Spring Websocket with SimpleMessage Broker taking huge CPU usage while Processing messages to clients

I am working on spring WebSocket with SimpleMessage Broker (enabled Stomp Protocol). I am testing my WebSocket application from JMeter where I can make more than 3k connections successfully with my WebSocket server but when I send a message from my WebSocket server to connected clients that takes huge CPU utilization until the message broadcast get finished. So can anyone please help me out to tune the CPU usage in this case?