It all depends on how much data you would like to keep and monitor. If you're going to keep data let's say for last minute, last hour and last 24 hours (100 data points each) you'll be fine. It will extend base memory footprint by about 4MB approx basing on my experiments. When it comes to CPU, these operations are not so expensive and consume up to 0.1% of my Macbook Pro power (on default settings which are 3 series of 60 datapoints)