14286320 11978284 1575672 89% /opt /dev/sda5 38317716 36097448 267144 100% /backup /dev/sda6 85532500 35151740 46029084 44% /other /dev/sda7 28706812 17150392 10091540 63% /home

The swap partition is sda9.I am not sure whether swap is enabled, because:

1. /dev/sda9 is not in list of df result. While previously it always should be like:

   /dev/sda9       28706812 17150392  10091540  63% /tmp
   

2. Gpart shows that /dev/sda9 as linux-swap with 14.85G,

   used     unused 
   --        --
   

3. I was unable to access swap area. Previously, swap was always mount as /tmp and I can access this directory. Now the /tmp is only a directory under /..

4. The OS is ubuntu 12.04 lts..

[UPDATE]:

The swap should have been enabled, cat /proc/swaps:

/dev/sda9                               partition   15575036    0   -1

though the used size is 0.

Now the scenario is:

I already have tmp directory under /, how can I mount swap this partition as mount point is /tmp. I modified last line of fstab as:

UUID=81ce2033-4ff2-4e05-9500-aacfd1019855  /tmp            swap    sw              0       0

Then mount -a and reboot does not report any error. But used in swap is 0 though I dumped many file content to /tmp.

So how can I fully utilized swap area, which is almost 15G? It is waste of disk if it always 0 used..

Or how can I just change /tmp to the swap partition?

I want this because this directory is widely used in my program and it is also as exchange area between my Ubuntu and hosted WindowXP. Both requires large disk space..