Gitlab CE is overutilized



My gitlab instance is already overutilized as like below,

  1. 25K Active users
  2. 32K projects
  3. 4K groups
  4. 56 CPU core
  5. 252 GB Memory
    Gitlab Version : 10.6.4

And facing severe performance issue such as enqueued jobs more than 25K which is making delay in all execution in sidekiq.

Could anyone can help me to fine tune the current environment for better performance.