Only advice I can give you is to remove modules that you don’t need. I’ve seen an increase in reload times for v15, so just depends on hardware and installed modules.
Forgive me, but I haven’t set any configuration settings to use swap, so I’m not sure why we are seeing usage. Our newest FPBX installation (ver16) isn’t using any swap.
I wouldn’t modify the settings as they are. It’s biting into swap, most likely due to memory allocation. I’m not an expert on the topic, but you’ll definitely get into swap space if you don’t have enough RAM. Try clearing it out so your swap usage shows 0 via htop. Then try again. Swap usage = you’re using disk when you ought to be using RAM.
A well dimension-ed machine doesn’t ever NEED swap space
An under dimension-ed machine without swapspace might well have a kernel OOM crash under load.
Understand the load and when it happens, asterisk when not transcoding or recording does not write to disk, when it is recording or transcoding or doing cron stuff it might.
Install sysstat and logwatch and keep an eye on them to see when your machine might be low resourced.