advice on xruns

Anyone have an in depth treatise on xruns and how to minimize them. By 
that I dont mean just adjusting the buffer size, I mean really getting 
into the gears of why xruns happen and how to potentially minimize them.

Reason I ask is that I use jack on a live music basis amd it is crucial 
for me to get no more than 2.9ms latency.
I can hear and feel every latency above above that.

I am lucky with mixbus and jack on Linux to get 2.9ms with the 
occasional xrun every 2 minutes, but I want to see if I cannot eliminate 
them.

Any advice or point to very relevant reference material will be 
appreciated.

Thanks