When should irqbalance not be installed ?

[zarak]

irqbalance aims to have better performances on a machine by distributing IRQs on all cores. This sounds like a good idea and got me questioned why this is not the default behavior for linux and/or main distribution like debian ?
Does it somehow bring some drawback(s) that are yet unclear to me, or could I install blindly irqbalance everywhere and expect it to help, or in the worst case scenario to not do anything ?

Thanks for the clarification,

[Neil Horman]

you should never do anything blindly and expect things to be "Better" for whatever definition you are considering for the term better.

First irqbalance doesn't aim to provide consistent (and hopefully improved) performance compared to a system that is similarly loaded in which IRQ affinity is assigned by hardware. That may not be optimal performance however, nor may it be the performance you want. for instance, you may have an rdma adapter for which irqs for transmission and reception are commonly paired on the same CPU to create memory affinity. It will work without that, but at a performance cost. Irqbalance is typically unaware of this hardware specific need, and so often additional irqbalance configuration is needed

likewise, if you are running a hard real time system, you may want to isolate all your interrupts to a single CPU (accepting the performance penalty), so that your remaining cpus can behave a realtime fashion, without additional latency jitter from unexpected interrupts