I think they're actually talking about blowing out the dentry cache, but sure IO contention is anoyher shared resource in containers. Depending on what you're doing you might run into issues in various networking limits (somaxconns comes to mind, as does what's left of the route cache), blowing out the page cache, or something eating up your memory bandwidth (maybe via some unlucky NUMA).

All for containers but they don't solve the hard problems folks often ascribe to them, really just shows in most cases you don't need to solve the hard problems. Most of the time what containers are buying you is an easy deployment method that leverages some nice features in the OS to make believe you're on separate machines.