On a Debian Linux 3.16 machine, I have 244 MB of swap space used:
# free -h
total used free shared buffers cached
Mem: 94G 36G 57G 1.9G 3.8G 11G
-/+ buffers/cache: 20G 73G
Swap: 487M 244M 243M
Looking at this, I cannot find 244 MB used.
# for file in /proc/*/status ; do grep VmSwap $file; done | sort -nk 2 | tail
VmSwap: 0 kB
VmSwap: 0 kB
VmSwap: 0 kB
VmSwap: 0 kB
VmSwap: 0 kB
VmSwap: 0 kB
VmSwap: 4 kB
VmSwap: 12 kB
VmSwap: 16 kB
VmSwap: 36 kB
And I only have 34 MB of SwapCached
:
# grep -i swap /proc/meminfo
SwapCached: 34584 kB
SwapTotal: 499708 kB
SwapFree: 249388 kB
Kernel doc says about this:
SwapCached: Memory that once was swapped out, is swapped back in but still also is in the swapfile (if memory is needed it doesn't need to be swapped out AGAIN because it is already in the swapfile. This saves I/O)
How can I know which process is using my swap space on my Linux system? More precisely: Where are consumed each of those 244 MB of swap?
SwapCached
can also be seen as stuff that was swapped out, and was later needed. And you don't have much swapped out, and can not have much swapped out. Why do you have a swap space at all?