I guess that's one of the big advantages JVM languages have. Using stuff like Spring or Hibernate (like Grails does), you benefit from thousands of person-hours spent on tuning those libraries and you still get native Java performance.
Obviously there's a price you have to pay for all the things Grails built on top of Spring/Hibernate (in the benchmark it looks like Grails' performance = Spring / 2), but in general, it's still faster than just writing everything in Groovy (Ruby, Python, ...).
Yup. I manage a Grails app where I wanted to speed up performance on a popular part of the app. So I replace the Grails controller with a servlet. I saw a bump in performance.
Obviously there's a price you have to pay for all the things Grails built on top of Spring/Hibernate (in the benchmark it looks like Grails' performance = Spring / 2), but in general, it's still faster than just writing everything in Groovy (Ruby, Python, ...).