Zotac CI323 Nano hdac0 Interrupt Storm Mitigation
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In case this may help someone else, I noticed unusually high CPU usage following my upgrade to 2.4.4, and top showed that it was due to a very high rate of interrupts from hdac0. To be quite honest, I'm not certain that this coincided with the 2.4.4 upgrade, or if I've just been so oblivious that I never noticed until now. But since hdac0 is just Intel HDA Audio, and therefore of no particular use to a firewall, it can be disabled by adding the following line to /boot/loader.conf.local:
hint.hdac.0.disabled=1