Comment 18 for bug 1833322

Hi Ethanay
> All I can find is a recommendation not to use it on CPUs with 2 or fewer
> cores as the overhead is said to be too high

This isn't a real problem anyway, the service will stop immediately if only
running on one core - even if running on multiple cores with the same
cache (as the intended benefit is due to cache hotness by having all I/O
hitting the same cache).

> I can imagine it might still add undesirable or even critical latency in
> applications that are highly latency sensitive

I understand your line of thought, but it might even improve latency.
If there is no bottleneck on the cores assigned to handle an IRQ then
the improved cache hit rate will make even latency better.
And if there is a strong bottleneck, then some drivers without IRQbalance
would end up locked on one cpu - so again these might gain lower latency.
But I have no data on this either (just like no one seems to have on almost
any of this).

Just like others I'd personally more expect the drawback to be on a potential
lack of power saving.

> This website gave me some clarity on the theory and purpose:
> https://www.baeldung.com/linux/irqbalance-modern-hardware

Hah, didn't find this one yet - thank you!
But to me it only underlines the "it can help as much or even more often"
expectation.