BIG-IP uses SWAP memory though TMM memory is free?

Also understand that a BIG-IP is always running TWO concurrent operating systems. The Traffic Management OS (TMOS), often referred to as the "data plane", is where traffic management happens, iRules, and client-sever data flow. Then you have the "HMS" as it's being referred to here. It's a Linux-based OS used for bootstrapping TMOS and for generic "management plane" functions - cron jobs, external monitors, the Apache/mod_ssl/PAM/MCP services used by the management GUI, the iControl interface, and the management and provisioning hooks into TMOS. No client-server data passes through the management plane. When the system boots, TMOS reserves the lion's share of total system memory, leaving a very small chunk for the management subsystem. If you use one of the typical Linux-based tools to look at memory and processes (i.e. ps, top), you're going to see what the management plane sees. You have to look from within TMOS to see what's being used inside the reserved memory space.