memory 8G, swap:8G
after adding 8G memory, the swap doesn't work
how can I activate it?
OS: CentOS 7, 64bit.
The Swap is configured correctly and we can see it in the image posted.
There is no separate step to activate swap. Swap is used only when system runs out of RAM. Your system has enough RAM for all the running applications.
The image you have posted shows that there is 7.75GB of swap and not used.