That thrashing is probably executable pages getting evicted, and then having to be reloaded from disk when the process resumes. Even with no swap and overcommit disabled, you'll still get thrashing before the OOM killer gets triggered.

I recommend everyone to enable linux's new multi-generational LRU, that can be configured to trigger the OOM when the workingset of the last N deciseconds doesn't fit in memory. And <https://github.com/hakavlad/nohang> has some more suggestions.