[cespare]

My conclusion at the time was that it was not, strictly speaking, a bug. It seemed to be a sharp edge that was WAI.

Considering it again now, I do think it's essentially a bug, but it seems to be a known thing at this point. What I described is the same issue addressed by this unmerged patch: https://lkml.org/lkml/2017/9/18/739 (see discussion here: https://lwn.net/Articles/814535/). And it's mentioned in the article in this HN link:

> Those dentries still take up valuable memory, and they can create other problems (such as soft lockups) as well.

[bcrl]

Even if it's just a performance anomaly, these are good reports for kernel developers to have. If nothing else, it helps expand developers' understanding of the sorts of workloads people have had problems with. In the case of really complex systems, it can take a number of reports to spot the pattern, or in the case of proposed fixes, enough pains points to justify the risk of making a change. A report like this takes 60 seconds to cut and paste into an email to a mailing list. Or use the kernel.org bugzilla that is triaged by helpful volunteers. Every voice counts.