I have got 2 machine, both updated 21.7.4, both are showing the same symptom. There is an ifconfig command taking up 1-3 cpu cores. The CPU Core shows pegged in all monitoring. Rebooting makes no difference, and trying to kill the pid returns not found. I backed up and reinstalled the whole OS and the issue immediately returned.
ifconfig command taking up 1-3 cpu cores
For future setups if possible I would prefer an Intel x700 series card (ixl) as these have been proven to be stable in our experience.
Installed an x520 card over here with an ixgbe driver, the issue is reproducible and definitely related to the driver. On my end ifconfig -v operates normally as soon as I insert modules into the empty slots, which seems to point to some missing detection when trying to read the i2c bus (which is only possible when there is a module inserted).Can you try to install sfp+ modules (or cables) and check if the issue is gone when all slots are occupied?
the issue with 'slow' output from ifconfig -m -v is still present with the x540-t2 ( with both ports connected and good link ) - so it's NOT a sfp+/i2c issue - it's a driver issue
If you think you have more experience about why this isn't an i2c issue, please feel free to fix the driver so we can all conclude that the timeout happens for no reason (which I obviously don't expect, with all the time I have spend on this in the last days debugging it).
how about you actually bother reading intel's tech docs - the x520 line has i2c to talk to the sfp+ modules - the x540 with it's integrated phy has NO i2c - so if the problem exhibits on both platforms you're not looking at an i2c bug
on hardenedBSD you get a pause with with ifconfig -v to an x540-t2 - and no different output with/without the -v option - it's like the hBSD ix driver is always querying i2c (and hitting a timeout) even when it's not appropriate to that model card