Brendan Gregg wrote up a performance comparison between the utilities Top and Prstat. And just for good measure, he throws in a lot of Dtrace example code to show how he came to his conclusions.
Here’s some advice if you notice your system may be having a performance problem. Run the
ls of your
/proc filesystem. This will tell you how many active processes are running on your system.
If you’re dealing with a large process count, consider running either command with a short number of iterations, otherwise your monitoring attempts will only contribute to the overall load. I would argue that in a lot of cases, people running Top or Prstat in a background window are actually contributing to any performance problems that they eventually discover through the use of those tools.