How to see the CPU usage of Linux processes as percentage in Grafana?

Test environment:
Grafana : Version 5.1.3
Simple-json-datasource
Collectd-5.8.0
grafana-rrd-server

Query 1:
I am using collectd to capture the CPU, process metrics and plotting in Grafana using SimpleJson.
In grafana, I am able to plot the graph of ps_cputime.rrd of individual processes. Currently, the user and system CPU time are plotted as 2 graphs. Is it possible to combine these two into a single graph so that the total CPU usage of the process will be displayed as a sum of user and system CPU time?

Query 2:
Collectd Process plugin reports the CPU time in microseconds of user and system for each processes. The value is microseconds of used CPU per second of real time. The output is in RRD format and I am using SimpleJson datasource to see the graph in Grafana. Is there any mechanism to convert the CPU time in microseconds to percentage, using garfana? [like applying the formula : (value * 100)/1000000 ]

Hi All,
I think graphite datasource support options to sum the user and system CPU time and to calculate the percentage value. so I am trying that option.