Why Is The Swap Usage High Even Though The Memory Shows 50% Or More Free?

Why is the swap usage is high even though the memory is 50% or more free?

• It is normal for Linux to use some swap, even if there is a free space in RAM.
• There are many processes that require in-memory state for at least the time a request is being processed.
• This is loaded to main memory. As and when its complete, processes like Radius and Policy server will move on to other requests.
• Unused portions of memory are offloaded to swap just incase there is a request to load it back to memory.
• If not loaded for a while, it will be removed / replaced in swap also.
• It is not an issue as swap cannot grow beyond its limit.