Ubuntu high memory and CPU usage

[mahesh]

Hey everybody. I am already doing pentesting for firms.
My laptop is 8gb ram, 256 ssd, 3GHZ new huawei d15. So i wanted to know exactly I have so much CPU( 80-90%) even on Windows and Memory usage (50-60) while on activity with ubuntu with pentesting tools.
I am using Ubuntu through VirtualBo.. While installing i made, Memory Base 4096 MB , Processors 3 of 4 and Video Memory is 128(max). My question is how to use ubuntu on Virtual machine with perfect settings or Using ubuntu with live usb ?
Anyone tell me if i am setting upped ubuntu storage wrong