Some applications writing files in the /tmp directory can see huge improvements when memory is used instead of disk.
By default in RHEL 7 / CentOS 7, the /tmp directory resides in the logical volume/physical partition associated with /:
# df -k /tmp Filesystem 1K-blocks Used Available Use% Mounted on /dev/mapper/rhel-root 3030800 1069380 1787752 38% /
Here, another way to check the configuration:
# systemctl is-enabled tmp.mount disabled
To change this behavior and put the /tmp directory on tmpfs, type:
# systemctl enable tmp.mount
Now, if you check the new configuration, this is what you get:
# df -k /tmp Filesystem 1K-blocks Used Available Use% Mounted on tmpfs 508988 8 508980 1% /tmp
Remember not to write big files due to the limited space and, obviously, don’t expect persistence across reboots.