Better Kernel Virtual Memory Parameters

Under a load of 200 calls, all to IVRs or Voicemail, we started hearing audio artifact that could be described as "clicking" and "stuttering".

Under load testing, it was determined that virtual memory defaults are not optimized for heavy disk loads generated by database and recording/playback. I changed the parameters to those recommended by RedHat for use with Oracle db in this doc: https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/6/html/Performance_Tuning_Guide/s-memory-tunables.html and the issue improved significantly.

Here's what I set in /etc/sysctl.conf:
vm.swappiness = 10
vm.dirty_ratio = 15
vm.dirty_background_ratio = 3

These should probably be the default on the distro.