From http://www.ncrunch.net/download/showChangeLog?version=2.17, specifically
Added a warning for systems using early versions of .NET 4.6 under x64, where a serious GC performance
issue exists.
I got this warning on my local machine when building (it would be good if these hotfix links were provided in changelist as well perhaps?), but what about grid nodes? Will it show up in "Errors" tab when applicable or how should I deduce if I need to do something with my grid node machines?
The grid nodes don't detect this problem, but they aren't as heavily affected by it. The amount of algorithmic processing on the nodes by NCrunch is actually very low - they mostly just spawn processes and call into user code. I would expect that there is no action you need to take here, but if you have tests that run under x64 and churn lots of memory, it may be worth installing the hotfix on your nodes.