Hi,
Please note that this is not a problem, this is how linux works, this is memory that helps to speed up processes, if you wouldn't use this shared memory the server might have to wait until a memory block large enough to fit a service or request, which could take some time.
Don't worry about it using some space. If you do really, really need the space you can alter the /etc/fstab file and set it manually:
- none /dev/shm tmpfs defaults,size=8G 0 0
This comes straight from the link I sent before.
The 8G is the amount of diskspace that will be reserved for this purpose.
After changing the file, restart or remount the filesystem with
- mount -o remount /dev/shm