cpu performance

Hi,

My Server is R710 Poweredge, sometimes my server run slow, I try to check the performance from task manager it shows that cpu performance on 80% and memory on 70%. But on the CPU usage history show only the left bar display show full performance but the others still empty. It is also happened on the memory physical usage history. Why does not all bar show an activities?

And what is the best solution of the problems?

Thanks,

Joe