That sounds like you could have hit transparent hugepage / compaction related issues. They, IME, tend to hit more often with lots of long running processes, tha

That sounds like you could have hit transparent hugepage / compaction related issues. They, IME, tend to hit more often with lots of long running processes, than when there's a lot of churn. It has gotten a lot better in more recent kernel versions, but if you're on an older kernel, it can be really bad.