Server is swapping regardless of available memory

Here is some vmstat output

x@x-server:~$ vmstat 1
procs -----------memory---------- ---swap-- -----io---- -system-- ------cpu-----
 r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
 1  0 223104 123116  67944 521656    0    1     3     4   16   32  1  0 99  0  0
 0  0 223104 123116  67944 521656    0    0     0     0   38   74  0  0 100  0  0
 0  0 223104 123116  67944 521656    0    0     0     0   31   64  0  0 100  0  0
 0  0 223104 122944  67944 521560    0    0     0     0  126  145  1  0 99  0  0
 0  0 223052 122820  67944 521560   64    0    72     0   83  145  0  1 98  0  0
 0  0 223000 122820  67944 521560   64    0    64     0   60  114  1  0 99  1  0
 0  0 223000 122820  67944 521560    0    0     0     0   44   78  0  1 100  0  0
 0  0 223000 122820  67944 521560    0    0     0     0   27   56  0  0 100  0  0
 0  0 223000 122820  67952 521552    0    0     0    24   82  145  0  0 100  0  0
 0  0 223000 122820  67952 521560    0    0     0     0   42   86  0  1 100  0  0
 0  0 222952 122696  67952 521560   32    0    32     0   75  127  1  0 100  0  0
 0  0 222952 122696  67952 521560    0    0     0     0   28   58  0  0 100  0  0
 0  0 222896 122448  67952 521560   48    0    48     0   90  127  1  0 99  0  0
 0  0 222896 122448  67952 521560    0    0     0     0   31   63  0  1 100  0  0
 0  0 222896 122448  67952 521560    0    0     0     0   31   62  0  0 100  0  0

And here is free

x@x-server:~$ free -m
              total        used        free      shared  buff/cache   available
Mem:           1430         734         119          25         575         636
Swap:          1467         217        1250

As you can see I got some swap action going on even though I got a bunch of memory (around 50%) available. Why is that and how can I make it use that memory?

In order to determine which process is using the swap memory use this below command and check. If you don't wanted that process kill it and proceed

for file in /proc/*/status ; do awk '/VmSwap|Name/{printf $2 " " $3}END{ print ""}' $file; done | sort -k 2 -n -r | less