Here is an excellent article written by Chris Nauroth on how to tune GC.
Here is another guide that explains the relative file objects size and GC settings.
Since you mentioned pause as an issue, this might help you.
sandeep vura <[hidden email]>
Date: Tuesday, September 13, 2016 at 6:11 AM
To: "[hidden email]" <[hidden email]>
Subject: Pause duration alert on Name Node
Hi Hadoop experts,
We are getting continuous Pause duration alert from Standby NN.
Current configuration for Java heap size of NN : 7.8 GB
When we checked NN webUI heap memory used 7.5 GB of 7.8 GB heap memory.
Please suggest how to fix this.